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1.  Expanded alternative splice isoform profiling of the mouse Cav3.1/α1G T-type calcium channel 
BMC Molecular Biology  2009;10:53.
Background
Alternative splicing of low-voltage-activated T-type calcium channels contributes to the molecular and functional diversity mediating complex network oscillations in the normal brain. Transcript scanning of the human CACNA1G gene has revealed the presence of 11 regions within the coding sequence subjected to alternative splicing, some of which enhance T-type current. In mouse models of absence epilepsy, elevated T-type calcium currents without clear increases in channel expression are found in thalamic neurons that promote abnormal neuronal synchronization. To test whether enhanced T-type currents in these models reflect pathogenic alterations in channel splice isoforms, we determined the extent of alternative splicing of mouse Cacna1g transcripts and whether evidence of altered transcript splicing could be detected in mouse absence epilepsy models.
Results
Transcript scanning of the murine Cacna1g gene detected 12 regions encoding alternative splice isoforms of Cav3.1/α1G T-type calcium channels. Of the 12 splice sites, six displayed homology to the human CACNA1G splice sites, while six novel mouse-specific splicing events were identified, including one intron retention, three alternative acceptor sites, one alternative donor site, and one exon exclusion. In addition, two brain region-specific alternative splice patterns were observed in the cerebellum. Comparative analyses of brain regions from four monogenic absence epilepsy mouse models with altered thalamic T-type currents and wildtype controls failed to reveal differences in Cacna1g splicing patterns.
Conclusion
The determination of six novel alternative splice sites within the coding region of the mouse Cacna1g gene greatly expands the potential biophysical diversity of voltage-gated T-type channels in the mouse central nervous system. Although alternative splicing of Cav3.1/α1G channels does not explain the enhancement of T-type current identified in four mouse models of absence epilepsy, post-transcriptional modification of T-type channels through this mechanism may influence other developmental neurological phenotypes.
doi:10.1186/1471-2199-10-53
PMCID: PMC2696442  PMID: 19480703
2.  Modified Cav1.4 Expression in the Cacna1fnob2 Mouse Due to Alternative Splicing of an ETn Inserted in Exon 2 
PLoS ONE  2008;3(7):e2538.
The Cacna1fnob2 mouse is reported to be a naturally occurring null mutation for the Cav1.4 calcium channel gene and the phenotype of this mouse is not identical to that of the targeted gene knockout model. We found two mRNA species in the Cacna1fnob2 mouse: approximately 90% of the mRNA represents a transcript with an in-frame stop codon within exon 2 of CACNA1F, while approximately 10% of the mRNA represents a transcript in which alternative splicing within the ETn element has removed the stop codon. This latter mRNA codes for full length Cav1.4 protein, detectable by Western blot analysis that is predicted to differ from wild type Cav1.4 protein in a region of approximately 22 amino acids in the N-terminal portion of the protein. Electrophysiological analysis with either mouse Cav1.4wt or Cav1.4nob2 cDNA revealed that the alternatively spliced protein does not differ from wild type with respect to activation and inactivation characteristics; however, while the wild type N-terminus interacted with filamin proteins in a biochemical pull-down experiment, the alternatively spliced N-terminus did not. The Cacna1fnob2 mouse electroretinogram displayed reduced b-wave and oscillatory potential amplitudes, and the retina was morphologically disorganized, with substantial reduction in thickness of the outer plexiform layer and sprouting of bipolar cell dendrites ectopically into the outer nuclear layer. Nevertheless, the spatial contrast sensitivity (optokinetic response) of Cacna1fnob2 mice was generally similar to that of wild type mice. These results suggest the Cacna1fnob2 mouse is not a CACNA1F knockout model. Rather, alternative splicing within the ETn element can lead to full-length Cav1.4 protein, albeit at reduced levels, and the functional Cav1.4 mutant may be incapable of interacting with cytoskeletal filamin proteins. These changes, do not alter the ability of the Cacna1fnob2 mouse to detect and follow moving sine-wave gratings compared to their wild type counterparts.
doi:10.1371/journal.pone.0002538
PMCID: PMC2432030  PMID: 18596967
3.  Genetic variation in CACNA1C affects brain circuitries related to mental illness 
Archives of General Psychiatry  2010;67(9):939-945.
Context
The CACNA1C gene (alpha 1C subunit of the L-type voltage-gated calcium channel) has been identified as a risk gene for both bipolar disorder and schizophrenia but the mechanism of association has not been explored.
Objective
To identify the neural system mechanism that explains the genetic association between the CACNA1C gene and psychiatric illness, using neuroimaging and human brain expression.
Design
We used BOLD fMRI to measure brain activation in circuitries related to bipolar disorder and schizophrenia by comparing CACNA1C genotype groups in healthy subjects. We tested the effect of genotype on mRNA levels of CACNA1C in post-mortem human brain. A case-control analysis was used to determine the association of CACNA1C genotype and schizophrenia.
Setting
National Institutes of Health Clinical Center
Patients
Healthy Caucasian men and women participated in the fMRI study. Post-mortem samples from normal human brains were used for the brain expression study. Patients with schizophrenia and healthy subjects were used in the case-control analysis.
Main Outcome Measures
BOLD fMRI, mRNA levels in post-mortem brain samples, and genetic association with schizophrenia
Results
The risk associated single nucleotide polymorphism (SNP rs1006737) in CACNA1C predicted increased hippocampal activity during emotional processing (puncorr=0.001, pFDR=0.052, Z=3.20) and increased prefrontal activity during executive cognition (puncorr=2.8e-05, pFDR=0.011, Z=4.03). The risk SNP also predicted increased expression of CACNA1C mRNA in human brain (p=0.0017). CACNA1C was associated with schizophrenia in our case-control sample (OR 1.77, p=0.026).
Conclusions
The risk associated SNP in CACNA1C maps to circuitries implicated in genetic risk for both bipolar disorder and schizophrenia. Its effects in human brain expression implicate a molecular and neural systems mechanism for the clinical genetic association.
doi:10.1001/archgenpsychiatry.2010.96
PMCID: PMC3282053  PMID: 20819988
4.  Two novel alleles of tottering with distinct Ca(v)2.1 calcium channel neuropathologies 
Neuroscience  2008;155(1):31-44.
The calcium channel CACNA1A gene encodes the pore-forming, voltage-sensitive subunit of the voltage-dependent calcium Ca(v)2.1 type channel. Mutations in this gene have been linked to several human disorders, including familial hemiplegic migraine, episodic ataxia 2 and spinocerebellar ataxia type 6. The mouse homologue, Cacna1a, is associated with the tottering, Cacna1atg, mutant series. Here we describe two new missense mutant alleles, Cacna1atg-4J and Cacna1aTg-5J. The Cacna1atg-4J mutation is a valine to alanine mutation at amino acid 581, in segment S5 of domain II. The recessive Cacna1atg-4J mutant exhibited the ataxia, paroxysmal dyskinesia and absence seizures reminiscent of the original tottering mouse. The Cacna1atg-4J mutant also showed altered activation and inactivation kinetics of the Ca(v)2.1 channel, not previously reported for other tottering alleles. The semi-dominant Cacna1aTg-5J mutation changed a conserved arginine residue to glutamine at amino acid 1252 within segment S4 of domain III. The heterozygous mouse was ataxic and homozygotes rarely survived. The Cacna1aTg-5J mutation caused a shift in both voltage activation and inactivation to lower voltages, showing that this arginine residue is critical for sensing Ca(v)2.1 voltage changes. These two tottering mouse models illustrate how novel allelic variants can contribute to functional studies of the Ca(v)2.1 calcium channel.
doi:10.1016/j.neuroscience.2008.05.028
PMCID: PMC2633778  PMID: 18597946
tottering alleles; Ca(v)2.1 calcium channels; semi-dominant mutation
5.  CACNA1C gene polymorphisms, cardiovascular disease outcomes and treatment response 
Background
The gene encoding the target of calcium channel blockers, the α1c-subunit of the L-type calcium channel (CACNA1C) has not been well characterized and only small pharmacogenetic studies testing this gene have been published to date.
Methods and Results
Resequencing of CACNA1C was performed followed by a nested case-control study of the INternational VErapamil SR/trandolapril STudy (INVEST) GENEtic Substudy (INVEST-GENES). Of 46 polymorphisms identified, eight were assessed in the INVEST-GENES. Rs1051375 was found to have a significant interaction with treatment strategy (p=0.0001). Rs1051375 A/A genotype was associated with a 46% reduction in the primary outcome among those randomized to verapamil SR treatment compared to atenolol treatment (OR 0.54 95% CI 0.32-0.92). In heterozygous A/G individuals, there was no difference in the occurrence of the primary outcome when randomized to verapamil SR versus atenolol treatment (OR 1.47 95% CI 0.86-2.53), while homozygous G/G individuals had a greater than 4-fold increased risk of the primary outcome with verapamil treatment compared to those randomized to atenolol treatment (OR 4.59 95% CI 1.67-12.67). We did not identify allelic expression imbalance or differences in mRNA expression in heart tissue by rs1051375 genotype.
Conclusions
Variation in CACNA1C is associated with treatment response among hypertensive patients with stable coronary artery disease. Our data suggest a genetically-defined group of patients that benefit most from calcium channel blocker therapy, a group that benefits most from β-blocker therapy, and a third group in which calcium channel blocker and β-blocker therapy are equivalent.
doi:10.1161/CIRCGENETICS.109.857839
PMCID: PMC2761685  PMID: 20031608
genetics; pharmacology; ion channels; calcium; pharmacogenetics
6.  Functional Properties of a New Voltage-dependent Calcium Channel α2δ Auxiliary Subunit Gene (CACNA2D2)* 
The Journal of biological chemistry  2000;275(16):12237-12242.
We have positionally cloned and characterized a new calcium channel auxiliary subunit, α2δ-2 (CACNA2D2), which shares 56% amino acid identity with the known α2δ-1 subunit. The gene maps to the critical human tumor suppressor gene region in chromosome 3p21.3, showing very frequent allele loss and occasional homozygous deletions in lung, breast, and other cancers. The tissue distribution of α2δ-2 expression is different from α2δ-1, and α2δ-2 mRNA is most abundantly expressed in lung and testis and well expressed in brain, heart, and pancreas. In contrast, α2δ-1 is expressed predominantly in brain, heart, and skeletal muscle. When co-expressed (via cRNA injections) with α1B and β3 subunits in Xenopus oocytes, α2δ-2 increased peak size of the N-type Ca2+ currents 9-fold, and when co-expressed with α1C or α1G subunits in Xenopus oocytes increased peak size of L-type channels 2-fold and T-type channels 1.8-fold, respectively. Anti-peptide antibodies detect the expression of a 129-kDa α2δ-2 polypeptide in some but not all lung tumor cells. We conclude that the α2δ-2 gene encodes a functional auxiliary subunit of voltage-gated Ca2+ channels. Because of its chromosomal location and expression patterns, CACNA2D2 needs to be explored as a potential tumor suppressor gene linking Ca2+ signaling and lung, breast, and other cancer pathogenesis. The homologous location on mouse chromosome 9 is also the site of the mouse neurologic mutant ducky (du), and thus, CACNA2D2 is also a candidate gene for this inherited idiopathic generalized epilepsy syndrome.
PMCID: PMC3484885  PMID: 10766861
7.  Meta-Analysis of Public Microarray Datasets Reveals Voltage-Gated Calcium Gene Signatures in Clinical Cancer Patients 
PLoS ONE  2015;10(7):e0125766.
Voltage-gated calcium channels (VGCCs) are well documented to play roles in cell proliferation, migration, and apoptosis; however, whether VGCCs regulate the onset and progression of cancer is still under investigation. The VGCC family consists of five members, which are L-type, N-type, T-type, R-type and P/Q type. To date, no holistic approach has been used to screen VGCC family genes in different types of cancer. We analyzed the transcript expression of VGCCs in clinical cancer tissue samples by accessing ONCOMINE (www.oncomine.org), a web-based microarray database, to perform a systematic analysis. Every member of the VGCCs was examined across 21 different types of cancer by comparing mRNA expression in cancer to that in normal tissue. A previous study showed that altered expression of mRNA in cancer tissue may play an oncogenic role and promote tumor development; therefore, in the present findings, we focus only on the overexpression of VGCCs in different types of cancer. This bioinformatics analysis revealed that different subtypes of VGCCs (CACNA1C, CACNA1D, CACNA1B, CACNA1G, and CACNA1I) are implicated in the development and progression of diverse types of cancer and show dramatic up-regulation in breast cancer. CACNA1F only showed high expression in testis cancer, whereas CACNA1A, CACNA1C, and CACNA1D were highly expressed in most types of cancer. The current analysis revealed that specific VGCCs likely play essential roles in specific types of cancer. Collectively, we identified several VGCC targets and classified them according to different cancer subtypes for prospective studies on the underlying carcinogenic mechanisms. The present findings suggest that VGCCs are possible targets for prospective investigation in cancer treatment.
doi:10.1371/journal.pone.0125766
PMCID: PMC4493072  PMID: 26147197
8.  Splice isoform-specific suppression of the CaV2.1 variant underlying Spinocerebellar ataxia type 6 
Neurobiology of disease  2011;43(3):533-542.
Spinocerebellar ataxia type 6 (SCA6) is an inherited neurodegenerative disease caused by a polyglutamine (polyQ) expansion in the CaV2.1 voltage-gated calcium channel subunit (CACNA1A). There is currently no treatment for this debilitating disorder and thus a pressing need to develop preventative therapies. RNA interference (RNAi) has proven effective at halting disease progression in several models of spinocerebellar ataxia (SCA), including SCA types 1 and 3. However, in SCA6 and other dominantly inherited neurodegenerative disorders, RNAi-based strategies that selectively suppress expression of mutant alleles may be required. Using a CaV2.1 mini-gene reporter system, we found that pathogenic CAG expansions in CaV2.1 enhance splicing activity at the 3′end of the transcript, leading to a CAG repeat length-dependent increase in the levels of a polyQ-encoding CaV2.1 mRNA splice isoform and the resultant disease protein. Taking advantage of this molecular phenomenon, we developed a novel splice isoform-specific (SIS)-RNAi strategy that selectively targets the polyQ-encoding CaV2.1 splice variant. Selective suppression of transiently expressed and endogenous polyQ-encoding CaV2.1 splice variants was achieved in a variety of cell-based models including a human neuronal cell line, using a new artificial miRNA-like delivery system. Moreover, the efficacy of gene silencing correlated with effective intracellular recognition and processing of SIS-RNAi miRNA mimics. These results lend support to the preclinical development of SIS-RNAi as a potential therapy for SCA6 and other dominantly inherited diseases.
doi:10.1016/j.nbd.2011.04.016
PMCID: PMC3169420  PMID: 21550405
9.  Alternative splicing: Functional diversity among voltage-gated calcium channels and behavioral consequences☆ 
Biochimica et biophysica acta  2012;1828(7):1522-1529.
Neuronal voltage-gated calcium channels generate rapid, transient intracellular calcium signals in response to membrane depolarization. Neuronal CaV channels regulate a range of cellular functions and are implicated in a variety of neurological and psychiatric diseases including epilepsy, Parkinson’s disease, chronic pain, schizophrenia, and bipolar disorder. Each mammalian Cacna1 gene has the potential to generate tens to thousands of CaV channels by alternative pre-mRNA splicing, a process that adds fine granulation to the pool of CaV channel structures and functions. The precise composition of CaV channel splice isoform mRNAs expressed in each cell are controlled by cell-specific splicing factors. The activity of splicing factors are in turn regulated by molecules that encode various cellular features, including cell-type, activity, metabolic states, developmental state, and other factors. The cellular and behavioral consequences of individual sites of CaV splice isoforms are being elucidated, as are the cell-specific splicing factors that control splice isoform selection. Altered patterns of alternative splicing of CaV pre-mRNAs can alter behavior in subtle but measurable ways, with the potential to influence drug efficacy and disease severity. This article is part of a Special Issue entitled: Calcium channels.
doi:10.1016/j.bbamem.2012.09.018
PMCID: PMC3625486  PMID: 23022282
Splicing factor; Disease; Chronic pain; Morphine; Synaptic transmission; G protein coupled receptor; Mu-opioid receptor
10.  Spinal morphine but not ziconotide or gabapentin analgesia is affected by alternative splicing of voltage-gated calcium channel CaV2.2 pre-mRNA 
Molecular Pain  2013;9:67.
Presynaptic voltage-gated calcium CaV2.2 channels play a privileged role in spinal level sensitization following peripheral nerve injury. Direct and indirect inhibitors of CaV2.2 channel activity in spinal dorsal horn are analgesic in chronic pain states. CaV2.2 channels represent a family of splice isoforms that are expressed in different combinations according to cell-type. A pair of mutually exclusive exons in the CaV2.2 encoding Cacna1b gene, e37a and e37b, differentially influence morphine analgesia. In mice that lack exon e37a, which is enriched in nociceptors, the analgesic efficacy of intrathecal morphine against noxious thermal stimuli is reduced. Here we ask if sequences unique to e37a influence: the development of abnormal thermal and mechanical sensitivity associated with peripheral nerve injury; and the actions of two other classes of analgesics that owe part or all of their efficacy to CaV2.2 channel inhibition. We find that: i) the analgesic efficacy of morphine, but not ziconotide or gabapentin, is reduced in mice lacking e37a, ii) the induction and maintenance of behaviors associated with sensitization that accompany peripheral nerve injury, do not require e37a-specific sequence, iii) intrathecal morphine, but not ziconotide or gabapentin analgesia to thermal stimuli is significantly lower in wild-type mice after peripheral nerve injury, iv) the analgesic efficacy of ziconotide and gabapentin to mechanical stimuli is reduced following nerve injury, and iv) intrathecal morphine analgesia to thermal stimuli in mice lacking e37a is not further reduced by peripheral nerve injury. Our findings show that the analgesic action of morphine, but not ziconotide or gabapentin, to thermal stimuli is linked to which Cacna1b exon, e37a or e37b, is selected during alternative pre-mRNA splicing.
doi:10.1186/1744-8069-9-67
PMCID: PMC3916075  PMID: 24369063
Voltage-gated calcium channels; Neuropathic pain; Alternative splicing; Morphine; Ziconotide; Gabapentin; Nociception; Analgesia; Spared nerve injury
11.  A novel p.Gly603Arg mutation in CACNA1F causes Åland island eye disease and incomplete congenital stationary night blindness phenotypes in a family 
Molecular Vision  2011;17:3262-3270.
Purpose
To report, for the first time, that X-linked incomplete congenital stationary night blindness (CSNB2A) and Åland island eye disease (AIED) phenotypes coexist in a molecularly confirmed pedigree and to present novel phenotypic characteristics of calcium channel alpha-1F subunit gene (CACNA1F)-related disease.
Methods
Two affected subjects (the proband and his maternal grandfather) and an unaffected obligate carrier (the proband’s mother) underwent detailed ophthalmological evaluation, fundus autofluorescence imaging, and spectral-domain optical coherence tomography. Goldmann visual field assessment and full-field electroretinogram (ERG) were performed in the two affected subjects, and multichannel flash visual evoked potential was performed on the proband. Scotopic 15 Hz flicker ERG series were performed in both affected subjects to evaluate the function of the slow and fast rod pathways. Haplotype analysis using polymorphic microsatellite markers flanking CACNA1F was performed in all three family members. The proband’s DNA was sequenced for mutations in the coding sequence of CACNA1F and nyctalopin (NYX) genes. Segregation analysis was performed in the family.
Results
Both affected subjects had symptoms of nonprogressive nyctalopia since childhood, while the proband also had photophobia. Both cases had a distance visual acuity of 20/50 or better in each eye, normal contrast sensitivity, and an incomplete type of Schubert-Bornschein ERGs. The proband also had high myopia, a mild red-green color deficit, hypopigmented fundus, and foveal hypoplasia with no evidence of chiasmal misrouting. Spectral-domain optical coherence tomography confirmed the presence of foveal hypoplasia in the proband. The clinical phenotype of the proband and his maternal grandfather fit the clinical description of AIED and CSNB2A, respectively. The fundus autofluorescence and the visual fields were normal in both cases; the scotopic 15 Hz flicker ERG demonstrated only fast rod pathway activity in both. Both affected cases shared the same haplotype across CACNA1F. The proband carried a novel hemizygous c.1807G>C mutation (p.G603R) in the CACNA1F gene. The change segregated with the disease phenotypes and was not identified in 360 control chromosomes. No mutations were identified in NYX.
Conclusions
This report of a missense mutation in CACNA1F causing AIED and CSNB2A phenotypes in a family confirms that both diseases are allelic and that other genetic or environmental modifiers influence the expression of CACNA1F. This is the first report to suggest that in CACNA1F-related disease, the rod system activity is predominantly from the fast rod pathways.
PMCID: PMC3244487  PMID: 22194652
12.  A Novel Null Homozygous Mutation Confirms CACNA2D2 as a Gene Mutated in Epileptic Encephalopathy 
PLoS ONE  2013;8(12):e82154.
Contribution to epileptic encephalopathy (EE) of mutations in CACNA2D2, encoding α2δ-2 subunit of Voltage Dependent Calcium Channels, is unclear. To date only one CACNA2D2 mutation altering channel functionality has been identified in a single family. In the same family, a rare CELSR3 polymorphism also segregated with disease. Involvement of CACNA2D2 in EE is therefore not confirmed, while that of CELSR3 is questionable. In a patient with epilepsy, dyskinesia, cerebellar atrophy, psychomotor delay and dysmorphic features, offspring to consanguineous parents, we performed whole exome sequencing (WES) for homozygosity mapping and mutation detection. WES identified extended autozygosity on chromosome 3, containing two novel homozygous candidate mutations: c.1295delA (p.Asn432fs) in CACNA2D2 and c.G6407A (p.Gly2136Asp) in CELSR3. Gene prioritization pointed to CACNA2D2 as the most prominent candidate gene. The WES finding in CACNA2D2 resulted to be statistically significant (p = 0.032), unlike that in CELSR3. CACNA2D2 homozygous c.1295delA essentially abolished α2δ-2 expression. In summary, we identified a novel null CACNA2D2 mutation associated to a clinical phenotype strikingly similar to the Cacna2d2 null mouse model. Molecular and statistical analyses together argued in favor of a causal contribution of CACNA2D2 mutations to EE, while suggested that finding in CELSR3, although potentially damaging, is likely incidental.
doi:10.1371/journal.pone.0082154
PMCID: PMC3864908  PMID: 24358150
13.  Localization of Cacna1s to ON Bipolar Dendritic Tips Requires mGluR6-Related Cascade Elements 
Purpose.
L-type voltage gated calcium channels in retina localize primarily at the presynaptic active zones of photoreceptors and bipolar cells where they modulate glutamate release. However, the pore forming subunit Cacna1s of certain L-type channels is also expressed postsynaptically at the tips of ON bipolar cell dendrites where it colocalizes with mGluR6, but has an unknown function. At these dendritic tips, the components of the mGluR6 signaling cascade cluster together in a macromolecular complex, and each one's localization often depends on that of the others. Thus, we explored if Cacna1s is part of the mGluR6 complex.
Methods.
We determined Cacna1s expression by PCR using an ON bipolar library, by Western blotting, and by standard immunohistochemistry.
Results.
The PCR amplification confirmed expression of the transcript in ON bipolar cells, and Western blotting showed the expected bands. Immunostaining for Cacna1s was stronger in the dendritic tips of rod bipolar cells than in those of ON cone bipolar cells. This staining severely decreased in mice missing various mGluR6 cascade elements (Grm6−/−, Gnao1−/−, Gnb3−/−, Gng13−/−, and Trpm1−/−). During development, the ratio of the number of Cacna1s puncta to the number of presynaptic ribbons followed a sigmoidal pattern, rising rapidly from P13 to P17. The mGluR6 expression preceded that of Cacna1s and RGS11.
Conclusions.
Our results show that the localization and stability of Cacna1s depend on the expression of mGluR6 and its cascade components, and they suggest that Cacna1s is part of the mGluR6 complex. We hypothesize that Cacna1s contributes to light adaptation by permeating calcium.
The pore forming subunit of a L-type voltage gated calcium channel colocalizes with the components of the ON bipolar cell signaling cascade and its localization is dependent on the normal expression of these components.
doi:10.1167/iovs.13-13766
PMCID: PMC3954003  PMID: 24519419
rod bipolar cell; retina; adaptation; mGluR6; signaling cascade
14.  A Novel CaV1.2 N Terminus Expressed in Smooth Muscle Cells of Resistance Size Arteries Modifies Channel Regulation by Auxiliary Subunits*S 
The Journal of biological chemistry  2007;282(40):29211-29221.
Voltage-dependent L-type Ca2+ (CaV1.2) channels are the principal Ca2+ entry pathway in arterial myocytes. CaV1.2 channels regulate multiple vascular functions and are implicated in the pathogenesis of human disease, including hypertension. However, the molecular identity of CaV1.2 channels expressed in myocytes of myogenic arteries that regulate vascular pressure and blood flow is unknown. Here, we cloned CaV1.2 subunits from resistance size cerebral arteries and demonstrate that myocytes contain a novel, cysteine rich N terminus that is derived from exon 1 (termed “exon 1c”), which is located within CACNA1C, the CaV1.2 gene. Quantitative PCR revealed that exon 1c was predominant in arterial myocytes, but rare in cardiac myocytes, where exon 1a prevailed. When co-expressed with α2δ subunits, CaV1.2 channels containing the novel exon 1c-derived N terminus exhibited: 1) smaller whole cell current density, 2) more negative voltages of half activation (V1/2,act) and half-inactivation (V1/2,inact), and 3) reduced plasma membrane insertion, when compared with channels containing exon 1b. β1b and β2a subunits caused negative shifts in the V1/2,act and V1/2,inact of exon 1b-containing CaV1.2α1/α2δ currents that were larger than those in exon 1c-containing CaV1.2α1/α2δ currents. In contrast, β3 similarly shifted V1/2,act and V1/2,inact of currents generated by exon 1b- and exon 1c-containing channels. β subunits isoform-dependent differences in current inactivation rates were also detected between N-terminal variants. Data indicate that through novel alternative splicing at exon 1, the CaV1.2 N terminus modifies regulation by auxiliary subunits. The novel exon 1c should generate distinct voltage-dependent Ca2+ entry in arterial myocytes, resulting in tissue-specific Ca2+ signaling.
doi:10.1074/jbc.M610623200
PMCID: PMC2276565  PMID: 17699517
15.  Gene Splicing of an Invertebrate Beta Subunit (LCavβ) in the N-Terminal and HOOK Domains and Its Regulation of LCav1 and LCav2 Calcium Channels 
PLoS ONE  2014;9(4):e92941.
The accessory beta subunit (Cavβ) of calcium channels first appear in the same genome as Cav1 L-type calcium channels in single-celled coanoflagellates. The complexity of this relationship expanded in vertebrates to include four different possible Cavβ subunits (β1, β2, β3, β4) which associate with four Cav1 channel isoforms (Cav1.1 to Cav1.4) and three Cav2 channel isoforms (Cav2.1 to Cav2.3). Here we assess the fundamentally-shared features of the Cavβ subunit in an invertebrate model (pond snail Lymnaea stagnalis) that bears only three homologous genes: (LCav1, LCav2, and LCavβ). Invertebrate Cavβ subunits (in flatworms, snails, squid and honeybees) slow the inactivation kinetics of Cav2 channels, and they do so with variable N-termini and lacking the canonical palmitoylation residues of the vertebrate β2a subunit. Alternative splicing of exon 7 of the HOOK domain is a primary determinant of a slow inactivation kinetics imparted by the invertebrate LCavβ subunit. LCavβ will also slow the inactivation kinetics of LCav3 T-type channels, but this is likely not physiologically relevant in vivo. Variable N-termini have little influence on the voltage-dependent inactivation kinetics of differing invertebrate Cavβ subunits, but the expression pattern of N-terminal splice isoforms appears to be highly tissue specific. Molluscan LCavβ subunits have an N-terminal “A” isoform (coded by exons: 1a and 1b) that structurally resembles the muscle specific variant of vertebrate β1a subunit, and has a broad mRNA expression profile in brain, heart, muscle and glands. A more variable “B” N-terminus (exon 2) in the exon position of mammalian β3 and has a more brain-centric mRNA expression pattern. Lastly, we suggest that the facilitation of closed-state inactivation (e.g. observed in Cav2.2 and Cavβ3 subunit combinations) is a specialization in vertebrates, because neither snail subunit (LCav2 nor LCavβ) appears to be compatible with this observed property.
doi:10.1371/journal.pone.0092941
PMCID: PMC3972191  PMID: 24690951
16.  Schizophrenia Related Variants in CACNA1C also Confer Risk of Autism 
PLoS ONE  2015;10(7):e0133247.
Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders with a strong genetic component. Many lines of evidence indicated that ASD shares common genetic variants with other psychiatric disorders (for example, schizophrenia). Previous studies detected that calcium channels are involved in the etiology of many psychiatric disorders including schizophrenia and autism. Significant association between CACNA1C (calcium channel, voltage-dependent, L type, alpha 1C subunit) and schizophrenia was detected. Furthermore, rare mutation in CACNA1C is suggested to cause Timothy syndrome, a multisystem disorder including autism-associated phenotype. However, there is no evidence for association between CACNA1C and autism in Chinese Han population. To investigate the association between single nucleotide polymorphisms (SNP) in CACNA1C and autism, we first performed a family-based association study between eighteen SNPs in CACNA1C and autism in 239 trios. All SNPs were genotyped by using Sequenom genotyping platform. Two SNPs (rs1006737 and rs4765905) have a trend of association with autism. To further confirm the association between these two SNPs with autism, we expanded the sample size to 553 trios by adding 314 trios. Association analyses for SNPs and haplotype were performed by using family-based association test (FBAT) and Haploview software. Permutation tests were used for multiple testing corrections of the haplotype analyses (n=10,000). The significance level for all statistical tests was two-tailed (p<0.05). The results demonstrated that G allele of rs1006737 and G allele of rs4765905 showed a preferential transmission to affected offspring in 553 trios (p=0.035). Haplotype analyses showed that two haplotypes constructed from rs1006737 and rs4765905 were significantly associated with autism (p=0.030, 0.023, respectively; Global p=0.046). These results were still significant after permutation correction (n=10,000, p=0.027). Our research suggests that CACNA1C might play a role in the genetic etiology of autism in Chinese Han population.
doi:10.1371/journal.pone.0133247
PMCID: PMC4512676  PMID: 26204268
17.  Analysis of Maxi-K alpha subunit splice variants in human myometrium 
Background
Large-conductance, calcium-activated potassium (Maxi-K) channels are implicated in the modulation of human uterine contractions and myometrial Ca2+ homeostasis. However, the regulatory mechanism(s) governing the expression of Maxi-K channels with decreased calcium sensitivity at parturition are unclear. The objectives of this study were to investigate mRNA expression of the Maxi-K alpha subunit, and that of its splice variants, in human non-pregnant and pregnant myometrium, prior to and after labour onset, to determine whether altered expression of these splice variants is associated with decreased calcium sensitivity observed at labour onset.
Methods
Myometrial biopsies were obtained at hysterectomy (non-pregnant, NP), and at Caesarean section, at elective (pregnant not-in-labour, PNL) and intrapartum (pregnant in-labour, PL) procedures. RNA was extracted from all biopsies and quantitative real-time RT-PCR was used to investigate for possible differential expression of the Maxi-K alpha subunit, and that of its splice variants, between these functionally-distinct myometrial tissue sets.
Results
RT-PCR analysis identified the presence of a 132 bp and an 87 bp spliced exon of the Maxi-K alpha subunit in all three myometrial tissue sets. Quantitative real-time PCR indicated a decrease in the expression of the Maxi-K alpha subunit with labour onset. While there was no change in the proportion of Maxi-K alpha subunits expressing the 87 bp spliced exon, the proportion of alpha subunits expressing the 132 bp spliced exon was significantly increased with labour onset, compared to both non-pregnant and pregnant not-in-labour tissues. An increased proportion of 132 bp exon-containing alpha subunit variants with labour onset is of interest, as channels expressing this spliced exon have decreased calcium and voltage sensitivities.
Conclusions
Our findings suggest that decreased Maxi-K alpha subunit mRNA expression in human myometrium at labour onset, coupled to an increased proportion of Maxi-K channels expressing the 132 bp spliced exon, may be linked to decreased Maxi-K channel calcium and voltage sensitivity, thereby promoting enhanced uterine activity at the time of labour.
doi:10.1186/1477-7827-2-67
PMCID: PMC524189  PMID: 15383146
18.  Identification of a novel loss-of-function calcium channel gene mutation in short QT syndrome (SQTS6) 
European Heart Journal  2011;32(9):1077-1088.
Aims
Short QT syndrome (SQTS) is a genetically determined ion-channel disorder, which may cause malignant tachyarrhythmias and sudden cardiac death. Thus far, mutations in five different genes encoding potassium and calcium channel subunits have been reported. We present, for the first time, a novel loss-of-function mutation coding for an L-type calcium channel subunit.
Methods and results
The electrocardiogram of the affected member of a single family revealed a QT interval of 317 ms (QTc 329 ms) with tall, narrow, and symmetrical T-waves. Invasive electrophysiological testing showed short ventricular refractory periods and increased vulnerability to induce ventricular fibrillation. DNA screening of the patient identified no mutation in previously known SQTS genes; however, a new variant at a heterozygous state was identified in the CACNA2D1 gene (nucleotide c.2264G > C; amino acid p.Ser755Thr), coding for the Cavα2δ-1 subunit of the L-type calcium channel. The pathogenic role of the p.Ser755Thr variant of the CACNA2D1 gene was analysed by using co-expression of the two other L-type calcium channel subunits, Cav1.2α1 and Cavβ2b, in HEK-293 cells. Barium currents (IBa) were recorded in these cells under voltage-clamp conditions using the whole-cell configuration. Co-expression of the p.Ser755Thr Cavα2δ-1 subunit strongly reduced the IBa by more than 70% when compared with the co-expression of the wild-type (WT) variant. Protein expression of the three subunits was verified by performing western blots of total lysates and cell membrane fractions of HEK-293 cells. The p.Ser755Thr variant of the Cavα2δ-1 subunit was expressed at a similar level compared with the WT subunit in both fractions. Since the mutant Cavα2δ-1 subunit did not modify the expression of the pore-forming subunit of the L-type calcium channel, Cav1.2α1, it suggests that single channel biophysical properties of the L-type channel are altered by this variant.
Conclusion
In the present study, we report the first pathogenic mutation in the CACNA2D1 gene in humans, which causes a new variant of SQTS. It remains to be determined whether mutations in this gene lead to other manifestations of the J-wave syndrome.
doi:10.1093/eurheartj/ehr076
PMCID: PMC3086900  PMID: 21383000
Arrhythmia; Short QT syndrome; Novel gene mutation; Sudden cardiac death
19.  Abundant L-type calcium channel Cav1.3 (α1D) subunit mRNA is detected in rod photoreceptors of the mouse retina via in situ hybridization 
Molecular Vision  2007;13:764-771.
Purpose
Mutations in the CACNA1F gene encoding the L-type calcium channel pore-forming Cav1.4 (α1F) subunit in humans result in an incomplete form of congenital stationary night blindness (CSNB2) with residual photoreceptor function. It has been postulated that this residual function, at least in part, may be mediated by another L-type calcium channel subunit, Cav1.3 (α1D), expressed within cone photoreceptors. However, the expression of the calcium channel Cav1.3 (α1D) subunit within photoreceptors remains debatable due to discrepancies among the immunohistochemical studies reported in the literature. In order to get around the innate complications of utilizing unproven antibodies and to shed light on this discussion, we investigated the mRNA expression profile for the Cav1.3 (α1D) subunit in the mouse retina.
Methods
In situ hybridization was performed on wild type mouse retinal sections with two independent sets of digoxigenin-11-UTP-labeled Cav1.3 (α1D)-specific sense and antisense cRNA probes. The two probe sets employed correspond to two distinct regions of the Cav1.3 (α1D) subunit mRNA, each encoding a different fragment of the Cav1.3 (α1D) polypeptide. In situ hybridization of wild type mouse brain sections with these same probes was performed as an additional control for specificity.
Results
Abundant L-type calcium channel Cav1.3 (α1D) subunit mRNA expression was confirmed in most cells of the outer nuclear layer using two independent Cav1.3 (α1D)-specific antisense cRNA probes, confirming expression in rod photoreceptors. Cav1.3 (α1D) mRNA expression was also observed within most cells of the inner nuclear layer and ganglion cell layers using these same antisense cRNA probes. No labeling of tissue was observed using either sense cRNA probe. In situ detection of concentrated Cav1.3 (α1D) mRNA expression within the hippocampus and Purkinje and granule cells of the cerebellum of wild type mouse brain with these same probes confirmed specificity of the probes.
Conclusions
Our finding of expression of the L-type calcium channel Cav1.3 (α1D) subunit mRNA in rods substantiates the possibility that this pore-forming subunit may be a competent component of channels mediating the residual photoreceptor responses observed in mutant mice lacking functional Cav1.4 (α1F) subunits and in humans with CSNB2. Furthermore, the combined observations of abundant expression of Cav1.3 (α1D) mRNA in wild type rods and the large reduction in the transmission of photoreceptor responses in mice lacking Cav1.4 (α1F) raises the possibility that Cav1.3 (α1D) protein expression levels, localization, or functioning might be concomitantly altered by disruption of the Cav1.4 (α1F) subunit in rods. To date, no studies of Cav1.3 (α1D) mRNA nor protein expression levels or localization in cacna1f mutant mice or humans with CSNB2 have been published. Our findings warrant such studies to address the abovementioned possibilities. Finally, the observation of Cav1.3 (α1D) mRNA expression in multiple retinal cell types suggests the potential for a broader role for this L-type calcium channel subunit in overall functioning of the normal retina than previously appreciated. We therefore suggest that lesions in either the gene encoding the L-type calcium channel Cav1.3 (α1D) subunit or other molecules that interact with and regulate it may underlie one or more retinopathies with currently unidentified molecular etiologies.
PMCID: PMC2768761  PMID: 17563731
20.  Mutations in the cardiac L-type calcium channel associated with inherited J-wave syndromes and sudden cardiac death 
BACKGROUND
L-type calcium channel (LTCC) mutations have been associated with Brugada syndrome (BrS), short QT (SQT) syndrome, and Timothy syndrome (LQT8). Little is known about the extent to which LTCC mutations contribute to the J-wave syndromes associated with sudden cardiac death.
OBJECTIVE
The purpose of this study was to identify mutations in the α1, β2, and α2δ subunits of LTCC (Cav1.2) among 205 probands diagnosed with BrS, idiopathic ventricular fibrillation (IVF), and early repolarization syndrome (ERS). CACNA1C, CACNB2b, and CACNA2D1 genes of 162 probands with BrS and BrS+SQT, 19 with IVF, and 24 with ERS were screened by direct sequencing.
METHODS/RESULTS
Overall, 23 distinct mutations were identified. A total of 12.3%, 5.2%, and 16% of BrS/BrS+SQT, IVF, and ERS probands displayed mutations in α1, β2, and α2δ subunits of LTCC, respectively. When rare polymorphisms were included, the yield increased to 17.9%, 21%, and 29.1% for BrS/BrS+SQT, IVF, and ERS probands, respectively. Functional expression of two CACNA1C mutations associated with BrS and BrS+SQT led to loss of function in calcium channel current. BrS probands displaying a normal QTc had additional variations known to prolong the QT interval.
CONCLUSION
The study results indicate that mutations in the LTCCs are detected in a high percentage of probands with J-wave syndromes associated with inherited cardiac arrhythmias, suggesting that genetic screening of Cav genes may be a valuable diagnostic tool in identifying individuals at risk. These results are the first to identify CACNA2D1 as a novel BrS susceptibility gene and CACNA1C, CACNB2, and CACNA2D1 as possible novel ERS susceptibility genes.
doi:10.1016/j.hrthm.2010.08.026
PMCID: PMC2999985  PMID: 20817017
Arrhythmia; Calcium; Electrophysiology; Genetics; Ion channels
21.  Association between Genetic Polymorphisms in Cav2.3 (R-type) Ca2+ Channels and Fentanyl Sensitivity in Patients Undergoing Painful Cosmetic Surgery 
PLoS ONE  2013;8(8):e70694.
Individual differences in the sensitivity to fentanyl, a widely used opioid analgesic, lead to different proper doses of fentanyl, which can hamper effective pain treatment. Voltage-activated Ca2+ channels (VACCs) play a crucial role in the nervous system by controlling membrane excitability and calcium signaling. Cav2.3 (R-type) VACCs have been especially thought to play critical roles in pain pathways and the analgesic effects of opioids. However, unknown is whether single-nucleotide polymorphisms (SNPs) of the human CACNA1E (calcium channel, voltage-dependent, R type, alpha 1E subunit) gene that encodes Cav2.3 VACCs influence the analgesic effects of opioids. Thus, the present study examined associations between fentanyl sensitivity and SNPs in the human CACNA1E gene in 355 Japanese patients who underwent painful orofacial cosmetic surgery, including bone dissection. We first conducted linkage disequilibrium (LD) analyses of 223 SNPs in a region that contains the CACNA1E gene using genomic samples from 100 patients, and a total of 13 LD blocks with 42 Tag SNPs were observed within and around the CACNA1E gene region. In the preliminary study using the same 100 genomic samples, only the rs3845446 A/G SNP was significantly associated with perioperative fentanyl use among these 42 Tag SNPs. In a confirmatory study using the other 255 genomic samples, this SNP was also significantly associated with perioperative fentanyl use. Thus, we further analyzed associations between genotypes of this SNP and all of the clinical data using a total of 355 samples. The rs3845446 A/G SNP was associated with intraoperative fentanyl use, 24 h postoperative fentanyl requirements, and perioperative fentanyl use. Subjects who carried the minor G allele required significantly less fentanyl for pain control compared with subjects who did not carry this allele. Although further validation is needed, the present findings show the possibility of the involvement of CACNA1E gene polymorphisms in fentanyl sensitivity.
doi:10.1371/journal.pone.0070694
PMCID: PMC3734060  PMID: 23940630
22.  A Voltage-Gated Calcium Channel Regulates Lysosomal Fusion with Endosomes and Autophagosomes and Is Required for Neuronal Homeostasis 
PLoS Biology  2015;13(3):e1002103.
Autophagy helps deliver sequestered intracellular cargo to lysosomes for proteolytic degradation and thereby maintains cellular homeostasis by preventing accumulation of toxic substances in cells. In a forward mosaic screen in Drosophila designed to identify genes required for neuronal function and maintenance, we identified multiple cacophony (cac) mutant alleles. They exhibit an age-dependent accumulation of autophagic vacuoles (AVs) in photoreceptor terminals and eventually a degeneration of the terminals and surrounding glia. cac encodes an α1 subunit of a Drosophila voltage-gated calcium channel (VGCC) that is required for synaptic vesicle fusion with the plasma membrane and neurotransmitter release. Here, we show that cac mutant photoreceptor terminals accumulate AV-lysosomal fusion intermediates, suggesting that Cac is necessary for the fusion of AVs with lysosomes, a poorly defined process. Loss of another subunit of the VGCC, α2δ or straightjacket (stj), causes phenotypes very similar to those caused by the loss of cac, indicating that the VGCC is required for AV-lysosomal fusion. The role of VGCC in AV-lysosomal fusion is evolutionarily conserved, as the loss of the mouse homologues, Cacna1a and Cacna2d2, also leads to autophagic defects in mice. Moreover, we find that CACNA1A is localized to the lysosomes and that loss of lysosomal Cacna1a in cerebellar cultured neurons leads to a failure of lysosomes to fuse with endosomes and autophagosomes. Finally, we show that the lysosomal CACNA1A but not the plasma-membrane resident CACNA1A is required for lysosomal fusion. In summary, we present a model in which the VGCC plays a role in autophagy by regulating the fusion of AVs with lysosomes through its calcium channel activity and hence functions in maintaining neuronal homeostasis.
A voltage-gated calcium channel required for neurotransmitter release also regulates the fusion of neuronal lysosomes with endosomes and autophagosomes, thereby helping to maintain cellular homeostasis.
Author Summary
Autophagy is a cellular process used by cells to prevent the accumulation of toxic substances. It delivers misfolded proteins and damaged organelles by fusing autophagosomes—organelles formed by a double membrane that surrounds the “debris” to be eliminated—with lysosomes. How this fusion process is regulated during autophagy, however, remains to be established. Here, we analyze this process in flies and mice, and find that loss of different subunits of a specific type of Voltage Gated Calcium Channel (VGCC) leads to defects in lysosomal fusion with autophagosomes in neurons. It was already known that VGCCs control calcium entry at synaptic terminals to promote the fusion of synaptic vesicles with the plasma membrane, and that mutations in the subunits of VGCCs in humans cause neurological diseases. Our data indicate that defects in autophagy and lysosomal fusion are independent of defects in synaptic vesicle fusion and neurotransmitter release, and we show that a specific VGCC is present on lysosomal membranes where it is required for lysosomal fusion with endosomes and autophagosomes. These observations suggest that the fusion events required in autophagy rely on mechanisms similar to those that trigger the fusion of synaptic vesicles with the presynaptic membrane.
doi:10.1371/journal.pbio.1002103
PMCID: PMC4374850  PMID: 25811491
23.  Identification of Common Genetic Variation That Modulates Alternative Splicing 
PLoS Genetics  2007;3(6):e99.
Alternative splicing of genes is an efficient means of generating variation in protein function. Several disease states have been associated with rare genetic variants that affect splicing patterns. Conversely, splicing efficiency of some genes is known to vary between individuals without apparent ill effects. What is not clear is whether commonly observed phenotypic variation in splicing patterns, and hence potential variation in protein function, is to a significant extent determined by naturally occurring DNA sequence variation and in particular by single nucleotide polymorphisms (SNPs). In this study, we surveyed the splicing patterns of 250 exons in 22 individuals who had been previously genotyped by the International HapMap Project. We identified 70 simple cassette exon alternative splicing events in our experimental system; for six of these, we detected consistent differences in splicing pattern between individuals, with a highly significant association between splice phenotype and neighbouring SNPs. Remarkably, for five out of six of these events, the strongest correlation was found with the SNP closest to the intron–exon boundary, although the distance between these SNPs and the intron–exon boundary ranged from 2 bp to greater than 1,000 bp. Two of these SNPs were further investigated using a minigene splicing system, and in each case the SNPs were found to exert cis-acting effects on exon splicing efficiency in vitro. The functional consequences of these SNPs could not be predicted using bioinformatic algorithms. Our findings suggest that phenotypic variation in splicing patterns is determined by the presence of SNPs within flanking introns or exons. Effects on splicing may represent an important mechanism by which SNPs influence gene function.
Author Summary
Genetic variation, through its effects on gene expression, influences many aspects of the human phenotype. Understanding the impact of genetic variation on human disease risk has become a major goal for biomedical research and has the potential of revealing both novel disease mechanisms and novel functional elements controlling gene expression. Recent large-scale studies have suggested that a relatively high proportion of human genes show allele-specific variation in expression. Effects of common DNA polymorphisms on mRNA splicing are less well studied. Variation in splicing patterns is known to be tissue specific, and for a small number of genes has been shown to vary among individuals. What is not known is whether allele-specific splicing events are an important mechanism by which common genetic variation affects gene expression. In this study we show that allele-specific alternative splicing was observed in six out of 70 exon-skipping events. Sequence analysis of the relevant splice sites and of the regions surrounding single nucleotide polymorphisms correlated with the splicing events failed to identify any predictive bioinformatic signals. A genome-wide study of allele-specific splicing, using an experimental rather than a bioinformatic approach, is now required.
doi:10.1371/journal.pgen.0030099
PMCID: PMC1904363  PMID: 17571926
24.  The neuronal splicing factor Nova controls alternative splicing in N-type and P-type CaV2 calcium channels 
Channels (Austin, Tex.)  2010;4(6):483-489.
Many cellular processes are involved in optimizing protein function for specific neuronal tasks; here we focus on alternative pre-mRNA splicing. Alternative pre-mRNA splicing gives cells the capacity to modify and selectively re-balance their existing pool of transcripts in a coordinated way across multiple mRNAs, thereby effecting relatively rapid and relatively stable changes in protein activity. Here we report on and discuss the coordinated regulation of two sites of alternative splicing, e24a and e31a, in P-type CaV2.1 and N-type CaV2.2 channels. These two exons encode 4 and 2 amino acids, respectively, in the extracellular linker regions between transmembrane spanning segments S3 and S4 in domains III and IV of each CaV2 subunit. Recent genome-wide screens of splicing factor-RNA binding events by Darnell and colleagues show that Nova-2 promotes inclusion of e24a in CaV2.2 mRNAs in brain. We review these studies and show that a homologous e24a is present in the CaV2.1 gene, Cacna1a, and that it is expressed in different regions of the nervous system. Nova-2 enhances inclusion of e24a but represses e31a inclusion in CaV2.1 and CaV2.2 mRNAs in brain. It is likely that coordinated alternative pre-mRNA splicing across related CaV2 genes by common splicing factors allows neurons to orchestrate changes in synaptic protein function while maintaining a balanced and functioning system.
PMCID: PMC3047467  PMID: 21150296
N-type; P-type; alternative splicing; Nova; neuronal splicing; splicing factors; intron; exon
25.  The neuronal splicing factor Nova controls alternative splicing in N-type and P-type CaV2 calcium channels 
Channels  2010;4(6):483-489.
Many cellular processes are involved in optimizing protein function for specific neuronal tasks; here we focus on alternative pre-mRNA splicing. Alternative pre-mRNA splicing gives cells the capacity to modify and selectively re-balance their existing pool of transcripts in a coordinated way across multiple mRNAs, thereby effecting relatively rapid and relatively stable changes in protein activity. Here we report on and discuss the coordinated regulation of two sites of alternative splicing, e24a and e31a, in P-type CaV2.1 and N-type CaV2.2 channels. These two exons encode 4 and 2 amino acids, respectively, in the extracellular linker regions between transmembrane spanning segments S3 and S4 in domains III and IV of each CaV2 subunit. Recent genome-wide screens of splicing factor-RNA binding events by Darnell and colleagues show that Nova-2 promotes inclusion of e24a in CaV2.2 mRNAs in brain. We review these studies and show that a homologous e24a is present in the CaV2.1 gene, Cacna1a, and that it is expressed in different regions of the nervous system. Nova-2 enhances inclusion of e24a but represses e31a inclusion in CaV2.1 and CaV2.2 mRNAs in brain. It is likely that coordinated alternative pre-mRNA splicing across related CaV2 genes by common splicing factors allows neurons to orchestrate changes in synaptic protein function while maintaining a balanced and functioning system.
doi:10.4161/chan.4.6.12868
PMCID: PMC3047467  PMID: 21150296
N-type; P-type; alternative splicing; Nova; neuronal splicing; splicing factors; intron; exon

Results 1-25 (1251898)