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Analysis of DNM3 and VAMP4 as genetic modifiers of LRRK2 Parkinsons disease

ObjectiveTo assess genetic modifiers of Parkinsons disease (PD) age at onset (AAO) penetrance in individuals carrying common and rare LRRK2 risk alleles\n\nMethodsWe analysed reported genetic modifier DNM3 rs2421947 in 724 LRRK2 p.G2019S heterozygotes using linear regression of AAO. We meta-analysed our data with previously published data (n=754). VAMP4 is in close proximity to DNM3 and is associated with PD. We analysed the effect of the rs11578699 VAMP4 variant on pG2019S penetrance in 786 LRRK2 p.G2019S heterozygotes. We also evaluated the impact of VAMP4 variants using AAO regression in 4882 patients with PD carrying a common LRRK2 risk variant (rs10878226).\n\nResultsThere was no evidence for linkage disequilibrium between DNM3 rs2421947 and VAMP4 rs11578699. Our linear regression AAO of 724 p.G2019S carriers showed no relationship between DNM3 rs2421947 and AAO (beta = -1.19, p = 0.55, n =708). Meta-analysis with previously published data did not indicate a significant effect on AAO (beta = -2.21, p = 0.083, n = 1304), but there was significant heterogeneity in the analyses of new and previously published data. VAMP4 rs11578699 was nominally associated with AAO in patients dichotomized by the common LRRK2 risk variant rs10878226 (beta=1.68, se=0.81 p=0.037).\n\nInterpretationAnalysis of DNM3 in previously unpublished data does not show an interaction between DNM3 and LRRK2 G2019S for AAO, however the inter-study heterogeneity may indicate ethnic-specific effects of DNM3 rs2421947. Analysis of sporadic PD patients stratified by the PD risk variant rs10878226 indicates a possible interaction between LRRK2 and VAMP4.

genetics

Genetic analysis of the STIM1 gene in chronic pancreatitis

Chronic pancreatitis is a complex disease that involves many factors, both genetic and environmental. Over the past two decades, molecular genetic analysis of five genes that are highly expressed in human pancreatic acinar cells, namely PRSS1, PRSS2, SPINK1, CTRC and CTRB1/CTRB2, has established that a trypsin-dependent pathway plays a key role in the etiology of chronic pancreatitis. Since Ca2+ deregulation can lead to intracellular trypsin activation in experimental acute pancreatitis, we analyzed STIM1 (encoding stromal interaction molecule-1, the main regulator of Ca2+ homeostasis in pancreatic acinar cells) as a candidate modifier gene in French, German and Chinese patients with chronic pancreatitis. The French and German subjects were analyzed by Sanger sequencing whereas the Chinese subjects were analyzed by targeted next-generation sequencing confirmed by Sanger sequencing. A total of 37 rare coding variants (35 missense and 2 nonsense) were identified, which were enriched in patients as compared with controls [2.28% (47/2,057) vs. 0.99% (33/3,322); odds ratio = 2.33, P = 0.0001]. This is the first large case-control study to demonstrate a putative association of rare STIM1 coding variants with chronic pancreatitis. Functional analysis will be required to clarify whether or not the rare STIM1 variants detected predispose to pancreatitis.

genetics

Bidirectional Mendelian randomization analysis of shared genetic signals between coexisting neurodegenerative disorders to decipher underlying causal pathways

OBJECTIVETo investigate whether coexistence of various neurodegenerative disorders is coincidental or biologically connected.\n\nDESIGNTwo sample Mendelian randomization using summary effect estimates\n\nSETTINGGenetic data taken on various neurodegenerative disorders from various cohorts comprising individuals predominantly of European ancestry.\n\nPARTICIPANTSInternational Genomics of Alzheimers patients (IGAP), project MinE, International Age-related Macular Degeneration Consortium (IAMDGC), International Multiple Sclerosis Genetics Consortium (IMSGC), International Parkinsons Disease Genomics Consortium (IPDGC)\n\nMAIN OUTCOME MEASURESAlzheimers disease (AD), Amyotrophic lateral sclerosis (ALS), Age related macular degeneration (AMD), Multiple sclerosis (MS) and Parkinsons disease (PD).\n\nRESULTSA Bonferroni corrected threshold of P=0.005 was considered to be significant, and P<0.05 was considered suggestive of evidence for a potential association. I observed a risky effect of PD on ALS (OR = 1.126, 95% CI = 1.059-1.198, P = 0.005). Using AD as exposure and PD as outcome, I observed a risky effect of AD on PD using all the MR methods with strongest results using MBE method (OR = 2.072, 95% CI = 1.006-4.028, P = 0.0416). Genetic predisposition to AD was further observed to be a risky for AMD (OR = 1.759, 95% CI = 1.040-1.974, P = 0.0363). On the contrary, AMD was observed to be strongly protective towards MS (OR = 0.861, 95% CI = 0.776-0.955, P = 0.0059).\n\nCONCLUSIONSMy findings are consistent with the previously observed relative occurrence of co-existing neurodegenerative diseases or overlapping symptoms among neurodegenerative diseases.

genetics

A genetic screen for genes that impact peroxisomes in Drosophila identifies candidate genes for human disease

Peroxisomes are sub-cellular organelles that are essential for proper function of eukaryotic cells. In addition to being the sites of a variety of oxidative reactions, they are crucial regulators of lipid metabolism. Peroxisome loss or dysfunction leads to multisystem diseases in humans that strongly affects the nervous system. In order to uncover previously unidentified genes and mechanisms that impact peroxisomes, we conducted a genetic screen on a collection of lethal mutations on the X chromosome in Drosophila. Using the number, size and morphology of GFP tagged peroxisomes as a readout, we screened for mutations that altered the number and morphology of peroxisomes based on clonal analysis and confocal microscopy. From this screen, we identified 18 genes that cause increases in peroxisome number or altered morphology when mutated. We examined the human homologs of these genes and found that they are involved in a diverse array of cellular processes. Interestingly, the human homologs from the X-chromosome collection are under selective constraint in human populations and are good candidate genes particularly for dominant genetic disease. This in vivo screening approach for peroxisome defects allows identification of novel genes that impact peroxisomes in vivo in a multicellular organism and is a valuable platform to discover genes potentially involved in dominant disease that could affect peroxisomes.

genetics

Carotid intima-media thickness in UK Biobank: Identification of novel genome-wide loci, sex-specific effects and genetic correlations with obesity and glucometabolic traits.

ObjectivesAtherosclerosis is the underlying cause of most cardiovascular disease, but mechanisms underlying atherosclerosis are incompletely understood. Ultra-sound measurement of the carotid artery intima-media thickness (cIMT) can be used to measure vascular remodelling, which is indicative of atherosclerosis. Genome-wide association studies have identified a number of genetic loci associated with cIMT, but heterogeneity of measurements collected by many small cohorts have been a major limitation in these efforts. Here we conducted genome-wide association analyses in UK Biobank (N=22,179), the largest single study with consistent cIMT measurements.\n\nApproach and resultsWe used BOLT-LMM to run linear regression of cIMT in UK Biobank, adjusted for age, sex, genotyping platform and population structure. In white British participants, we identified 4 novel loci associated with cIMT and replicated most previously reported loci. In the first sex-specific analyses of cIMT, we identified a female-specific locus on Chromosome 5, associated with cIMT in women only and highlight VCAN as a good candidate gene at this locus. Genetic correlations with body-mass index and glucometabolic traits were also observed.\n\nConclusionThese findings replicate previously reported associations, highlight novel biology and provide new directions for investigating the sex differences observed in cardiovascular disease presentation and progression.

genetics

High-density genetic linkage map construction and white rot resistance QTL mapping for Vitis based on restriction site-associated DNA sequencing

Grape white rot (Coniothyrium diplodiella) is a major fungal disease affecting grape yield and quality. The present study aimed to provide a foundation to improve future grape white rot resistance breeding. To this end, interspecific hybridization was conducted between a white rot resistance cultivar Zhuosexiang (Vitus vinifera L. x Vitus labrusca L.), and a susceptible cultivar Victoria (Vitus vinifera L.), using 177 hybrid offspring and two parents for restriction site-associated DNA sequencing (RAD-seq) and high-density genetic linkage mapping. Female, male, and integrated map marker numbers were 2501, 4110, and 6249, respectively. The average genetic distance of adjacent markers was 1.25 cM, 0.77 cM, and 0.50 cM. White rot resistance identification of the two parents and 177 individuals was conducted in July and August of 2017 and 2018. Additionally, white rot resistance quantitative trait locus (QTL) mapping was conducted. In total, nine QTLs were detected and located on linkage groups LG1, LG4, LG7, LG12, LG14, and LG15, with overlapping QTLs on LG7 and LG15. Further, three candidate genes that may be responsible for grape white rot resistance were screened. The results will provide an important theoretical reference for future grape white rot resistance breeding.

genetics

Assignment of frost tolerant coast redwood trees of unknown origin to populations within their natural range using nuclear and chloroplast microsatellite genetic markers

Considering climate change and expected changes in temperature and precipitation, some introduced timber species are prospective for growing in Germany or Europe to produce valuable wood products and support sustainable forestry. The Californian tree, coast redwood (Sequoia sempervirens [D. Don] Endl.) is one of such species due to its excellent wood properties and high growth rate. It is sensitive to the freezing temperatures, but several trees of unknown origin introduced to Germany decades ago demonstrated high frost tolerance, and their propagated cuttings were planted all over German botanic gardens and arboreta. The knowledge of their origin within the natural distribution range could help us identify the potential genetic resources of frost resistant coast redwood genotypes. Therefore, both trees of unknown origin in Germany (G) and two reference data sets representing the \"Kuser provenance test\" established in 1990 in France (F) and samples collected in California (C) with known origin were genotyped using 18 microsatellite markers including 12 nuclear and six chloroplast simple sequence repeat (cpSSR) markers. The number of haplotypes found in the data sets based on six cpSSR markers was surprisingly very high. These markers were used to assign the German frost resistant trees (G) to the two reference data sets (F and C). The genetic structure among California samples (C) based on nSSR and cpSSR markers was very weak and mainly due to northern and southern clusters separated by the San Francisco Bay as a geographic barrier between coast redwood populations confirming previously published data. It was impossible to confidently assign frost tolerant trees (G) to single native populations, but rather to either the northern or southern cluster. However, the existing frost tolerant genotypes can already be used to establish commercial coast redwood plantation for future German forestry.

genetics

The Impact of Genetic Background and Cell Lineage on the Level and Pattern of Position Effect Variegation

BackgroundChromatin-based transcriptional silencing is often described as a stochastic process, largely because of the mosaic expression observed in position effect variegation (PEV), where a euchromatic reporter gene is juxtaposed with heterochromatin. Here we closely examine the impact of genetic background on PEV phenotypes in the fruit fly, Drosophila melanogaster.\n\nResultsUsing consecutive generations of selective breeding, we isolated, from a single laboratory population, two inbred lines exhibiting contrasting degrees of variegation (A1: low expression, D1: high expression). Within each inbred population, remarkable similarity is observed in both the degree and the pattern of variegation. 89.63% of the differences between the two inbred lines in the degree of silencing can be explained by genotype, while a modest but significant sex effect is also observed. Further analyses of the PEV phenotype in the progeny of crosses between A1 and D1 suggest that the genotypic effect is the result of the combined effect of multiple independent trans-acting loci. While the initial observations are based on a PEV phenotype scored in the fly eye (hsp70-white reporter), similar degrees of silencing were observed using a beta-gal reporter that can be scored across the whole fly. The pattern of variegating hsp70-white expression among individual flies becomes almost identical after five generations of inbreeding. Using a reporter inserted into the heterochromatic fourth chromosome, image analysis found significant enrichment of pigmentation in the ventral-posterior quadrant in both the A1 and D1 lines, and in the F1 and F2 progeny produced from a cross between A1 and D1, despite different degrees of expression.\n\nConclusionsCombining these results with the spreading model for local heterochromatin formation, we propose an augmented stochastic model to describe PEV. In this model, the genetic background, which determines the overall level of silencing, works with the cell lineage specific regulatory environment to determine the on/ off probability at the reporter locus in each cell. This model acknowledges cell-type specific events, as well as the general impact of heterochromatin formation.

genetics

Large-scale Genetic Analysis Identifies 66 Novel Loci for Asthma

We carried out a genome-wide association study (GWAS) for asthma in UK Biobank, followed by a meta-analysis with results from the Trans-National Asthma Genetic Consortium (TAGC). 66 novel genomic regions were identified, bringing the number of known asthma susceptibility loci to 211. Significant gene-sex interactions were also observed where susceptibility alleles, either individually or as a function of polygenic risk scores, increased asthma risk to a greater extent in men than women. Bioinformatics analyses demonstrated that asthma-associated variants were enriched for colocalizing to regions of open chromatic in immune cells and identified candidate causal genes at 52 of the novel loci, including CD52. An anti-CD52 (-CD52) antibody mimicked the immune cell-depleting effects of an FDA-approved human -CD52 antibody and reduced allergen-induced airway hyperreactivity in mice. These results further elucidate the genetic architecture of asthma, provide evidence that the immune system plays a prominent role in its pathogenesis, and suggest that CD52 represents a potentially novel therapeutic target for treating asthma.

genetics

A genome-wide genetic pleiotropy approach identified shared loci between multiple system atrophy and inflammatory bowel disease

We aimed to identify shared genetic background between multiple system atrophy (MSA) and autoimmune diseases by using the conjFDR approach. Our study showed significant genetic overlap between MSA and inflammatory bowel disease and identified DENND1B, C7, and RSP04 loci, which are linked to significant changes in methylation or expression levels of adjacent genes. We obtained evidence of enriched heritability involving immune/digestive categories. Finally, an MSA mouse model showed dysregulation of the C7 gene in the degenerating midbrain compared to wildtype mice. The results identify novel molecular mechanisms and implicate immune and gut dysfunction in MSA pathophysiology.

genetics

Distinguishing pedigree relationships using multi-way identical by descent sharing and sex-specific genetic maps

The proportion of samples with one or more close relatives in a genetic dataset increases rapidly with sample size, necessitating relatedness modeling and enabling pedigree-based analyses. Despite this, relatives are generally unreported and current inference methods typically detect only the degree of relatedness of sample pairs and not pedigree relationships. We developed CREST, an accurate and fast method that identifies the pedigree relationships of close relatives. CREST utilizes identical by descent (IBD) segments shared between a pair of samples and their mutual relatives, leveraging the fact that sharing rates among these individuals differ across pedigree configurations. Furthermore, CREST exploits the profound differences in sex-specific genetic maps to classify pairs as maternally or paternally related--e.g., paternal half-siblings--using the locations of autosomal IBD segments shared between the pair. In simulated data, CREST correctly classifies 91.5-99.5% of grandparent-grandchild (GP) pairs, 70.5-97.0% of avuncular (AV) pairs, and 79.0-98.0% of half-siblings (HS) pairs compared to PADREs rates of 38.5-76.0% of GP, 60.5-92.0% of AV, 73.0-95.0% of HS pairs. Turning to the real 20,032 sample Generation Scotland (GS) dataset, CREST correctly determines the relationship of 99.0% of GP, 85.7% of AV, and 95.0% of HS pairs that have sufficient mutual relative data, completing this analysis in 10.1 CPU hours including IBD detection. CRESTs maternal and paternal relationship inference is also accurate, as it flagged five pairs as incorrectly labeled in the GS pedigrees-- three of which we confirmed as mistakes, and two with an uncertain relationship--yielding 99.7% of HS and 93.5% of GP pairs correctly classified.

genetics

Shared regulatory pathways reveal novel genetic correlations between grip strength and neuromuscular disorders

BackgroundMuscle weakness and muscle wasting can be a consequence of aging (sarcopenia) and neuromuscular disorders (NMD). Genome-wide association (GWA) studies have identified genetic variants associated with grip strength (GS, an inverse measure of muscle weakness) and NMD (multiple sclerosis (MS), myasthenia gravis (MG) and amyotrophic lateral sclerosis (ALS)). However, how these variants contribute to the muscle weakness caused by aging or NMD remains obscure.\n\nMethodsWe have integrated GS and NMD associated SNPs in a multimorbid analysis that leverages high-throughput chromatin interaction (Hi-C) data and expression quantitative trait loci (eQTL) data to identify allele-specific gene regulation (i.e. eGenes). Pathways and shared drug targets that are enriched by colocalised eGenes were then identified using pathway and drug enrichment analysis.\n\nResultsWe identified gene regulatory mechanisms (eQTL-eGene effects) associated with GS, MG, MS and ALS. The eQTLs associated with GS regulate a subset of eGenes that are also regulated by the eQTLs of MS, MG and ALS. Yet, we did not find any eGenes commonly regulated by all four phenotypes associated eQTLs. By contrast, we identified three pathways (mTOR signaling, axon guidance, and alcoholism) that are commonly affected by the gene regulatory mechanisms associated with all four phenotypes. 13% of the eGenes we identified were known drug targets, and GS shares at least one druggable eGene and pathway with each of the NMD phenotypes.\n\nConclusionsCollectively, these findings identify significant biological overlaps between GS and NMD, demonstrating the potential for spatial genetic analysis to identify mechanisms underlying muscle weakness due to aging and NMD.

genetics

WormQTL2: an interactive platform for systems genetics in Caenorhabditis elegans

Quantitative genetics provides the tools for linking polymorphic loci (QTLs) to trait variation. Linkage analysis of gene expression is an established and widely applied method, leading to the identification of expression quantitative trait loci (eQTLs). (e)QTL detection facilitates the identification and understanding of the underlying molecular components and pathways, yet (e)QTL data access and mining often is a bottleneck. Here we present WormQTL2 (www.bioinformatics.nl/WormQTL2/), a database and platform for comparative investigations and meta-analyses of published (e)QTL datasets in the model nematode worm C. elegans. WormQTL2 integrates six eQTL studies spanning 11 conditions as-well-as over 1000 traits from 32 studies and allows experimental results to be compared, reused, and extended upon to guide further experiments and conduct systems-genetic analyses. For example, one can easily screen a locus for specific cis-eQTLs that could be linked to variation in other traits, detect gene-by-environment interactions by comparing eQTLs under different conditions, or find correlations between QTL profiles of classical traits and gene expression.

genetics

Future Preventive Gene Therapy of Polygenic Diseases from a Population Genetics Perspective

With the accumulation of scientific knowledge of the genetic causes of common diseases and continuous advancement of gene-editing technologies, gene therapies to prevent polygenic diseases may soon become possible. This study endeavored to assess population genetics consequences of such therapies. Computer simulations were used to evaluate the heterogeneity in causal alleles for polygenic diseases that could exist among geographically distinct populations. The results show that although heterogeneity would not be easily detectable by epidemiological studies following population admixture, even significant heterogeneity would not impede the outcomes of preventive gene therapies. Preventive gene therapies designed to correct causal alleles to a naturally-occurring neutral state of nucleotides would lower the prevalence of polygenic early- to middle-age-onset diseases in proportion to the decreased population relative risk attributable to the edited alleles. The outcome would manifest differently for late-onset diseases, for which the therapies would result in a delayed disease onset and decreased lifetime risk, however the lifetime risk would increase again with prolonging population life expectancy, which is a likely consequence of such therapies. If gene therapies that prevent heritable diseases were to be applied on a large scale, the decreasing frequency of risk alleles in populations would reduce the disease risk or delay the age of onset, even with a fraction of the population receiving such therapies. With ongoing population admixture, all groups would benefit over generations.

genetics

No genetic evidence for involvement of alcohol dehydrogenase genes in risk for Parkinson’s disease

Multiple genes have been implicated in Parkinsons disease (PD), including causal gene variants and risk variants typically identified using genome-wide association studies (GWAS). Variants in the alcohol dehydrogenase genes ADH1C and ADH1B are among the genes that have been associated with PD, suggesting that this family of genes may be important in PD. As part of the International Parkinsons Disease Genomics Consortiums (IPDGC) efforts to scrutinize previously reported risk factors for PD, we explored genetic variation in the alcohol dehydrogenase genes ADH1A, ADH1B, ADH1C, ADH4, ADH5, ADH6, and ADH7 using imputed GWAS data from 15,097 cases and 17,337 healthy controls. Rare-variant association tests and single-variant score tests did not show any statistically significant association of alcohol dehydrogenase genetic variation with the risk for PD.

genetics

Cell-to-cell expression dispersion of B-cell surface proteins displays genetic variation among humans

Variability in gene expression across a population of homogeneous cells is known to influence various biological processes. In model organisms, natural genetic variants were found that modify expression dispersion (variability at a fixed mean) but whether such effects exist in humans has not been fully demonstrated. Here, we analyzed single-cell expression of four proteins (CD23, CD55, CD63 and CD86) across cell lines derived from individuals of the Yoruba population. Using data from over 30 million cells, we found substantial inter-individual variation of dispersion. We demonstrate, via de novo cell line generation and subcloning experiments, that this variation exceeds the variation associated with cellular immortalization. By association mapping, we linked the expression dispersion of CD63 to the rs971 SNP. Our results show that human DNA variants can have inherently-probabilistic effects on gene expression. Such subtle genetic effects may participate to phenotypic variation and disease predisposition.

genetics

Integration of Multi-level Molecular Scoring for the Interpretation of RAS-Family Genetic Variation

Protein-coding genetic variants are the first considered in most studies and Precision Medicine workflows, but their interpretation is primarily driven by DNA sequence-based analytical tools and annotations. Thus, more specific and mechanistic interpretations should be attainable by integrating DNA-based scores with scores from the protein 3D structure. However, reliable and reproducible standardization of methods that use 3D structure for genomic variation is still lacking. Further, we believe that the current paradigm of aiming to directly predict the pathogenicity of variants skips the critical step of inferring, with precision, molecular mechanisms of dysfunction. Thus, we report herein the development and evaluation of single and composite 3D structure-based scores and their integration with protein and DNA sequence-based scores to better understand not only if a genomic variant alters a protein, but how. We believe this is a critical step for understanding mechanistic changes due to genomic variants, designing functional validation tests, and for improving disease classifications. We applied this approach to the RAS gene family encoding seven distinct proteins and their 935 unique missense variants present somatically in cancer, in rare diseases (termed RASopathies), and in the currently healthy adult population. This knowledge shows that protein structure-based scores are distinct from information available from genomic annotation, that they are useful for interpreting genomic variants, and they should be taken into consideration in future guidelines for genomic data interpretation.\n\nSignificance StatementGenetic information from patients is a powerful data type for understanding individual differences in disease risk and treatment, but most of the genetic variation we observe has no mechanistic interpretation. This lack of interpretation limits the use of genomics data in clinical care. Standard methods for genomics data interpretation take advantage of annotations available for the human reference genome, but they do not consider the 3D protein molecule. We believe that changes to the 3D molecule must be considered, to augment current practice and lead to more precise interpretation. In this work, we present our initial process for systematic multi-level molecular scores, including 3D, to interrogate 935 RAS-family variants that are relevant in both cancer and rare diseases.

genetics

Loss of UGP2 in brain leads to a severe epileptic encephalopathy, emphasizing that bi-allelic isoform specific start-loss mutations of essential genes can cause genetic diseases

Developmental and/or epileptic encephalopathies (DEEs) are a group of devastating genetic disorders, resulting in early onset, therapy resistant seizures and developmental delay. Here we report on 12 individuals from 10 families presenting with a severe form of intractable epilepsy, severe developmental delay, progressive microcephaly and visual disturbance. Whole exome sequencing identified a recurrent, homozygous variant (chr2:64083454A>G) in the essential UDP-glucose pyrophosphorylase (UGP2) gene in all probands. This rare variant results in a tolerable Met12Val missense change of the longer UGP2 protein isoform but causes a disruption of the start codon of the shorter isoform. We show that the absence of the shorter isoform leads to a reduction of functional UGP2 enzyme in brain cell types, leading to altered glycogen metabolism, upregulated unfolded protein response and premature neuronal differentiation, as modelled during pluripotent stem cell differentiation in vitro. In contrast, the complete lack of all UGP2 isoforms leads to differentiation defects in multiple lineages in human cells. Reduced expression of Ugp2a/Ugp2b in vivo in zebrafish mimics visual disturbance and mutant animals show a behavioral phenotype. Our study identifies a recurrent start codon mutation in UGP2 as a cause of a novel autosomal recessive DEE. Importantly, it also shows that isoform specific start-loss mutations causing expression loss of a tissue relevant isoform of an essential protein can cause a genetic disease, even when an organism-wide protein absence is incompatible with life. We provide additional examples where a similar disease mechanism applies.

genetics