Biology subjects

Dion, P. A.

Publications and source records attributed to Dion, P. A..

5 recordsLinked to original sources

bioRxiv2019

Multi-tissue probabilistic fine-mapping of transcriptome-wide association study identifies cis-regulated genes for miserableness

Miserableness is a behavioural trait that is characterized by strong negative feelings in an individual. Although environmental factors tend to invoke miserableness, it is common to feel miserable for no reason, suggesting an innate, potential genetic component. Currently, little is known about the functional relevance of common variants associated with miserableness. To further characterize the trait, we conducted a transcriptome-wide association study (TWAS) on 373,733 individuals and identified 104 signals across brain tissue panels with 37 unique genes. Subsequent probabilistic fine-mapping prioritized 95 genes into 90%-credible sets. Amongst these prioritized hits, C7orf50 had the highest posterior inclusion probability of 0.869 in the brain cortex. Furthermore, we demonstrate that many GWAS hits for miserableness are driven by expression. To conclude, we successfully identified several genes implicated in miserableness and highlighted the power of TWAS to prioritize genes associated with a trait.\n\nShort summaryThe first transcriptome-wide association study of miserableness identifies many genes including c7orf50 implicated in the trait.

genetics↗

bioRxiv2019

Investigation of the pathogenic RFC1 repeat expansion in a Canadian and a Brazilian ataxia cohort: identification of novel conformations

A homozygous pentanucleotide expansion in the RFC1 gene has been shown to be a common cause of late-onset ataxia. In the general population a total of four different repeat conformations have been observed: a wild type sequence AAAAG (11 repeats), and longer expansions of AAAAG, AAAGG and AAGGG sequences. However, in ataxia cases only the AAGGG expansion has been shown to be pathogenic. In this study, we assessed the prevalence and nature of RFC1 repeat expansions in three adult-onset ataxia cohorts: Brazilian (n = 23) and Canadian (n = 26) cases that tested negative for other known ataxia mutations, as well as a cohort of randomly selected Canadian cases (n = 128) without regard to a genetic diagnosis. We identified the homozygous AAGGG pathogenic expansion in only one Brazilian family with two affected siblings, and in one Canadian case. The RFC1 expansion may therefore not be a common cause of adult-onset ataxia in these populations. Interestingly we observed two new repeat motifs, AAGAG and AGAGG, which indicates the dynamic nature of the pentanucleotide expansion sequence. To assess the frequency of these two new repeat conformations in the general population we screened 163 healthy individuals. These novel motifs were more frequent in patients versus controls. While we cannot be certain that the homozygous genotypes of the novel expanded conformations are pathogenic, their occurrence should nonetheless be taken into consideration in future studies.

genetics↗

bioRxiv2019

Multi-omics integration of the phenome, transcriptome and genome highlights genes and pathways relevant to essential tremor

The genetic factors predisposing to essential tremor (ET), of one of the most common movement disorders, remains largely unknown. While current studies have examined the contribution of both common and rare genetic variants, very few have investigated the ET transcriptome. To understand pathways and genes relevant to ET, we used an RNA sequencing approach to interrogate the transcriptome of two cerebellar regions, the dentate nucleus and cerebellar cortex, in 16 cases and 16 age- and sex-matched controls. Additionally, a phenome-wide association study (pheWAS) of the dysregulated genes was conducted, and a genome-wide gene association study (GWGAS) was done to identify pathways overlapping with the transcriptomic data. We identified several novel dysregulated genes including CACNA1A, a calcium voltage-gated channel implicated in ataxia. Furthermore, several pathways including axon guidance, olfactory loss, and calcium channel activity were significantly enriched. A subsequent examination of the ET GWGAS data (N=7,154) also flagged genes involved in calcium ion-regulated exocytosis of neurotransmitters to be significantly enriched. Interestingly, the pheWAS identified that the dysregulated gene, SHF, is associated with a blood pressure medication (P=9.3E-08), which is commonly used to reduce tremor in ET patients. Lastly, it is also notable that the dentate nucleus and cerebellar cortex have different transcriptomes, suggesting that different regions of the cerebellum have spatially different transcriptomes.

genomics↗

bioRxiv2019

Genome-wide estimates of heritability and genetic correlations in Essential Tremor

Despite considerable efforts to identify disease-causing and risk factors contributing to essential tremor (ET), no comprehensive assessment of heritable risk has been performed to date. We use GREML-LDMS to estimate narrow-sense heritability due to additive effects (h2) and GREMLd to calculate non-additive heritability due to dominance variance ({delta}2) using data from 1,748 ET cases and 5,302 controls. We evaluate heritability per 10Mb segments across the genome and assess the impact of Parkinsons disease (PD) misdiagnosis on heritability estimates. We apply genetic risk score (GRS) from PD and restless legs syndrome (RLS) to explore its contribution to ET risk and further assess genetic correlations with 832 traits by Linkage disequilibrium score regression. Our results show for the first time that ET is a highly heritable condition (h2=0.755, s.e=0.075) in which additive common variability plays a prominent role. In contrast, dominance variance shows insignificant effect on the overall estimates. Heritability split by 10Mb regions revealed increased estimates at chromosomes 6 and 21 suggesting that these may contain causative risk variants influencing susceptibility to ET. The proportion of genetic variance due to PD misdiagnosed cases was estimated to be 5.33%. PD and RLS GRS were not significantly predictive of ET case-control status demonstrating that despite overlapping symptomatology, ET does not seem to share genetic etiologies with PD or RLS. Our study suggests that most of ET genetic component is yet to be discovered and future GWAS will reveal additional risk factors that will improve our understanding of this disabling disorder.

genetics↗

bioRxiv2019

Transcriptomic changes resulting from STK32B overexpression identifies pathways potentially relevant to essential tremor

Essential tremor (ET) is a common movement disorder that has a high heritability. A number of genetic studies have associated different genes and loci with ET, but few have investigated the biology of any of these genes. STK32B was significantly associated with ET in a large GWAS study and was found to be overexpressed in ET cerebellar tissue. Here, we overexpressed STK32B in human cerebellar DAOY cells and used an RNA-Seq approach to identify differentially expressed genes by comparing the transcriptome profile of these cells to the one of control DAOY cells. Pathway and gene ontology enrichment identified axon guidance, olfactory signalling and calcium-voltage channels as significant. Additionally, we show that overexpressing STK32B affects transcript levels of previously implicated ET genes such as FUS. Our results investigate the effects of overexpressed STK32B and suggest that it may be involved in relevant ET pathways and genes.

genomics↗