KCNA10 is a voltage gated potassium channel that is expressed in the inner ear. The localization and function of KCNA10 was studied in a mutant mouse, B6-Kcna10TM45, in which the single protein coding exon of Kcna10 was replaced with a beta-galactosidase reporter cassette. Under the regulatory control of the endogenous Kcna10 promoter and enhancers, beta-galactosidase was expressed in hair cells of the vestibular organs and the organ of Corti. KCNA10 expression develops in opposite tonotopic gradients in the inner and outer hair cells. Kcna10TM45 homozygotes display only a mild elevation in pure tone hearing thresholds as measured by auditory brainstem response (ABR), while heterozygotes are normal. However, Kcna10TM45 homozygotes have absent vestibular evoked potentials (VsEPs) or elevated VsEP thresholds with prolonged peak latencies, indicating significant vestibular dysfunction despite the lack of any overt imbalance behaviors. Our results suggest that Kcna10 is expressed primarily in hair cells of the inner ear, with little evidence of expression in other organs. The Kcna10TM45 targeted allele may be a model of human nonsyndromic vestibulopathy.
KCNA10; inner ear; vestibular dysfunction; Kcna10 knockout mouse
Primary cilia are microtubule-based solitary sensing structures on the cell surface that play crucial roles in cell signaling and development. Abnormal ciliary function leads to various human genetic disorders, collectively known as ciliopathies. Outer dense fiber protein 2 (Odf2) was initially isolated as a major component of sperm-tail fibers. Subsequent studies have demonstrated the existence of many splicing variants of Odf2, including Cenexin1 (Odf2 isoform 9), which bears an unusual C-terminal extension. Strikingly, Odf2 localizes along the axoneme of primary cilia, whereas Cenexin1 localizes to basal bodies in cultured mammalian cells. Whether Odf2 and Cenexin1 contribute to primary cilia assembly by carrying out either concerted or distinct functions is unknown. By taking advantage of odf2−/− cells lacking endogenous Odf2 and Cenexin1, but exogenously expressing one or both of these proteins, we showed that Cenexin1, but not Odf2, was necessary and sufficient to induce ciliogenesis. Furthermore, the Cenexin1-dependent primary cilia assembly pathway appeared to function independently of Odf2. Consistently, Cenexin1, but not Odf2, interacted with GTP-loaded Rab8a, localized to the distal/subdistal appendages of basal bodies, and facilitated the recruitment of Chibby, a centriolar component that is important for proper ciliogenesis. Taken together, our results suggest that Cenexin1 plays a critical role in ciliogenesis through its C-terminal extension that confers a unique ability to mediate primary cilia assembly. The presence of multiple splicing variants hints that the function of Odf2 is diversified in such a way that each variant has a distinct role in the complex cellular and developmental processes.
Cenexin1; Odf2; Rab8a; Chibby; primary cilia; ciliogenesis
Cytoskeletal and focal adhesion abnormalities are observed in several types of cancer, including lung cancer. We have previously reported that paxillin (PXN) was mutated, amplified, and overexpressed in a significant number of lung cancer patient samples, that PXN protein was upregulated in more advanced stages of lung cancer compared with lower stages, and that the PXN gene was also amplified in some pre-neoplastic lung lesions. Among the mutations investigated, we previously found that PXN variant A127T in lung cancer cells enhanced cell proliferation and focal adhesion formation and colocalized with the anti-apoptotic protein B Cell Lymphoma 2 (BCL-2), which is known to localize to the mitochondria, among other sites. To further explore the effects of activating mutations of PXN on mitochondrial function, we cloned and expressed wild-type PXN and variants containing the most commonly occurring PXN mutations (P46S, P52L, G105D, A127T, P233L, T255I, D399N, E423K, P487L, and K506R) in a GFP-tagged vector using HEK-293 human embryonic kidney cells. Utilizing live-cell imaging to systematically study the effects of wild-type PXN vs. mutants, we created a model that recapitulates the salient features of the measured dynamics and conclude that compared with wild-type, some mutant clones confer enhanced focal adhesion and lamellipodia formation (A127T, P233L, and P487L) and some confer increased association with BCL-2, Dynamin-related Protein-1 (DRP-1), and Mitofusion-2 (MFN-2) proteins (P233L and D399N). Further, PXN mutants, through their interactions with BCL-2 and DRP-1, could regulate cisplatin drug resistance in human lung cancer cells. The data reported herein suggest that mutant PXN variants play a prominent role in mitochondrial dynamics with direct implications on lung cancer progression and hence, deserve further exploration as therapeutic targets.
mitochondria; paxillin; gene mutation; cell motility; fission; fusion; mitochondrial dynamics
The outer dense fiber 2 (ODF2) protein is an important component of sperm tail outer dense fiber and localizes at the centrosome. It has been reported that the RO072 ES cell derived homozygote knock out of ODF2 results in an embryonic lethal phenotype, and XL169 ES cell derived heterozygote knock out causes severe defects in sperm tail development. The ODF2s splicing variant, Cenexin1, possesses a C-terminal extension, and the phosphorylation of serine 796 residue in an extended C-terminal is responsible for Plk1 binding. Cenexin1 assembles ninein and causes ciliogenesis in early stages of the cell cycle in a Plk1-independent manner. Alternatively, in the late stages of the cell cycle, G2/M phase, Cenexin1 binds to Plk1 and results in proper mitotic progression. In this study, to identify the in vivo function of Plk1 binding to phosphorylated Cenexin1 S796 residue, and to understand the in vivo functional differences between ODF2 and Cenexin1, we generated ODF2/Cenexin1 S796A/Cenexin1 WT expressing transgenic mice in a RO072 ES cell derived ODF2+/- knock out background. We observed a severe defect of sperm tail development by ectopic expression of Cenexin1 S796A mutant and no phenotypic differences between the ectopic expression of ODF2/Cenexin1 WT in ODF2+/- background and in normal wild type mice.
ODF2; Cenexin1; Cenexin1 S794A; Plk1; ODF2+/- knock out mouse; Sperm tail development
Acute hypoxia causes pulmonary vasoconstriction in part by inhibiting voltage-gated K+ (Kv) channel activity in pulmonary artery smooth muscle cells (PASMC). The hypoxia-mediated decrease in Kv currents (IK(V)) is selective to PASMC; hypoxia has little effect on IK(V) in mesenteric artery smooth muscle cells (MASMC). Functional Kv channels are homo- and/or hetero-tetramers of pore-forming α subunits and regulatory β subunits. KCNA5 is a Kv channel α subunit that forms functional Kv channels in PASMC and regulates resting membrane potential. Here, we show that acute hypoxia selectively inhibits IK(V) through KCNA5 channels in PASMC. Overexpression of the human KCNA5 gene increased IK(V) and caused membrane hyperpolarization in HEK-293, COS-7, and rat MASMC and PASMC. Acute hypoxia did not affect IK(V) in KCNA5-transfected HEK-293 and COS-7. However, overexpression of KCNA5 in PASMC conferred its sensitivity to hypoxia. Reduction of Po2 from 145 to 35 mmHg reduced IK(V) by ~40% in rat PASMC transfected with human KCNA5, but had no effect on IK(V) in KCNA5-transfected rat MASMC (or HEK and COS cells). These results indicate that KCNA5 is an important Kv channel that regulates resting membrane potential, and acute hypoxia selectively reduced KCNA5 channel activity in PASMC relative to MASMC and other cell types. Since Kv channels (including KCNA5) are ubiquitously expressed in PASMC and MASMC, the observation from this study indicates that a hypoxia-sensitive mechanism essential for inhibiting KCNA5 channel activity is exclusively present in PASMC. The divergent effect of hypoxia on IK(V) in PASMC and MASMC may also be due to different expression levels of KCNA5 channels.
membrane potential; K+ channels; vascular smooth muscle; pulmonary
The deregulation of paxillin (PXN) has been involved in the progression and metastasis of different malignancies including colorectal cancer (CRC). miR-137 is frequently suppressed in CRC. PXN is predicted to be a direct target of miR-137 in CRC cells. On this basis, we hypothesized that overexpression of PXN induced by suppression of miR-137 may promote tumor progression and metastasis and predicts poor prognosis. We detected the expression of PXN and miR-137 in clinical tumor tissues by immunohistochemical analysis and real-time PCR, positive PXN staining was observed in 198 of the 247 (80.1%) cases, whereas no or weak PXN staining was observed in the adjacent non-cancerous area. Higher level of PXN messenger RNA (mRNA) and lower level of miR-137 was observed in cancer tissues than adjacent non-cancerous tissues. High expression of PXN and low expression of miR-137 was associated with aggressive tumor phenotype and adverse prognosis. Moreover, the expression of PXN was negatively correlated with miR-137 expression. A dual-luciferase reporter gene assay validated that PXN was a direct target of miR-137. The use of miR-137 mimics or inhibitor could decrease or increase PXN mRNA and protein levels in CRC cell lines. Knockdown of PXN or ectopic expression of miR-137 could markedly inhibit cell proliferation, migration and invasion in vitro and repress tumor growth and metastasis in vivo. Taken together, these results demonstrated that overexpression of PXN induced by suppression of miR-137 promotes tumor progression and metastasis and could serve as an independent prognostic indicator in CRC patients.
Gene clusters are of interest for the understanding of genome evolution since they provide insight in large-scale duplications events as well as patterns of individual gene losses. Vertebrates tend to have multiple copies of gene clusters that typically are only single clusters or are not present at all in genomes of invertebrates. We investigated the genomic architecture and conserved non-coding sequences of vertebrate KCNA gene clusters. KCNA genes encode shaker-related voltage-gated potassium channels and are arranged in two three-gene clusters in tetrapods. Teleost fish are found to possess four clusters. The two tetrapod KNCA clusters are of approximately the same age as the Hox gene clusters that arose through duplications early in vertebrate evolution. For some genes, their conserved retention and arrangement in clusters are thought to be related to regulatory elements in the intergenic regions, which might prevent rearrangements and gene loss. Interestingly, this hypothesis does not appear to apply to the KCNA clusters, as too few conserved putative regulatory elements are retained.
We obtained KCNA coding sequences from basal ray-finned fishes (sturgeon, gar, bowfin) and confirmed that the duplication of these genes is specific to teleosts and therefore consistent with the fish-specific genome duplication (FSGD). Phylogenetic analyses of the genes suggest a basal position of the only intron containing KCNA gene in vertebrates (KCNA7). Sistergroup relationships of KCNA1/2 and KCNA3/6 support that a large-scale duplication gave rise to the two clusters found in the genome of tetrapods. We analyzed the intergenic regions of KCNA clusters in vertebrates and found that there are only a few conserved sequences shared between tetrapods and teleosts or between paralogous clusters. The orthologous teleost clusters, however, show sequence conservation in these regions.
The lack of overall conserved sequences in intergenic regions suggests that there are either other processes than regulatory evolution leading to cluster conservation or that the ancestral regulatory relationships among genes in KCNA clusters have been changed together with their regulatory sites.
Atonal homolog1 (Atoh1) is a bHLH transcription factor essential for inner ear hair cell differentiation. Targeted expression of Atoh1 at various stages in development can result in hair cell differentiation in the ear. However, the level and duration of Atoh1 expression required for proper hair cell differentiation and maintenance remain unknown. We generated an Atoh1 conditional knockout (CKO) mouse line using Tg(Atoh1-cre), in which the cre expression is driven by an Atoh1 enhancer element that is regulated by Atoh1 protein to “self-terminate” its expression. The mutant mice show transient, limited expression of Atoh1 in all hair cells in the ear. In the organ of Corti, reduction and delayed deletion of Atoh1 result in progressive loss of almost all the inner hair cells and the majority of the outer hair cells within three weeks after birth. The remaining cells express hair cell marker Myo7a and attract nerve fibers, but do not differentiate normal stereocilia bundles. Some Myo7a-positive cells persist in the cochlea into adult stages in the position of outer hair cells, flanked by a single row of pillar cells and two to three rows of disorganized Deiters cells. Gene expression analyses of Atoh1, Barhl1 and Pou4f3, genes required for survival and maturation of hair cells, reveal earlier and higher expression levels in the inner compared to the outer hair cells. Our data show that Atoh1 is crucial for hair cell mechanotransduction development, viability, and maintenance and also suggest that Atoh1 expression level and duration may play a role in inner vs. outer hair cell development. These genetically engineered Atoh1 CKO mice provide a novel model for establishing critical conditions needed to regenerate viable and functional hair cells with Atoh1 therapy.
5-Fluorouracil (5-FU) is chemotherapeutic agent widely used for the treatment of colorectal cancer. Unfortunately, advanced colorectal cancer is often resistance to such chemotherapy and poor outcome. An adaptor protein paxillin (PXN) is phosphorylated at Y31/Y118 (pPXN-Y31/Y118) by Src contributes to cell mobility and Ser (S)272 of PXN in LD4 domain is important to the interaction between PXN and Bcl-2. We thus hypothesized that pPXN-Y31/Y118 may be required for Bcl-2 protein stability via PXN interacting with Bcl-2 to confer 5-FU resistance in colorectal cancer. Mechanistically, pPXN-S272 is phosphorylated through pPXN-Y31/Y118-mediated p21 protein-activated kinase 1 (PAK1) activation and pPXN-S272 is required for PXN to interact with Bcl-2. The interaction between PXN and Bcl-2 is essential for Bcl-2 protein stability through phosphorylation of Bcl-2 at S87 (pBcl-2-S87) by pPXN-Y31/Y118-mediated ERK activation. An increase in Bcl-2 expression by PXN is responsible for resistance to 5-FU. The resistance to 5-FU can be abolished by inhibitor of Src and PAK1 or Bcl-2 antagonist in cell and animal models. Among patients, Bcl-2 expression is positively correlated with expression of PXN and pPXN-S272, respectively. Patients with high PXN/high Bcl-2 or high pPXN-S272/high Bcl-2 tumors are commonly to have an unfavorable response to 5-FU-based chemotherapy, compared with patients who have high PXN, high pPXN-S272 or high Bcl-2 tumors alone. Therefore, we suggest that Src, PAK1 or Bcl-2 inhibitor may potentially overcome the resistance of 5-FU-based chemotherapy and consequently to improve outcomes in patients with PXN/Bcl-2 and pPXN-S272/Bcl-2-positive tumors.
Relapse after clinical remission remains a leading cause of cancer-associated death. Although the mechanisms of tumor relapse are complex, the ability of cancer cells to survive physiologic stress is a prerequisite for recurrence. Ewing sarcoma (ES) and neuroblastoma (NB) are aggressive cancers that frequently relapse after initial remission. In addition, both tumors over-express the polycomb group (PcG) proteins BMI-1 and EZH2, which contribute to tumorigenicity. We have discovered that ES and NB resist hypoxic stress-induced death and that survival depends on PcG function. Epigenetic repression of developmental programs is the most well established cancer-associated function of PcG proteins. However, we noted that voltage-gated potassium (Kv) channel genes are also targets of PcG regulation in stem cells. Given the role of potassium in regulating apoptosis, we reasoned that repression of Kv channel genes might play a role in cancer cell survival. Here, we describe our novel finding that PcG-dependent repression of the Kv1.5 channel gene, KCNA5, contributes to cancer cell survival under conditions of stress. We show that survival of cancer cells in stress is dependent upon suppression of Kv1.5 channel function. The KCNA5 promoter is marked in cancer cells with PcG-dependent chromatin repressive modifications that increase in hypoxia. Genetic and pharmacologic inhibition of BMI-1 and EZH2, respectively, restore KCNA5 expression, which sensitizes cells to stress-induced death. In addition, ectopic expression of the Kv1.5 channel induces apoptotic cell death under conditions of hypoxia. These findings identify a novel role for PcG proteins in promoting cancer cell survival via repression of KCNA5.
KCNA5; potassium channel; Kv1.5; polycomb; stress; cancer
To date, no universally effective and safe vaccine has been developed for general human use. Leishmania donovani Peroxidoxin-1 (LdPxn-1) is a member of the antioxidant family of proteins and is predominantly expressed in the amastigote stage of the parasite. The aim of this study was to evaluate the immunogenicity and protective efficacy of LdPxn-1 in BALB/c mice in heterologous DNA-Protein immunization regimen in the presence of fusion murine granulocyte-macrophage colony-stimulating factor (mGMCSF) DNA adjuvant.
Methodology and Principal Findings
A fusion DNA of LdPxn1 and mGMCSF was cloned into a modified pcDNA vector. To confirm the expression in mammalian system, Chinese hamster ovary cells were transfected with the plasmid vector containing LdPxn1 gene. BALB/c mice were immunized twice with pcDNA-mGMCSF-LdPxn-1 or pcDNA-LdPxn1 DNA and boosted once with recombinant LdPxn-1 protein. Three weeks after the last immunization, mice were infected with Leishmania major promastigotes. The result showed that immunization with pcDNA-mGMCSF-LdPxn1 elicited a mixed Th-1/Th-2 immune response with significantly higher production of IFN-γ than controls. Intracellular cytokine staining of antigen-stimulated spleen cells showed that immunization with this antigen elicited significantly higher proportion of CD4+ T cells that express IFN-γ, TNF-α, or IL-2. The antigen also induced significantly higher proportion of multipotent CD4+ cells that simultaneously express the three Th-1 cytokines. Moreover, a significant reduction in the footpad swelling was seen in mice immunized with pcDNA-mGMCSF-LdPxn1 antigen. Expression study in CHO cells demonstrated that pcDNA-mGMCSF-LdPxn-1 was expressed in mammalian system.
The result demonstrates that immunization of BALB/c mice with a plasmid expressing LdPxn1 in the presence of mGMCSF adjuvant elicits a strong specific immune response with high level induction of multipotent CD4+ cells that mediate protection of the mice from Leishmania major infection. To our knowledge, this is the first study showing the vaccine potential of Leishmania peroxidoxin -1.
Leishmaniasis, a disease caused by protozoan parasites under the genus Leishmania, claims the lives of thousands of people annually. It mainly affects people in poor communities in Africa, Asia and South America. Although several drugs are available for the treatment of leishmaniasis, their efficacy is limited by the emergence of drug resistant parasite strains and by the inherent side-effects of some drugs. In light of these challenges, developing effective vaccine is considered as a crucial step in the control and ultimate elimination of the disease. In this study, we have evaluated the potential of the antioxidant Leishmania Peroxidoxin-1 as a candidate vaccine for leishmaniasis. The efficacy of the candidate vaccine was assessed in DNA-Protein immunization strategy in mice. We also investigated the adjuvant role of GMCSF DNA fused with the vaccine antigen in a pcDNA plasmid vector. The result showed that Leishmania Peroxidoxin-1 together with fusion GMCSF adjuvant in a pcDNA plasmid induces a partially protective immune response in mice. Further analysis of the immune response demonstrated that the antigen-adjuvant combination elicits CD4+ T cells that express IFN-γ, TNF-α, or IL-2. The antigen also induced a high frequency of CD4+ T cells that simultaneously express all the three cytokines. The study on samples taken from leishmaniasis patients showed that the recombinant Leishmania Peroxidoxin-1 protein is recognized by and elicit immune response in humans, a crucial requirement in the development of a vaccine.
Autoimmune pancreatitis (AIP), characterized by irregular narrowing of the main pancreatic duct, swelling of the pancreas, and histological evidence of lymphoplasmacytic inflammation by high serum immunoglobulin G4, is distinct from ordinary pancreatitis. However, genetic factors involved in the etiology and pathophysiology of AIP remain unclear. Sixty-four patients with autoimmune pancreatitis (53 men, 11 women; mean age, 62.4 years) and 104 healthy Japanese controls were enrolled in this study. We performed an association analysis using 400 microsatellite markers with an average spacing of 10.8 cM in the genome. We also evaluated the association of AIP with seven single nucleotide polymorphisms (SNPs) within the 20-kb region around the potassium voltage-gated channel, shaker-related subfamily, member 3 gene (KCNA3). We identified six statistically significant markers (D1S2726, D5S410, D6S460, D10S548, D15S128, and D20S186; P < 0.05) related to susceptibility. The surrounding region showing the strong association (P = 7.4 × 10−7, Pc = 0.0015) contained the KCNA3 gene. Further analysis by SNP genotyping in KCNA3 gene revealed that four SNPs (rs2840381, rs1058184, rs2640480, rs1319782) were significantly associated with the AIP susceptibility (P < 0.007). KCNA3 is known to be involved in immunomodulation of autoreactive effector and memory T cell–mediated autoimmune diseases. Our findings provide the first evidence that KCNA3 is associated with AIP and suggest that KCNA3 may influence the risk for AIP.
AIP; autoimmune pancreatitis; SNPs; KCNA3; disease susceptibility
Mice lacking the Kv1.1 potassium channel α subunit encoded by the Kcna1 gene develop recurrent behavioral seizures early in life. We examined the neuropathological consequences of seizure activity in the Kv1.1−/− (“knock-out”) mouse, and explored the effects of injecting a viral vector carrying the deleted Kcna1 gene into hippocampal neurons.
Morphological techniques were used to assess neuropathological patterns in hippocampus of Kv1.1−/− animals. Immunohistochemical and biochemical techniques were used to monitor ion channel expression in Kv1.1−/− brain. Both wild-type and knockout mice were injected (bilaterally into hippocampus) with an HSV1 amplicon vector that contained the rat Kcna1 subunit gene and/or the E.coli lacZ reporter gene. Vector-injected mice were were examined to determine the extent of neuronal infection.
Video/EEG monitoring confirmed interictal abnormalities and seizure occurrence in Kv1.1−/− mice. Neuropathological assessment suggested that hippocampal damage (silver stain) and reorganization (Timm stain) occurred only after animals had exhibited severe prolonged seizures (status epilepticus). Ablation of Kcna1 did not result in compensatory changes in expression levels of other related ion channel subunits. Vector injection resulted in infection primarily of granule cells in hippocampus, but the number of infected neurons was quite variable across subjects. Kcna1 immunocytochemistry showed “ectopic” Kv1.1 α channel subunit expression.
Kcna1 deletion in mice results in a seizure disorder that resembles – electrographically and neuropathologically – the patterns seen in rodent models of temporal lobe epilepsy. HSV1 vector-mediated gene transfer into hippocampus yielded variable neuronal infection
Epilepsy; Gene therapy; Hippocampal pathology; Knock-out; Potassium channel; Seizures
Outer dense fiber 2 (Odf2) is highly expressed in the testis where it encodes a major component of the outer dense fibers of the sperm flagellum. Furthermore, ODF2 protein has recently been identified as a wide-spread centrosomal protein. While the expression of Odf2 highlighted a potential role for this gene in male germ cell development and centrosome function, the in vivo function of Odf2 was not known. We have generated Odf2 knockout mice using an Odf2 gene trapped embryonic stem cell (ESC) line. Insertion of a gene trap vector into exon 9 resulted in a gene that encodes a severely truncated protein lacking a large portion of its predicted coil forming domains as well as both leucine zipper motifs that are required for protein–protein interactions with ODF1, another major component of the outer dense fibers. Although wild-type and heterozygous mice were recovered, no mice homozygous for the Odf2 gene trap insertion were recovered in an extended breeding program. Furthermore, no homozygous embryos were found at the blastocyst stage of embryonic development, implying a critical pre-implantation role for Odf2. We show that Odf2 is expressed widely in adults and is also expressed in the blastocyst stage of preimplantation development. These findings are in contrast with early studies reporting Odf2 expression as testis specific and suggest that embryonic Odf2 expression plays a critical role during preimplantation development in mice.
Odf2; sperm; gene trap; outer dense fibers
Altered expression of paxillin (PXN) is closely linked to the pathogenesis progression, metastasis and prognosis of different malignancies including gastric cancer (GC). Epigenetic silencing of tumor-suppressive microRNAs (miRNAs) is a crucial component of the mechanism underlying activation of oncogenes in tumor. To screen for epigenetically silenced miRNAs which target PXN in GC, we performed bioinformatics algorithms and real-time PCR analysis, and identified miR-212 as the optimum candidate gene. A luciferase reporter gene assay validated that miR-212 directly targets the 3’UTR region of PXN. Importantly, miR-212 levels were inversely correlated with PXN expression in GC cell lines and clinical tumor tissues. The use of miR-212 minics decrease PXN mRNA and protein level in GC cell lines. Moreover, low expression of miR-212 and its promoter hypermethylation were causally related and were associated with aggressive tumor phenotype and adverse prognosis in GC. Restoring mir-212 expression by exogenous mirprecursor molecules transfection or reexpression of endogenous miR-212 treated by 5-aza-2’-deoxycytidine (5-aza) can exert similar effect that reduce GC cells invasion and metastasis abilities in vitro by interacting PXN gene. In addition, 5-aza-induced PXN reduction could be partically blocked by miR-212 inhibitor, resulting in a reversal of weankening cell migration and invasion ability of 5-aza. A rescue experiment and a loss-of-function experiment in vitro and vivo showed that PXN restoration rescues migration and invasion phenotype in miR-212 overexpressed GC cell lines and PXN knockdown blocks GC cells migration and invasion in the presence miR-212 inhibitors. Taken together, our results clearly show that overexpression of PXN induced by methylationsuppressed miR-212 promotes tumor metastasis and invasion, and regulation of miR-212 expression may be a novel therapeutic strategy for gastric cancer.
MiR-212; methylation; gastric cancer; cancer metastasis; cancer invasion; PXN; 5-aza-2’-deoxycytidine
Paxillin (PXN) gene has been reported to act as an oncogene in many malignancies and play important roles in the development of human carcinomas. However, the relationship between the expression of PXN and clinicopathological characteristics in human laryngeal carcinoma remains unclear. This study aimed to examine the expression of PXN, and to evaluate the clinical significance of its expression in human laryngeal squamous cell carcinoma (LSCC). Real-time quantitative PCR (qRT-PCR), Western blotting and immunohistochemistry were performed to analyze the expression of PXN in LSCC tissues and corresponding paracancerous normal tissues. Kaplan-Meier survival and Cox regression analyses were performed to evaluate the prognosis of patients with LSCC. The expression of PXN was significantly higher in LSCC than in matched paracancerous normal tissues. Immunohistochemical analysis was performed in human LSCC samples and the data were correlated with clinicopathologic features. Levels of PXN in LSCC were related to histopathological grade (P = 0.016), Lymph node metastasis (P = 0.029) and TNM stage (P < 0.001). Kaplan-Meier analysis revealed that survival curves of the overall survival of patients with high PXN expression was significantly worse than that of low PXN expression (P = 0.035). Cox regression analysis revealed that PXN expression level was an independent prognostic factor of the overall survival rate of patients with LSCC (P = 0.002). These findings suggest that PXN expression has potential use as a novel biomarker of LSCC patients and may serve as an independent predictive factor for prognosis of LSCC patients.
Laryngeal squamous cell carcinoma; paxillin; prognosis
Outer dense fiber 2 (Odf2) was initially identified as a major component of sperm tail cytoskeleton and later was suggested to be a widespread component of centrosomal scaffold that preferentially associates with the appendages of the mother centrioles in somatic cells. Here we report the identification of two Odf2-related centrosomal components, hCenexin1 and hCenexin1 variant 1, that possess a unique C-terminal extension. Our results showed that hCenexin1 is the major isoform expressed in HeLa cells, whereas hOdf2 is not detectably expressed. Mammalian polo-like kinase 1 (Plk1) is critical for proper mitotic progression, and its association with the centrosome is important for microtubule nucleation and function. Interestingly, depletion of hCenexin1 by RNA interference (RNAi) delocalized Plk1 from the centrosomes and the C-terminal extension of hCenexin1 was crucial to recruit Plk1 to the centrosomes through a direct interaction with the polo-box domain of Plk1. Consistent with these findings, the hCenexin1 RNAi cells exhibited weakened γ-tubulin localization and chromosome segregation defects. We propose that hCenexin1 is a critical centrosomal component whose C-terminal extension is required for proper recruitment of Plk1 and other components crucial for normal mitosis. Our results further suggest that the anti-Odf2 immunoreactive centrosomal antigen previously detected in non-germ line cells is likely hCenexin1.
The organ of Corti, the auditory organ of the inner ear, contains two types of sensory hair cells and at least seven types of supporting cells. Most of these supporting cell types rely on Notch-dependent expression of Hes/Hey transcription factors to maintain the supporting cell fate. Here we show that Notch signaling is not necessary for the differentiation and maintenance of pillar cell fate, that pillar cells are distinguished by Hey2 expression, and that – unlike other Hes/Hey factors – Hey2 expression is Notch-independent. Hey2 is activated by FGF and blocks hair cell differentiation, while mutation of Hey2 leaves pillar cells sensitive to the loss of Notch signaling and allows them to differentiate as hair cells. We speculate that co-option of FGF signaling to render Hey2 Notch-independent, also liberated pillar cells from the need for direct contact with surrounding hair cells, and enabled evolutionary remodeling of the complex cellular mosaic of the inner ear.
FGF20 signaling in mice is required specifically for the differentiation of cochlear outer hair cells, the cells most often damaged during age-related hearing loss.
A large proportion of age-related hearing loss is caused by loss or damage to outer hair cells in the organ of Corti. The organ of Corti is the mechanosensory transducing apparatus in the inner ear and is composed of inner hair cells, outer hair cells, and highly specialized supporting cells. The mechanisms that regulate differentiation of inner and outer hair cells are not known. Here we report that fibroblast growth factor 20 (FGF20) is required for differentiation of cells in the lateral cochlear compartment (outer hair and supporting cells) within the organ of Corti during a specific developmental time. In the absence of FGF20, mice are deaf and lateral compartment cells remain undifferentiated, postmitotic, and unresponsive to Notch-dependent lateral inhibition. These studies identify developmentally distinct medial (inner hair and supporting cells) and lateral compartments in the developing organ of Corti. The viability and hearing loss in Fgf20 knockout mice suggest that FGF20 may also be a deafness-associated gene in humans.
A large proportion of age-related hearing loss is caused by loss or damage to outer hair cells in the organ of Corti. The organ of Corti is a highly specialized structure in the inner ear that is composed of inner hair cells, outer hair cells, and associated supporting cells. Although we understand some of the mechanisms that regulate hair cell versus supporting cell differentiation, the mechanisms that regulate differentiation of inner versus outer hair cells are not known. One potential candidate is fibroblast growth factor (FGF) signaling, which is known to regulate the morphogenesis of many sensory organs, including the organ of Corti. In this study, we find that FGF20 signaling is required at a specific time during development to initiate differentiation of cells in the mouse lateral cochlear compartment (which contains outer hair cells and supporting cells, but not inner hair cells). In the absence of FGF20, mice are deaf, and lateral compartment cells remain undifferentiated and unresponsive to mechanisms that regulate the final stages of differentiation. These findings are significant given the importance of outer hair cells during age-related hearing loss. Our studies also suggest that genetic mutations in FGF20 may result in deafness in humans and that FGF20 may be an important factor for the repair or regeneration of sensory cells in the inner ear.
Hmga2 protein belongs to the non-histone chromosomal high-mobility group (HMG) protein family. HMG proteins have been shown to function as architectural transcription regulators, facilitating enhanceosome formation on a variety of mammalian promoters. Hmga2 are expressed at high levels in embryonic and transformed cells. Terminally differentiated cells, however, have been reported to express only minimal, if any, Hmga2. Our previous affymetrix array data showed that Hmga2 is expressed in the developing and adult mammalian cochleas. However, the spatio-temporal expression pattern of Hmga2 in the murine cochlea remained unknown. In this study, we report the expression of Hmga2 in developing and adult cochleas using immunohistochemistry and quantitative real time PCR analysis. Immunolabeling of Hmga2 in the embryonic, postnatal, and mature cochleas showed broad Hmga2 expression in embryonic cochlea (E14.5) at the level of the developing organ of Corti in differentiating hair cells, supporting cells, in addition to immature cells in the GER and LER areas. By postnatal stage (P0–P3), Hmga2 is predominantly expressed in the hair and supporting cells, in addition to cells in the LER area. By P12, Hmga2 immunolabeling is confined to the hair cells and supporting cells. In the adult ear, Hmga2 expression is maintained in the hair and supporting cell subtypes (i.e. Deiters’ cells, Hensen cells, pillar cells, inner phalangeal and border cells) in the cochlear epithelium. Using quantitative real time PCR, we found a decrease in transcript level for Hmga2 comparable to other known inner ear developmental genes (Sox2, Atoh1, Jagged1 and Hes5) in the cochlear epithelium of the adult relative to postnatal ears. These data provide for the first time the tissue-specific expression and transcription level of Hmga2 during inner ear development and suggest its potential dual role in early differentiation and maintenance of both hair and supporting cell phenotypes.
Episodic ataxia type 1 (EA1) is a monogenic channelopathy caused by mutations of the potassium channel gene KCNA1. Affected individuals carrying the same mutation can exhibit considerable variability in the severity of ataxia, neuromyotonia, and other associated features. We investigated the phenotypic heterogeneity of EA1 in 2 sets of identical twins to determine the contribution of environmental factors to disease severity. One of the mutations was also found in a distantly related family, providing evidence of the influence of genetic background on the EA1 phenotype.
We evaluated 3 families with an EA1 phenotype, 2 of which included monozygotic twins. We sequenced the KCNA1 gene and studied the biophysical consequences of the mutations in HEK cells.
We identified a new KCNA1 mutation in each pair of twins. Both pairs reported striking differences in the clinical severity of symptoms. The F414S mutation identified in one set of twins also occurred in a distantly related family in which seizures complicated the EA1 phenotype. The other twins had an R307C mutation, the first EA1 mutation to affect an arginine residue in the voltage-sensor domain. Both mutants when expressed exerted a dominant-negative effect on wild-type channels.
These results broaden the range of KCNA1 mutations and reveal an unexpectedly large contribution of nongenetic factors to phenotypic variability in EA1. The occurrence of epilepsy in 1 of 2 families with the F414S mutation suggests an interplay of KCNA1 with other genetic factors.
= episodic ataxia type 1.
Paxillin is a LIM domain protein localized at integrin-mediated focal adhesions. Although paxillin is thought to modulate the functions of integrins, little is known about the contribution of paxillin to signaling pathways in platelets. Here, we studied the role of paxillin in platelet activation in vitro and in vivo.
Methods and results
We generated paxillin knockdown (Pxn-KD) platelets in mice by transplanting bone marrow cells transduced with a lentiviral vector carrying a short hairpin RNA sequence, and confirmed that paxillin expression was significantly reduced in platelets derived from the transduced cells. Pxn-KD platelets showed a slight increased in size and augmented integrin αIIbβ3 activation following stimulation of multiple receptors including glycoprotein VI and G protein-coupled receptors. Thromboxane A2 biosynthesis and the release of α-granules and dense granules in response to agonist stimulation were also enhanced in Pxn-KD platelets. However, Pxn-KD did not increase tyrosine phosphorylation or intracellular calcium mobilization. Intravital imaging confirmed that Pxn-KD enhanced thrombus formation in vivo.
Our findings suggest that paxillin negatively regulates several common platelet signaling pathways, resulting in the activation of integrin αIIbβ3 and release reactions.
Platelet; Glycoprotein; Platelet aggregation; Release reaction
Paxillin (PXN) has been found to be aberrantly regulated in various malignancies and involved in tumor growth and invasion. The clinicopathological and prognostic significance of PXN in gastric cancer is still unclear.
The expression of PXN was determined in paired gastric cancer tissues and adjacent normal tissues by Western blotting and real-time PCR. Immunohistochemistry was performed to detect the expression of PXN in 239 gastric cancer patients. Statistical analysis was applied to investigate the correlation between PXN expression and clinicopathological characteristics and prognosis in patients. Additionally, the effects of PXN on gastric cancer cell proliferation and migration were also evaluated.
PXN was up-regulated in gastric cancer tissues and cell lines as compared with adjacent normal tissues and normal gastric epithelial cell line GES-1. Overexpression of PXN was correlated with distant metastasis (P = 0.001) and advanced tumor stage (P = 0.021) in gastric cancer patients. Patients with high PXN expression tended to have poor prognosis compared with patients with low PXN expression (P < 0.001). Multivariate analysis demonstrated that PXN expression was an independent prognostic factor (P = 0.020). Moreover, ectopic expression of PXN promotes cell proliferation and migration in AGS cells whereas knockdown of PXN inhibits cell proliferation and migration in SGC7901 cells.
PXN plays an important role in tumor progression and may be used as a potential prognostic indicator in gastric cancer.
Gastric cancer; Paxillin; Tumor progression; Prognosis
Atonal homolog1 (Atoh1, formerly Math1) is a crucial bHLH transcription factor for inner ear hair cell differentiation. Its absence in embryos results in complete absence of mature hair cells at birth and its misexpression can generate extra hair cells. Thus Atoh1 may be both necessary and sufficient for hair cell differentiation in the ear. Atoh1 null mice die at birth and have some undifferentiated cells in sensory epithelia carrying Atoh1 markers. The fate of these undifferentiated cells in neonates is unknown due to lethality. We use Tg(Pax2-Cre) to delete floxed Atoh1 in the inner ear. This generates viable conditional knockout (CKO) mice for studying the postnatal development of the inner ear without differentiated hair cells. Using in situ hybridization we find that Tg(Pax2-Cre) recombines the floxed Atoh1 prior to detectable Atoh1 expression. Only the posterior canal crista has Atoh1 expressing hair cells due to incomplete recombination. Most of the organ of Corti cells are lost in CKO mice via late embryonic cell deaths. Marker genes indicate that the organ of Corti is reduced to two rows of cells wedged between flanking markers of the organ of Corti (Fgf10 and Bmp4). These two rows of cells (instead of five rows of supporting cells) are positive for Prox1 in neonates. By postnatal day 14 (P14), most of the developing organ of Corti is lost through embryonic cell deaths, with the remaining cells transformed into a flat epithelium with no distinction of any specific cell type. However, some of the remaining organ of Corti cells express Myo7a at late postnatal stages and are innervated by remaining afferent fibers. Initial growth of afferents and efferents in embryos shows no difference between control mice and Tg(Pax2-Cre)::Atoh1 CKO mice. Most afferents and efferents are lost in the CKO mutant before birth, leaving only few basal and a more prominent apical innervation. Afferents focus their projections on patches that express the prosensory specifying gene, Sox2. This pattern of innervation by sensory neurons is maintained at least until P14, but fibers target the few Myo7a positive cells found in later stages.
hair cell differentiation; flat epithelium; organ of Corti; innervation of the ear; conditional deletion; mouse ear mutants
In mammals, six separate sensory regions in the inner ear are essential for hearing and balance function. Each sensory region is made up of hair cells, which are the sensory cells, and their associated supporting cells, both arising from a common progenitor. Little is known about the molecular mechanisms that govern the development of these sensory organs. Notch signaling plays a pivotal role in the differentiation of hair cells and supporting cells by mediating lateral inhibition via the ligands Delta-like 1 and Jagged (JAG) 2. However, another Notch ligand, JAG1, is expressed early in the sensory patches prior to cell differentiation, indicating that there may be an earlier role for Notch signaling in sensory development in the ear. Here, using conditional gene targeting, we show that the Jag1 gene is required for the normal development of all six sensory organs within the inner ear. Cristae are completely lacking in Jag1-conditional knockout (cko) mutant inner ears, whereas the cochlea and utricle show partial sensory development. The saccular macula is present but malformed. Using SOX2 and p27kip1 as molecular markers of the prosensory domain, we show that JAG1 is initially expressed in all the prosensory regions of the ear, but becomes down-regulated in the nascent organ of Corti by embryonic day 14.5, when the cells exit the cell cycle and differentiate. We also show that both SOX2 and p27kip1 are down-regulated in Jag1-cko inner ears. Taken together, these data demonstrate that JAG1 is expressed early in the prosensory domains of both the cochlear and vestibular regions, and is required to maintain the normal expression levels of both SOX2 and p27kip1. These data demonstrate that JAG1-mediated Notch signaling is essential during early development for establishing the prosensory regions of the inner ear.
Deafness and adult-onset hearing loss are significant health problems. In most cases, deafness or vestibular dysfunction results when the sensory cells in the inner ear, known as hair cells, degenerate due to environmental or genetic causes. In the mammalian inner ear, the hair cells and their associated supporting cells can be found in six different patches that have particular functions related to hearing or balance. Unfortunately, unlike in birds or fish, mammalian hair cells show little ability to regenerate, resulting in a permanent hearing or balance disorder when damaged. Here, the authors show that a protein called JAG1, a ligand in the Notch signaling pathway, is required for the normal development of all six sensory regions in the mammalian inner ear. In ears that lacked JAG1, some of the sensory patches were missing completely, whereas others were small and lacked particular cell types. The authors showed that JAG1 is required by the sensory precursors, progenitor cells that give rise to both the hair cells and the supporting cells. By understanding how the sensory areas develop normally, it is hoped that molecular tools can be developed that will aid sensory regeneration in the mammalian inner ear.