Neurofibrillary tangles (NFT) and β-amyloid plaques are the neurological hallmarks of both Alzheimer's disease and an unusual paralytic illness suffered by Chamorro villagers on the Pacific island of Guam. Many Chamorros with the disease suffer dementia, and in some villages one-quarter of the adults perished from the disease. Like Alzheimer's, the causal factors of Guamanian amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC) are poorly understood. In replicated experiments, we found that chronic dietary exposure to a cyanobacterial toxin present in the traditional Chamorro diet, β-N-methylamino-l-alanine (BMAA), triggers the formation of both NFT and β-amyloid deposits similar in structure and density to those found in brain tissues of Chamorros who died with ALS/PDC. Vervets (Chlorocebus sabaeus) fed for 140 days with BMAA-dosed fruit developed NFT and sparse β-amyloid deposits in the brain. Co-administration of the dietary amino acid l-serine with l-BMAA significantly reduced the density of NFT. These findings indicate that while chronic exposure to the environmental toxin BMAA can trigger neurodegeneration in vulnerable individuals, increasing the amount of l-serine in the diet can reduce the risk.
Alzheimer's; amyotrophic lateral sclerosis; l-serine; cyanobacteria; BMAA; tau
Clinicogenetic and pathological studies have shown that mutations of the glucocerebrosidase gene (GBA) are a risk factor for Parkinson’s disease and Lewy body disorders. In the present study, we have identified GBA mutations in 6.8% (4/59) of cases with a pathological diagnosis of diffuse Lewy body disease. Taken with previous studies, it appears that GBA mutations are associated with a more diffuse pattern of Lewy body distribution involving the cerebral cortex than the brainstem/limbic distribution observed in typical Parkinson’s disease.
DLBD; Gaucher; disease; GBA; genetics
We used RNA sequencing to analyze transcript profiles of ten autopsy brain regions from ten subjects. RNA sequencing techniques were designed to detect both coding and non-coding RNA, splice isoform composition, and allelic expression. Brain regions were selected from five subjects with a documented history of smoking and five non-smokers. Paired-end RNA sequencing was performed on SOLiD instruments to a depth of >40 million reads, using linearly amplified, ribosomally depleted RNA. Sequencing libraries were prepared with both poly-dT and random hexamer primers to detect all RNA classes, including long non-coding (lncRNA), intronic and intergenic transcripts, and transcripts lacking poly-A tails, providing additional data not previously available. The study was designed to generate a database of the complete transcriptomes in brain region for gene network analyses and discovery of regulatory variants.
Of 20,318 protein coding and 18,080 lncRNA genes annotated from GENCODE and lncipedia, 12 thousand protein coding and 2 thousand lncRNA transcripts were detectable at a conservative threshold. Of the aligned reads, 52 % were exonic, 34 % intronic and 14 % intergenic. A majority of protein coding genes (65 %) was expressed in all regions, whereas ncRNAs displayed a more restricted distribution. Profiles of RNA isoforms varied across brain regions and subjects at multiple gene loci, with neurexin 3 (NRXN3) a prominent example. Allelic RNA ratios deviating from unity were identified in > 400 genes, detectable in both protein-coding and non-coding genes, indicating the presence of cis-acting regulatory variants. Mathematical modeling was used to identify RNAs stably expressed in all brain regions (serving as potential markers for normalizing expression levels), linked to basic cellular functions. An initial analysis of differential expression analysis between smokers and nonsmokers implicated a number of genes, several previously associated with nicotine exposure.
RNA sequencing identifies distinct and consistent differences in gene expression between brain regions, with non-coding RNA displaying greater diversity between brain regions than mRNAs. Numerous RNAs exhibit robust allele selective expression, proving a means for discovery of cis-acting regulatory factors with potential clinical relevance.
Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-2207-8) contains supplementary material, which is available to authorized users.
RNA sequencing; Brain regions; Differential expression; Allelic expression imbalance; Isoform fraction; Non-coding RNA
We analyzed global patterns of expression in genes related to glutamatergic neurotransmission (glutamatergic genes) in healthy human adult brain before determining the effects of chronic alcohol and cocaine exposure on gene expression in the hippocampus.
RNA-Seq data from ‘BrainSpan’ was obtained across 16 brain regions from nine control adults. We also generated RNA-Seq data from postmortem hippocampus from eight alcoholics, eight cocaine addicts and eight controls. Expression analyses were undertaken of 28 genes encoding glutamate ionotropic (AMPA, kainate, NMDA) and metabotropic receptor subunits, together with glutamate transporters.
The expression of each gene was fairly consistent across the brain with the exception of the cerebellum, the thalamic mediodorsal nucleus and the striatum. GRIN1, encoding the essential NMDA subunit, had the highest expression across all brain regions. Six factors accounted for 84% of the variance in global gene expression. GRIN2B (encoding GluN2B), was up-regulated in both alcoholics and cocaine addicts (FDR corrected p = 0.008). Alcoholics showed up-regulation of three genes relative to controls and cocaine addicts: GRIA4 (encoding GluA4), GRIK3 (GluR7) and GRM4 (mGluR4). Expression of both GRM3 (mGluR3) and GRIN2D (GluN2D) was up-regulated in alcoholics and down-regulated in cocaine addicts relative to controls.
Glutamatergic genes are moderately to highly expressed throughout the brain. Six factors explain nearly all the variance in global gene expression. At least in the hippocampus, chronic alcohol use largely up-regulates glutamatergic genes. The NMDA GluN2B receptor subunit might be implicated in a common pathway to addiction, possibly in conjunction with the GABAB1 receptor subunit.
Alcoholism; RNA-Seq; GRIN2B; GRIN2D; NMDA receptors; GABAB1 receptor subunit; GABBR1; GRIA4; GRIK3; GRM3; GRM4
Noribogaine, a polypharmacological drug with activities at opioid receptors, ionotropic nicotinic receptors, and serotonin reuptake transporters, has been investigated for treatment of substance abuse-related disorders. Smoking cessation has major benefits for both individuals and society, therefore the aim of this study was to evaluate the potential of noribogaine for use as a treatment for nicotine dependence. Adult male Sprague-Dawley rats were trained to self-administer nicotine intravenous. After initial food pellet training, followed by 26 sessions of nicotine self-administration training, the rats were administered noribogaine (12.5, 25 or 50 mg/kg orally), noribogaine vehicle, varenicline or saline using a within-subject design with a Latin square test schedule. Noribogaine dose-dependently decreased nicotine self-administration by up to 64% of saline-treated rats’ levels and was equi-effective to 1.7 mg/kg intraperitoneal varenicline. Noribogaine was less efficient at reducing food pellets self-administration than at nicotine self-administration, inhibiting the nondrug reinforcing effects of palatable pellets by 23% at the highest dose. These results suggest that noribogaine dose-dependently attenuates drug-taking behavior for nicotine, attenuates the reinforcing effects of nicotine and is comparable to varenicline power in that regard. The findings from the present study hold promise for a new therapy to aid smoking cessation.
Food self-administration; α3β4 nicotinic acetylcholine receptor antagonist; α7 nicotinic acetylcholine receptor antagonist; addiction
We have reported that intermediate repeat lengths of the C9ORF72 repeat are a risk factor for Parkinson Disease (PD) in a clinically- diagnosed dataset. As 10-25% of clinically diagnosed PD have different diagnoses upon autopsy, we hypothesized this may reflect phenotypic heterogeneity or concomitant pathology of other neurodegenerative disorders.
We screened 488 autopsy-confirmed PD cases for the expansion haplotype tag, rs3849942T. In 196 identified haplotype carriers, the C9ORF72 repeat was genotyped using the repeat-primed PCR assay.
No larger (intermediate or expanded) repeats were found in these autopsy-confirmed PD samples. This absence of larger repeats is significantly different from the frequency in clinically-diagnosed datasets (p=0.002).
Our results suggest that expanded or intermediate C9ORF72 repeats in clinically-diagnosed PD or Parkinsonism might be an indication of heterogeneity in clinically-diagnosed PD cases. Further studies are needed to elucidate the potential contribution of the C9ORF72 repeat to autopsy-confirmed PD.
autopsy confirmed; Parkinson Disease; C9ORF72 repeat; parkinsonism
Adult-born hippocampal neurons are important for cognitive plasticity in rodents. There is evidence for hippocampal neurogenesis in adult humans, although whether its extent is sufficient to have functional significance has been questioned. We have assessed the generation of hippocampal cells in humans by measuring the concentration of nuclear bomb test-derived 14C in genomic DNA and we present an integrated model of the cell turnover dynamics. We found that a large subpopulation of hippocampal neurons, constituting one third of the neurons, is subject to exchange. In adult humans, 700 new neurons are added per day, corresponding to an annual turnover of 1.75% of the neurons within the renewing fraction, with a modest decline during aging. We conclude that neurons are generated throughout adulthood and that the rates are comparable in middle aged humans and mice, suggesting that adult hippocampal neurogenesis may contribute to human brain function.
Alpha synuclein is increased in dopamine neurons of cocaine abusers and in rats whose alcohol preference is inbred. Recent studies have shown increased alpha-synuclein protein expression in serum of alcoholic patients that is linked with severity of alcohol craving. The aim of this study was to analyze the serum levels of alpha synuclein in healthy subjects and in recently abstinent cocaine abusers. Alpha synuclein protein expression was measured by enzyme-linked immunosorbent assay in serum specimens obtained from 38 recently abstinent cocaine dependent patients and 14 control subjects. The presence of cocaine dependence disorder was based on the Structured Clinical Interview (DSM-IV). Drug severity was assessed by the Addiction Severity Index ratings and composite measures. Scores of the intensity and frequency of cocaine craving episodes were obtained from the Minnesota Cocaine Craving Questionnaire. The serum concentrations of alpha synuclein in cocaine dependent patients were significantly higher as compared with age-matched drug-free controls (p < 0.001). Alpha synuclein levels in blood were significantly correlated with the intensity (r = 0.60, p < 0.001) and frequency (r = 0.64. p < 0.001) of cocaine craving and with thirty days of cocaine use in the prior month before entry to treatment (r = 0.56, p < 0.005). However, there was no correlation between the serum protein levels of alpha synuclein and age in either group. This report is the first demonstration of altered alpha synuclein levels in peripheral blood from cocaine abusers. These data agree with previous reports in postmortem brain of cocaine abusers and provide support for an association between alpha synuclein and cocaine dependence.
Cocaine; serum; dopamine; craving; synuclein
Alzheimer's disease (AD) and related dementias are a major public health challenge and present a therapeutic imperative for which we need additional insight into molecular pathogenesis. We performed a genome-wide association study and analysis of known genetic risk loci for AD dementia using neuropathologic data from 4,914 brain autopsies. Neuropathologic data were used to define clinico-pathologic AD dementia or controls, assess core neuropathologic features of AD (neuritic plaques, NPs; neurofibrillary tangles, NFTs), and evaluate commonly co-morbid neuropathologic changes: cerebral amyloid angiopathy (CAA), Lewy body disease (LBD), hippocampal sclerosis of the elderly (HS), and vascular brain injury (VBI). Genome-wide significance was observed for clinico-pathologic AD dementia, NPs, NFTs, CAA, and LBD with a number of variants in and around the apolipoprotein E gene (APOE). GalNAc transferase 7 (GALNT7), ATP-Binding Cassette, Sub-Family G (WHITE), Member 1 (ABCG1), and an intergenic region on chromosome 9 were associated with NP score; and Potassium Large Conductance Calcium-Activated Channel, Subfamily M, Beta Member 2 (KCNMB2) was strongly associated with HS. Twelve of the 21 non-APOE genetic risk loci for clinically-defined AD dementia were confirmed in our clinico-pathologic sample: CR1, BIN1, CLU, MS4A6A, PICALM, ABCA7, CD33, PTK2B, SORL1, MEF2C, ZCWPW1, and CASS4 with 9 of these 12 loci showing larger odds ratio in the clinico-pathologic sample. Correlation of effect sizes for risk of AD dementia with effect size for NFTs or NPs showed positive correlation, while those for risk of VBI showed a moderate negative correlation. The other co-morbid neuropathologic features showed only nominal association with the known AD loci. Our results discovered new genetic associations with specific neuropathologic features and aligned known genetic risk for AD dementia with specific neuropathologic changes in the largest brain autopsy study of AD and related dementias.
Alzheimer's disease (AD) and related dementias are a major public health challenge and present a therapeutic imperative for which we need additional insight into molecular pathogenesis. We performed a genome-wide association study (GWAS), as well as an analysis of known genetic risk loci for AD dementia, using data from 4,914 brain autopsies. Genome-wide significance was observed for 7 genes and pathologic features of AD and related diseases. Twelve of the 22 genetic risk loci for clinically-defined AD dementia were confirmed in our pathologic sample. Correlation of effect sizes for risk of AD dementia with effect size for hallmark pathologic features of AD were strongly positive and linear. Our study discovered new genetic associations with specific pathologic features and aligned known genetic risk for AD dementia with specific pathologic changes in a large brain autopsy study of AD and related dementias.
Intra-neuronal metabolism of dopamine (DA) begins with production of 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is toxic. According to the ‘catecholaldehyde hypothesis,’ DOPAL destroys nigrostriatal DA terminals and contributes to the profound putamen DA deficiency that characterizes Parkinson’s disease (PD). We tested the feasibility of using post-mortem patterns of putamen tissue catechols to examine contributions of altered activities of the type 2 vesicular monoamine transporter (VMAT2) and aldehyde dehydrogenase (ALDH) to the increased DOPAL levels found in PD. Theoretically, the DA : DOPA concentration ratio indicates vesicular uptake, and the 3,4-dihydroxyphenylacetic acid : DOPAL ratio indicates ALDH activity. We validated these indices in transgenic mice with very low vesicular uptake (VMAT2-Lo) or with knockouts of the genes encoding ALDH1A1 and ALDH2 (ALDH1A1,2 KO), applied these indices in PD putamen, and estimated the percent decreases in vesicular uptake and ALDH activity in PD. VMAT2-Lo mice had markedly decreased DA:DOPA (50 vs. 1377, p < 0.0001), and ALDH1A1,2 KO mice had decreased 3,4-dihydroxyphenylacetic acid:DOPAL (1.0 vs. 11.2, p < 0.0001). In PD putamen, vesicular uptake was estimated to be decreased by 89% and ALDH activity by 70%. Elevated DOPAL levels in PD putamen reflect a combination of decreased vesicular uptake of cytosolic DA and decreased DOPAL detoxification by ALDH.
DOPAC; DOPAL; dopamine; DOPET; monoamine oxidase; Parkinson’s disease
Bisulfite sequencing is the most efficient single nucleotide resolution method for analysis of methylation status at whole genome scale, but improved quality control metrics are needed to better standardize experiments.
We describe BisQC, a step-by-step method for multiplexed bisulfite-converted DNA library construction, pooling, spike-in content, and bioinformatics. We demonstrate technical improvements for library preparation and bioinformatic analyses that can be done in standard laboratories. We find that decoupling amplification of bisulfite converted (bis) DNA from the indexing reaction is an advantage, specifically in reducing total PCR cycle number and pre-selecting high quality bis-libraries. We also introduce a progressive PCR method for optimal library amplification and size-selection. At the sequencing stage, we thoroughly test the benefits of pooling non-bis DNA library with bis-libraries and find that BisSeq libraries can be pooled with a high proportion of non-bis DNA libraries with minimal impact on BisSeq output. For informatics analysis, we propose a series of optimization steps including the utilization of the mitochondrial genome as a QC standard, and we assess the validity of using duplicate reads for coverage statistics.
We demonstrate several quality control checkpoints at the library preparation, pre-sequencing, post-sequencing, and post-alignment stages, which should prove useful in determining sample and processing quality. We also determine that including a significant portion of non-bisulfite converted DNA with bisulfite converted DNA has a minimal impact on usable bisulfite read output.
DNA methylation; Bisulfite sequencing; Bioinformatics
Neuroinflammation plays a critical role in the pathogenesis of Alzheimer’s disease (AD) and involves activation of the innate immune response via recognition of diverse stimuli by pattern recognition receptors (PRRs). The inflammatory inducers and precise innate signaling pathway contributing to AD pathology remain largely undefined.
In the present study we analyzed expression levels of innate immune proteins in temporal and occipital cortices from preclinical (no cognitive impairment, NCI, N = 22) to mild cognitive impairment (MCI, N = 20) associated with AD pathology (N = 20) and AD patients (N = 23). We found that retinoic acid-inducible gene-I (RIG-1) is significantly elevated in the temporal cortex and plasma in patients with MCI. In addition, primary human astrocytes stimulated with the RIG-1 ligand 5′ppp RNA showed increased expression of amyloid precursor protein (APP) and amyloid-β (Aβ), supporting the idea that RIG-1 is involved in the pathology of MCI associated with early progression to AD.
These findings suggest that RIG-1 may play a critical role in incipient AD.
Innate immunity; Rig signaling; RLR; Inflammation; Alzheimer’s disease; Mild cognitive impairment
The accumulation of heteroplasmic mitochondrial DNA (mtDNA) deletions and single nucleotide variants (SNVs) is a well-accepted facet of the biology of aging, yet comprehensive mutation spectra have not been described. To address this, we have used next generation sequencing of mtDNA-enriched libraries (Mito-Seq) to investigate mtDNA mutation spectra of putamen from young and aged donors. Frequencies of the “common” deletion and other “major arc” deletions were significantly increased in the aged cohort with the fold increase in the frequency of the common deletion exceeding that of major arc deletions. SNVs also increased with age with the highest rate of accumulation in the non-coding control region which contains elements necessary for translation and replication. Examination of predicted amino acid changes revealed a skew towards pathogenic SNVs in the coding region driven by mutation bias. Levels of the pathogenic m.3243A>G tRNA mutation were also found to increase with age. Novel multimeric tandem duplications that resemble murine control region multimers and yeast ρ− mtDNAs, were identified in both young and aged specimens. Clonal ∼50 bp deletions in the control region were found at high frequencies in aged specimens. Our results reveal the complex manner in which the mitochondrial genome alters with age and provides a foundation for studies of other tissues and disease states.
Mitochondria are unique among animal organelles in that they contain their own multi-copy genome (mtDNA). For the past 20 years it has been known that tissues like brain and muscle accumulate somatic mtDNA mutations with age. Because individual mtDNA mutations are present at very low levels, few details are known about the spectrum of mutations associated with aging. Advances in sequencing technology now permit the examination of mtDNA mutations at high resolution. We have examined the spectrum of mtDNA mutations present in putamen, a brain region prone to the accumulation of somatic mtDNA mutations. We were able to quantify the accumulation of clonal and non-clonal deletions in the mtDNA coding region which are known to have a strong association with aging. Partial deletions and novel duplications of the mtDNA control region were also identified, and appear to be more prevalent than previously recognized, but levels showed weaker associations with age than coding region deletions. Single nucleotide variants accumulate fastest in the control region, with a skew towards the accumulation of pathogenic mutations in the coding region. Understanding how the mitochondrial genome alters with age provides a benchmark for studies of somatic mtDNA mutations and dissection of the role they play in normal aging and degenerative diseases.
Chronic cocaine use in humans and animal models is known to lead to pronounced alterations in neuronal function in brain regions associated with drug reinforcement. To evaluate whether the alterations in gene expression in cocaine overdose victims are associated with specific dopamine populations in the midbrain, cDNA arrays and western blotting were used to compare gene and protein expression patterns between cocaine overdose victims and age-matched controls in the ventral tegmental area (VTA) and lateral substantia nigra (l-SN). Array analysis revealed significant up-regulation of numerous transcripts in the VTA, but not in the l-SN, of cocaine overdose victims including NMDAR1, GluR2, GluR5 and KA2 receptor mRNA (p < 0.05). No significant alterations between overdose victims and controls were observed for GluR1, R3 or R4 mRNA levels. Correspondingly, western blot analysis revealed VTA-selective up-regulation of CREB (p < 0.01), NMDAR1 (p < 0.01), GluR2 (p < 0.05), GluR5 (p < 0.01) and KA2 (p < 0.05) protein levels of cocaine overdose victims. The present results indicate that selective alterations of CREB and certain ionotropic glutamate receptor (iGluR) subtypes appear to be associated with chronic cocaine use in humans in a region-specific manner. Moreover, as subunit composition determines the functional properties of iGluRs, the observed changes may indicate alterations in the excitability of dopamine transmission underlying long-term biochemical and behavioral effects of cocaine in humans.
cocaine; CREB; gene expression; glutamate; substantia nigra; ventral tegmental area
Chronic cocaine and withdrawal induce significant alterations in nucleus accumbens (NAc) glutamatergic function in humans and rodent models of cocaine addiction. Dysregulation of glutamatergic function of the prefrontal cortical–NAc pathway has been proposed as a critical substrate for unmanageable drug seeking. Previously, we demonstrated significant up-regulation of NMDA, (±)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptor subunit mRNAs and protein levels in the ventral tegmental area (VTA), but not the substantia nigra, of cocaine overdose victims (COD). The present study was undertaken to examine the extent of altered ionotropic glutamate receptor (iGluR) subunit expression in the NAc and the putamen in cocaine overdose victims. Results revealed statistically significant increases in the NAc, but not in the putamen, of NMDA receptor subunit (NR)1 and glutamate receptor subunit (GluR)2/3 wit trends in GluR1 and GluR5 in COD. These results extend our previous finding and indicate pathway-specific alterations in iGluRs in COD. In order to determine that changes were related to cocaine intake and not to other factors in the COD victims, we examined the effects of cocaine intravenous self-administration in rhesus monkeys for 18 months (unit dose of 0.1 mg/kg/injection and daily drug intake of 0.5 mg/kg/session). Total drug intake for the group of four monkeys was 37.9 ± 4.6 mg/kg. Statistically significant elevations were observed for NR1, GluR1, GluR2/3 and GluR5 (p < 0.05) and a trend towards increased NR1 phosphorylated at serine 896 (p = 0.07) in the NAc but not putamen of monkeys self-administering cocaine compared with controls. These results extend previous results by demonstrating an up-regulation of NR1, GluR2/3 and GluR5 in the NAc and suggest these alterations are pathway specific. Furthermore, these changes may mediate persistent drug intake and craving in the human cocaine abuser.
cocaine; glutamate; nucleus accumbens; protein expression; putamen
Most neurodegenerative diseases contain hyperphosphorylated Tau [p-Tau]. We examined for the first time epitopes at which Tau is hyperphosphorylated in Parkinson’s disease, dementia with Lewy bodies and Alzheimer’s disease, and also select Tau kinases.
Postmortem frontal cortex from Parkinson’s disease, dementia with Lewy bodies, Alzheimer’s disease and striata from Parkinson’s disease, were analyzed by immunoblots using commercially available antibodies against 20 different phospho-epitopes of Tau. Major Tau kinases were also screened. Results in diseased tissues were compared to nondiseased controls.
In Alzheimer’s disease, Tau was hyperphosphorylated at all the 20 epitopes of p-Tau. In dementia with Lewy bodies, p-Tau formation occurred at 6 sites sharing 30% overlap with Alzheimer’s disease, while in Parkinson’s frontal cortex, an area which does not degenerate, Tau hyperphosphorylation was seen at just 3 epitopes, indicating 15% overlap with Alzheimer’s disease. In Parkinson’s disease striatum, an area which undergoes considerable neurodegeneration, Tau was hyperphosphorylated at 10 epitopes, sharing 50% overlap with Alzheimer’s disease. Between frontal cortex of Parkinson’s disease and dementia with Lewy bodies, there were only two p-Tau epitopes in common. In striata of Parkinson’s disease, there were 3 clusters of Tau hyperphosphorylated at 3 contiguous sites, while two such clusters were detected in dementia with Lewy bodies; such clusters disrupt axonal transport of mitochondria, cause microtubule remodeling and result in cell death. p-GSK-3β, a major Tau kinase, was activated in all brain regions examined, except in dementia with Lewy bodies. Activation of other Tau kinases was seen in all brain regions, with no clear pattern of activation.
Our studies suggest that the three neurodegenerative diseases each have a signature-specific profile of p-Tau formation which may be useful in understanding the genesis of the diseases and for the development of a panel of specific biomarkers.
Pancreatitis is a complex, progressively destructive inflammatory disorder. Alcohol was long thought to be the primary causative agent, but genetic contributions have been of interest since the discovery that rare PRSS1, CFTR, and SPINK1 variants were associated with pancreatitis risk. We now report two significant genome-wide associations identified and replicated at PRSS1-PRSS2 (1×10-12) and x-linked CLDN2 (p < 1×10-21) through a two-stage genome-wide study (Stage 1, 676 cases and 4507 controls; Stage 2, 910 cases and 4170 controls). The PRSS1 variant affects susceptibility by altering expression of the primary trypsinogen gene. The CLDN2 risk allele is associated with atypical localization of claudin-2 in pancreatic acinar cells. The homozygous (or hemizygous male) CLDN2 genotype confers the greatest risk, and its alleles interact with alcohol consumption to amplify risk. These results could partially explain the high frequency of alcohol-related pancreatitis in men – male hemizygous frequency is 0.26, female homozygote is 0.07.
The study investigates the effects of genetic factors on the pathology of Alzheimer’s disease (AD) and Lewy body (LB) diseases, including Parkinson’s disease and dementia with Lewy bodies. A multicenter autopsy series (762 brain samples) with AD, LB or vascular pathology was examined. We assessed the effects of the tau gene (MAPT) H1 haplotype, the H1-specific SNP rs242557, APOE and the α-synuclein gene (SNCA) 3′UTR SNP rs356165 on the burden of AD and LB pathology. We counted neurofibrillary tangles (NFTs) in four brain regions, senile plaques (SPs) in five and LBs in four. We also documented Braak NFT stage, brain weight and presence of vascular pathology. MAPT H1 associated with lower counts of NFTs in the middle frontal (P<0.001) and inferior parietal (P=0.005) cortices, and also with lower counts of SPs in the motor cortex (P=0.001). Associations of MAPT H1 with increased LB counts in the middle frontal cortex (P=0.011) and inferior parietal cortex (P=0.033) were observed but were not significant after multiple testing adjustment. The APOE ε4 allele was strongly associated with overall Alzheimer type pathology (all P≤0.001). SNCA rs356165 and the MAPT H1-specific SNP rs242557 did not associate with AD or LB pathology. This study shows for the first time that MAPT H1 is associated with reduced Alzheimer type pathology, which could have important implications for the understanding of disease mechanisms and their genetic determinants.
MAPT; SNCA; APOE; Alzheimer pathology; Lewy body
As a model organism in biomedicine, the rhesus macaque (Macaca mulatta) is the most widely used nonhuman primate. Although a draft genome sequence was completed in 2007, there has been no systematic genome-wide comparison of genetic variation of this species to humans. Comparative analysis of functional and nonfunctional diversity in this highly abundant and adaptable non-human primate could inform its use as a model for human biology, and could reveal how variation in population history and size alters patterns and levels of sequence variation in primates.
We sequenced the mRNA transcriptome and H3K4me3-marked DNA regions in hippocampus from 14 humans and 14 rhesus macaques. Using equivalent methodology and sampling spaces, we identified 462,802 macaque SNPs, most of which were novel and disproportionately located in the functionally important genomic regions we had targeted in the sequencing. At least one SNP was identified in each of 16,797 annotated macaque genes. Accuracy of macaque SNP identification was conservatively estimated to be >90%. Comparative analyses using SNPs equivalently identified in the two species revealed that rhesus macaque has approximately three times higher SNP density and average nucleotide diversity as compared to the human. Based on this level of diversity, the effective population size of the rhesus macaque is approximately 80,000 which contrasts with an effective population size of less than 10,000 for humans. Across five categories of genomic regions, intergenic regions had the highest SNP density and average nucleotide diversity and CDS (coding sequences) the lowest, in both humans and macaques. Although there are more coding SNPs (cSNPs) per individual in macaques than in humans, the ratio of dN/dS is significantly lower in the macaque. Furthermore, the number of damaging nonsynonymous cSNPs (have damaging effects on protein functions from PolyPhen-2 prediction) in the macaque is more closely equivalent to that of the human.
This large panel of newly identified macaque SNPs enriched for functionally significant regions considerably expands our knowledge of genetic variation in the rhesus macaque. Comparative analysis reveals that this widespread, highly adaptable species is approximately three times as diverse as the human but more closely equivalent in damaging variation.
Rhesus macaque; Human; Single nucleotide polymorphism; Diversity; Comparative genomics
The dopamine receptor D2 (encoded by DRD2) is implicated in susceptibility to mental disorders and cocaine abuse, but mechanisms responsible for this relationship remain uncertain. DRD2 mRNA exists in two main splice isoforms with distinct functions: D2 long (D2L) and D2 short (D2S, lacking exon 6), expressed mainly postsynaptically and presynaptically, respectively. Two intronic single-nucleotide polymorphisms (SNPs rs2283265 (intron 5) and rs1076560 (intron 6)) in high linkage disequilibrium (LD) with each other have been reported to alter D2S/D2L splicing and several behavioral traits in human subjects, such as memory processing. To assess the role of DRD2 variants in cocaine abuse, we measured levels of D2S and D2L mRNA in human brain autopsy tissues (prefrontal cortex and putamen) obtained from cocaine abusers and controls, and genotyped a panel of DRD2 SNPs (119 abusers and 95 controls). Robust effects of rs2283265 and rs1076560 on reducing formation of D2S relative to D2L were confirmed. The minor alleles of rs2283265/rs1076560 were considerably more frequent in Caucasians (18%) compared with African Americans (7%). Also, in Caucasians, rs2283265/rs1076560 minor alleles were significantly overrepresented in cocaine abusers compared with controls (rs2283265: 25 to 9%, respectively; p=0.001; OR=3.4 (1.7–7.1)). Several SNPs previously implicated in diverse clinical association studies are in high LD with rs2283265/rs1076560 and could have served as surrogate markers. Our results confirm the role of rs2283265/rs1076560 in D2 alternative splicing and support a strong role in susceptibility to cocaine abuse.
alternative splicing; cocaine; dopamine; DRD2; D2S; human; addiction and substance abuse; dopamine; neurogenetics; psychostimulants; drd2; d2s; human; alternative splicing; cocaine
Sharks are among the most threatened groups of marine species. Populations are declining globally to support the growing demand for shark fin soup. Sharks are known to bioaccumulate toxins that may pose health risks to consumers of shark products. The feeding habits of sharks are varied, including fish, mammals, crustaceans and plankton. The cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) has been detected in species of free-living marine cyanobacteria and may bioaccumulate in the marine food web. In this study, we sampled fin clips from seven different species of sharks in South Florida to survey the occurrence of BMAA using HPLC-FD and Triple Quadrupole LC/MS/MS methods. BMAA was detected in the fins of all species examined with concentrations ranging from 144 to 1836 ng/mg wet weight. Since BMAA has been linked to neurodegenerative diseases, these results may have important relevance to human health. We suggest that consumption of shark fins may increase the risk for human exposure to the cyanobacterial neurotoxin BMAA.
β-N-methylamino-L-alanine; neurotoxin; neurodegenerative disease; cyanobacteria; elasmobranch; conservation
By performing identical studies in humans and rats, we attempted to distinguish vulnerability factors for addiction from neurobiological effects of chronic drug exposure. We focused on the GABAergic system within the hippocampus, a brain region that is a constituent of the memory/conditioning neuronal circuitry of addiction that is considered to be important in drug reinforcement behaviors in animals and craving and relapse in humans.
Using RNA-Seq we quantified mRNA transcripts in postmortem total hippocampus from alcoholics, cocaine addicts and controls and also from alcohol-naïve, alcohol preferring (P) and non-preferring (NP) rats selectively bred for extremes of alcohol-seeking behavior that also show a general addictive tendency. A pathway-targeted analysis of 25 GABAergic genes encoding proteins implicated in GABA synthesis, metabolism, synaptic transmission and re-uptake was undertaken.
Directionally consistent and biologically plausible overlapping and specific changes were detected: 14/25 of the human genes and 12/25 of the rat genes showed nominally significant differences in gene expression (global p values: 9×10−14, 7×10−11 respectively). Principal FDR-corrected findings were that GABBR1 was down-regulated in alcoholics, cocaine addicts and P rats with congruent findings in NSF, implicated in GABAB signaling efficacy, potentially resulting in increased synaptic GABA. GABRG2, encoding the gamma2 subunit required for postsynaptic clustering of GABAA receptors together with GPHN, encoding the associated scaffolding protein gephryin, were both down-regulated in alcoholics and cocaine addicts but were both up-regulated in P rats. There were also expression changes specific to cocaine addicts (GAD1, GAD2), alcoholics (GABRA2) and P rats (ABAT, GABRG3).
Our study confirms the involvement of the GABAergic system in alcoholism but also reveals a hippocampal GABA input in cocaine addiction. Congruent findings in human addicts and P rats provide clues to predisposing factors for alcohol and drug addiction. Finally, the results of this study have therapeutic implications.