SLC6A1 variant pathogenicity, molecular function, and phenotype: a genetic and clinical analysis

in Brain: a Journal of Neurology (2023)

Genetic variants in the SLC6A1 gene can cause a broad phenotypic disease spectrum by altering the protein function. Thus, systematically curated clinically relevant genotype-phenotype associations are ... [more ▼]

Genetic variants in the SLC6A1 gene can cause a broad phenotypic disease spectrum by altering the protein function. Thus, systematically curated clinically relevant genotype-phenotype associations are needed to understand the disease mechanism and improve therapeutic decision-making. We aggregated genetic and clinical data from 172 individuals with likely pathogenic/pathogenic (lp/p) SLC6A1 variants and functional data for 184 variants (14.1% lp/p). Clinical and functional data were available for a subset of 126 individuals. We explored the potential associations of variant positions on the GAT1 3D structure with variant pathogenicity, altered molecular function, and phenotype severity using bioinformatic approaches. The GAT1 transmembrane domains 1, 6, and extracellular loop 4 (EL4) were enriched for patient over population variants. Across functionally tested missense variants (n = 156), the spatial proximity from the ligand was associated with loss-of-function in the GAT1 transporter activity. For variants with complete loss of in vitro GABA uptake, we found a 4.6-fold enrichment in patients having severe disease vs. non-severe disease (P = 2.9e-3, 95% CI: 1.5 - 15.3). In summary, we delineated associations between the 3D structure and variant pathogenicity, variant function, and phenotype in SLC6A1-related disorders. This knowledge supports biology-informed variant interpretation and research on GAT1 function. All our data can be interactively explored in the SLC6A1 Portal (https://slc6a1-portal.broadinstitute.org/). [less ▲]

GWAS meta-analysis of over 29,000 people with epilepsy identifies 26 risk loci and subtype-specific genetic architecture

in Nature Genetics (2023)

Epilepsy is a highly heritable disorder affecting over 50 million people worldwide, of which about one-third are resistant to current treatments. Here we report a multi-ancestry genome-wide association ... [more ▼]

Epilepsy is a highly heritable disorder affecting over 50 million people worldwide, of which about one-third are resistant to current treatments. Here we report a multi-ancestry genome-wide association study including 29,944 cases, stratified into three broad categories and seven subtypes of epilepsy, and 52,538 controls. We identify 26 genome-wide significant loci, 19 of which are specific to genetic generalized epilepsy (GGE). We implicate 29 likely causal genes underlying these 26 loci. SNP-based heritability analyses show that common variants explain between 39.6 and 90 of genetic risk for GGE and its subtypes. Subtype analysis revealed markedly different genetic architectures between focal and generalized epilepsies. Gene-set analyses of GGE signals implicate synaptic processes in both excitatory and inhibitory neurons in the brain. Prioritized candidate genes overlap with monogenic epilepsy genes and with targets of current antiseizure medications. Finally, we leverage our results to identify alternate drugs with predicted efficacy if repurposed for epilepsy treatment. [less ▲]

Spatio-functional organization in virocells of small uncultivated archaea from the deep biosphere.

in ISME Journal (2023)

Despite important ecological roles posited for virocells (i.e., cells infected with viruses), studying individual cells in situ is technically challenging. We introduce here a novel correlative ... [more ▼]

Despite important ecological roles posited for virocells (i.e., cells infected with viruses), studying individual cells in situ is technically challenging. We introduce here a novel correlative microscopic approach to study the ecophysiology of virocells. By conducting concerted virusFISH, 16S rRNA FISH, and scanning electron microscopy interrogations of uncultivated archaea, we linked morphologies of various altiarchaeal cells to corresponding phylogenetic signals and indigenous virus infections. While uninfected cells exhibited moderate separation between fluorescence signals of ribosomes and DNA, virocells displayed complete cellular segregation of chromosomal DNA from viral DNA, the latter co-localizing with host ribosome signals. A similar spatial separation was observed in dividing cells, with viral signals congregating near ribosomes at the septum. These observations suggest that replication of these uncultivated viruses occurs alongside host ribosomes, which are used to generate the required proteins for virion assembly. Heavily infected cells sometimes displayed virus-like particles attached to their surface, which agree with virus structures in cells observed via transmission electron microscopy. Consequently, this approach is the first to link genomes of uncultivated viruses to their respective structures and host cells. Our findings shed new light on the complex ecophysiology of archaeal virocells in deep subsurface biofilms and provide a solid framework for future in situ studies of virocells. [less ▲]

HLA in isolated REM sleep behavior disorder and Lewy body dementia

in Annals of Clinical and Translational Neurology (2023), 10(9), 1682-1687

Synucleinopathies-related disorders such as Lewy body dementia (LBD) and isolated/idiopathic REM sleep behavior disorder (iRBD) have been associated with neuroinflammation. In this study, we examined ... [more ▼]

Synucleinopathies-related disorders such as Lewy body dementia (LBD) and isolated/idiopathic REM sleep behavior disorder (iRBD) have been associated with neuroinflammation. In this study, we examined whether the human leukocyte antigen (HLA) locus plays a role in iRBD and LBD. In iRBD, HLA-DRB1*11:01 was the only allele passing FDR correction (OR = 1.57, 95 CI = 1.27–1.93, p = 2.70e-05). We also discovered associations between iRBD and HLA-DRB1 70D (OR = 1.26, 95\%CI = 1.12–1.41, p = 8.76e-05), 70Q (OR = 0.81, 95\%CI = 0.72–0.91, p = 3.65e-04) and 71R (OR = 1.21, 95\%CI = 1.08–1.35, p = 1.35e-03). Position 71 (pomnibus = 0.00102) and 70 (pomnibus = 0.00125) were associated with iRBD. Our results suggest that the HLA locus may have different roles across synucleinopathies. [less ▲]

Education as risk factor of Mild Cognitive Impairment - the role of the gut microbiome

Poster (2023, July)

Polygenic risk scores validated in patient-derived cells stratify for mitochondrial subtypes of Parkinson\textquoterights disease 2023.05.12.23289877

E-print/Working paper (2023)

Background Parkinson's disease (PD) is the fastest growing neurodegenerative disorder, with affected individuals expected to double during the next 20 years. This raises the urgent need to better ... [more ▼]

Background Parkinson's disease (PD) is the fastest growing neurodegenerative disorder, with affected individuals expected to double during the next 20 years. This raises the urgent need to better understand the genetic architecture and downstream cellular alterations underlying PD pathogenesis, in order to identify more focused therapeutic targets. While only ~10\% of PD cases can be clearly attributed to monogenic causes, there is mounting evidence that additional genetic factors could play a role in idiopathic PD (iPD). In particular, common variants with low to moderate effect size in multiple genes regulating key neuroprotective activities may act as risk factors for PD. In light of the well-established involvement of mitochondrial dysfunction in PD, we hypothesized that a fraction of iPD cases may harbour a pathogenic combination of common variants in nuclear-encoded mitochondrial genes, ultimately resulting in neurodegeneration.Methods: To capture this mitochondria-related 'missing heritability', we leveraged on existing data from previous genome-wide association studies (GWAS) i.e., the large PD GWAS from Nalls and colleagues. We then used computational approaches based on mitochondria-specific polygenic risk scores (mitoPRSs) for imputing the genotype data obtained from different iPD case-control datasets worldwide, including the Luxembourg Parkinson\textquoterights Study (412 iPD patients and 576 healthy controls) and the COURAGE-PD cohorts (7270 iPD cases and 6819 healthy controls).Results: Applying this approach to gene sets controlling mitochondrial pathways potentially relevant for neurodegeneration in PD, we demonstrated that common variants in genes regulating Oxidative Phosphorylation (OXPHOS-PRS) were significantly associated with a higher PD risk both in the Luxembourg Parkinson\textquoterights Study (odds ratio, OR=1.31[1.14-1.50], p=5.4e-04) and in COURAGE-PD (OR=1.23[1.18-1.27], p=1.5e-29). Functional analyses in primary skin fibroblasts and in the corresponding induced pluripotent stem cells-derived neuronal progenitor cells from Luxembourg Parkinson's Study iPD patients stratified according to the OXPHOS-PRS, revealed significant differences in mitochondrial respiration between high and low risk groups (p < 0.05). Finally, we also demonstrated that iPD patients with high OXPHOS-PRS have a significantly earlier age at disease onset compared to low-risk patients.Conclusions: Our findings suggest that OXPHOS-PRS may represent a promising strategy to stratify iPD patients into pathogenic subgroups in which the underlying neurodegeneration is due to a genetically defined mitochondrial burden potentially eligible for future, more tailored mitochondrially targeted treatments. [less ▲]

Twist exome capture allows for lower average sequence coverage in clinical exome sequencing

in Human Genomics (2023), 17(1), 39

Background Exome and genome sequencing are the predominant techniques in the diagnosis and research of genetic disorders. Sufficient, uniform and reproducible/consistent sequence coverage is a main ... [more ▼]

Background Exome and genome sequencing are the predominant techniques in the diagnosis and research of genetic disorders. Sufficient, uniform and reproducible/consistent sequence coverage is a main determinant for the sensitivity to detect single-nucleotide (SNVs) and copy number variants (CNVs). Here we compared the ability to obtain comprehensive exome coverage for recent exome capture kits and genome sequencing techniques. Results We compared three different widely used enrichment kits (Agilent SureSelect Human All Exon V5, Agilent SureSelect Human All Exon V7 and Twist Bioscience) as well as short-read and long-read WGS. We show that the Twist exome capture significantly improves complete coverage and coverage uniformity across coding regions compared to other exome capture kits. Twist performance is comparable to that of both short- and long-read whole genome sequencing. Additionally, we show that even at a reduced average coverage of 70× there is only minimal loss in sensitivity for SNV and CNV detection. Conclusion We conclude that exome sequencing with Twist represents a significant improvement and could be performed at lower sequence coverage compared to other exome capture techniques. [less ▲]

Accurate long-read sequencing identified GBA variants as a major genetic risk factor in the Luxembourg Parkinson\textquoterights study 2023.03.29.23287880

E-print/Working paper (2023)

Heterozygous variants in the glucocerebrosidase GBA gene are an increasingly recognized risk factor for Parkinson's disease (PD). Due to the pseudogene GBAP1 that shares 96\% sequence homology with the ... [more ▼]

Heterozygous variants in the glucocerebrosidase GBA gene are an increasingly recognized risk factor for Parkinson's disease (PD). Due to the pseudogene GBAP1 that shares 96\% sequence homology with the GBA coding region, accurate variant calling by array-based or short-read sequencing methods remains a major challenge in understanding the genetic landscape of GBA-related PD. We established a novel long-read sequencing technology for assessing the full length of the GBA gene. We used subsequent regression models for genotype-phenotype analyses. We sequenced 752 patients with parkinsonism and 806 healthy controls of the Luxembourg Parkinson's study. All GBA variants identified showed a 100% true positive rate by Sanger validation. We found 12% of unrelated PD patients carrying GBA variants. Three novel variants of unknown significance (VUS) were identified. Using a structure-based approach, we defined a potential risk prediction method for VUS. This study describes the full landscape of GBA-related parkinsonism in Luxembourg, showing a high prevalence of GBA variants as the major genetic risk for PD. Our approach provides an important advancement for highly accurate GBA variant calling, which is essential for providing access to emerging causative therapies for GBA carriers. [less ▲]

Transferability of European-derived cardiometabolic polygenic risk scores in the South Asians and their interplay with family history 2023.03.20.23287470

E-print/Working paper (2023)

Background & Aims We aimed to investigate the effect of polygenic risk scores (PRSs) derived from individuals of European (EUR) ancestry on common diseases among individuals of South Asian (SAS) ancestry ... [more ▼]

Background & Aims We aimed to investigate the effect of polygenic risk scores (PRSs) derived from individuals of European (EUR) ancestry on common diseases among individuals of South Asian (SAS) ancestry in the UK Biobank (UKB). Additionally, we studied the interaction between PRS and family history (FH) in the same population.Methods To calculate the PRS, we used a previously published panel of SNPs derived from the EUR population and applied it to the individuals of SAS ancestry from the UKB study. We applied the PRS using summary statistics from genome-wide association studies (GWAS) for cardiometabolic and lifestyle diseases such as coronary artery disease (CAD), obesity, and type 2 diabetes (T2D). Each PRS was adjusted according to an individual\textquoterights predicted genetic ancestry to derive an adjusted PRS (aPRS). We calculated the percentiles based on aPRS and divided them according to the percentiles into three categories: low, intermediate, and high. Considering the intermediate-aPRS percentile as a reference, we compared the low and high aPRS categories and generated the odds ratio (OR) estimates.Results The risk of developing severe obesity for individuals of SAS ancestry was almost threefold higher for individuals with high aPRS than for those with intermediate aPRS, with an OR of 3.67 (95% CI = 2.47-5.48, P < 0.01). While the risk of severe obesity was lower in the low-aPRS group (OR = 0.19, CI = 0.05\textendash0.52, P < 0.01). Comparable results were found in the EUR data, where the low-PRS group had an OR of 0.26 (95% CI= 0.24-0.3, P < 0.01) and the high-PRS group had an OR of 3.2 (95% CI = 3.1-3.3, P < 0.01). We observed similar results for CAD and T2D. Further, we show that SAS individuals with a familial history of CAD and T2D with high-aPRS exhibit further higher risk to these diseases, thereby implying a greater genetic predisposition to these conditions.Conclusion Our findings suggest that using CAD, obesity, and T2D GWAS summary statistics predominantly from the EUR population have sufficient power to identify SAS individuals with higher genetic risk. With future GWAS recruiting more SAS participants and tailoring the PRSs towards SAS ancestry, we believe that the predictive power of PRS would improve. [less ▲]

Forensic DNA Phenotyping: a review on SNP panels, genotyping techniques, and prediction models

E-print/Working paper (2023)

In the past few years, forensic DNA phenotyping (FDP) has attracted a strong interest in the forensic research. Among the increasing publications, many have focused on testing the available panels to ... [more ▼]

In the past few years, forensic DNA phenotyping (FDP) has attracted a strong interest in the forensic research. Among the increasing publications, many have focused on testing the available panels to infer biogeographical ancestry (BGA) on less represented populations and understanding the genetic mechanisms underlying externally visible characteristics (EVC). However, there are currently no publications that gather all the existing panels limited to FDP and discuss the main technical limitations of the technique. In this review, we performed a bibliographic search in Scopus database of FDP-related literature, which resulted in a total of 48, 43 and 15 panels for BGA, EVC and both BGA and EVC inference, respectively. Here we provide a list of commercial and non-commercial FDP panels and the FDP limitations regarding the lack of harmonization in terms of terminology (i.e., categorization and measurement of traits) and reporting, the lack of genetic knowledge and environment influence to select markers and develop panels, and the debate surrounding the selection of genotyping technologies and prediction models and algorithms. In conclusion, this review aims to be an updated guide and to present an overview of the current FDP-related literature. [less ▲]