Analysis of genetic variations associated with arrhythmogenic right ventricular cardiomyopathy

Cardiomyopathy accounts for 20-30% of acute heart failure cases in adult Africans. Several types of cardiomyopathy have been identified; this study focused primarily on the genetic causes of arrhythmogenic right ventricular cardiomyopathy (ARVC). Many genes are implicated in ARVC pathogenesis, but many remain to be identified. We investigated a South African family (ACM2) with autosomal dominant ARVC, for whom the genetic cause of disease was unknown. Extensive genetic analysis was previously performed using genome-wide linkage analysis, but no disease-causing genetic variant was identified. We subsequently performed candidate gene screening of the phospholamban (PLN) gene, genome-wide copy number variant (CNV) analysis and whole exome sequencing to identify the causal genetic variant. The ACM2 family harboured no disease-causing PLN variants. However, on screening all cardiomyopathy cases in our registry (ARVC, dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy and peripartum cardiomyopathy), we identified a known pathogenic PLN variant (c.25C>T; p.R9C) in a DCM family of European descent. This variant was reported in an American DCM family of European descent. Haplotype analysis revealed independent variant origins in these families. CNV analysis revealed no disease-causing variants in the ACM2 family. Whole exome sequencing of two affected ACM2 family members revealed 38 variants shared by these individuals. Variants were verified in family members and population controls by high resolution melt analysis and Sanger sequencing, and by bioinformatics analysis to predict variant pathogenicity. A novel N-cadherin (CDH2) c.686A>C (p.Q229P) variant segregated with ARVC in the ACM2 family and was bioinformatically predicted to be deleterious. An additional pathogenic CDH2 variant (c.1219G>A (p.D407N)) was identified in another individual with ARVC after screening 85 cases. These CDH2 variants were absent in normal population controls. Furthermore, alterations in Cdh2 are known to cause cardiomyopathy in rodent models. Taken together, these findings support the causal role of N-cadherin gene variants in human cardiomyopathy

Analysis of desmoplakin in arrythmogenic right ventricular cardiomyopathy

Includes bibliographical references (leaves 71-79).It has been shown that all forms of cardiomyopathy, including the dilated, hypertrophic, restrictive, and right ventricular arrhythmogenic forms, are found in African populations. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare muscle disease characterised by fibrofatty replacement of the right ventricular myocardium, leading to electrical instability and eventual heart failure. Dilated cardiomyopathy (DCM) is a disease characterised by a reduction in ventricular wall thickness which leads to reduced contractility and impaired ventricular function. Mutations that cause ARVC have been reported in five desmosomal and three non-desmosomal genes

Mutation analysis of the phospholamban gene in 315 South Africans with dilated, hypertrophic, peripartum and arrhythmogenic right ventricular cardiomyopathies

Cardiomyopathy is an important cause of heart failure in Sub-Saharan Africa, accounting for up to 30% of adult heart failure hospitalisations. This high prevalence poses a challenge in societies without access to resources and interventions essential for disease management. Over 80 genes have been implicated as a cause of cardiomyopathy. Mutations in the phospholamban (PLN) gene are associated with dilated cardiomyopathy (DCM) and severe heart failure. In Africa, the prevalence of PLN mutations in cardiomyopathy patients is unknown. Our aim was to screen 315 patients with arrhythmogenic right ventricular cardiomyopathy (n = 111), DCM (n = 95), hypertrophic cardiomyopathy (n = 40) and peripartum cardiomyopathy (n = 69) for disease-causing PLN mutations by high resolution melt analysis and DNA sequencing. We detected the previously reported PLN c.25C > T (p.R9C) mutation in a South African family with severe autosomal dominant DCM. Haplotype analysis revealed that this mutation occurred against a different haplotype background to that of the original North American family and was therefore unlikely to have been inherited from a common ancestor. No other mutations in PLN were detected (mutation prevalence = 0.2%). We conclude that PLN is a rare cause of cardiomyopathy in African patients. The PLN p.R9C mutation is not well-tolerated, emphasising the importance of this gene in cardiac function

AI is a viable alternative to high throughput screening: a 318-target study

: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery

Whole Genome Sequencing of SARS-CoV-2: Adapting Illumina Protocols for Quick and Accurate Outbreak Investigation during a Pandemic

The COVID-19 pandemic has spread very fast around the world. A few days after the first detected case in South Africa, an infection started in a large hospital outbreak in Durban, KwaZulu-Natal (KZN). Phylogenetic analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes can be used to trace the path of transmission within a hospital. It can also identify the source of the outbreak and provide lessons to improve infection prevention and control strategies. This manuscript outlines the obstacles encountered in order to genotype SARS-CoV-2 in near-real time during an urgent outbreak investigation. This included problems with the length of the original genotyping protocol, unavailability of reagents, and sample degradation and storage. Despite this, three different library preparation methods for Illumina sequencing were set up, and the hands-on library preparation time was decreased from twelve to three hours, which enabled the outbreak investigation to be completed in just a few weeks. Furthermore, the new protocols increased the success rate of sequencing whole viral genomes. A simple bioinformatics workflow for the assembly of high-quality genomes in near-real time was also fine-tuned. In order to allow other laboratories to learn from our experience, all of the library preparation and bioinformatics protocols are publicly available at protocols.io and distributed to other laboratories of the Network for Genomics Surveillance in South Africa (NGS-SA) consortium

Identification of Cadherin 2 (CDH2) Mutations in Arrhythmogenic Right Ventricular Cardiomyopathy

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically heterogeneous condition caused by mutations in genes encoding desmosomal proteins in up to 60% of cases. The 40% of genotype-negative cases point to the need of identifying novel genetic substrates by studying genotype-negative ARVC families. METHODS AND RESULTS: Whole exome sequencing was performed on 2 cousins with ARVC. Validation of 13 heterozygous variants that survived internal quality and frequency filters was performed by Sanger sequencing. These variants were also genotyped in all family members to establish genotype-phenotype cosegregation. High-resolution melting analysis followed by Sanger sequencing was used to screen for mutations in cadherin 2 (CDH2) gene in unrelated genotype-negative patients with ARVC. In a 3-generation family, we identified by whole exome sequencing a novel mutation in CDH2 (c.686A>C, p.Gln229Pro) that cosegregated with ARVC in affected family members. The CDH2 c.686A>C variant was not present in >200 000 chromosomes available through public databases, which changes a conserved amino acid of cadherin 2 protein and is supported as the causal mutation by parametric linkage analysis. We subsequently screened 73 genotype-negative ARVC probands tested previously for mutations in known ARVC genes and found an additional likely pathogenic variant in CDH2 (c.1219G>A, p.Asp407Asn). CDH2 encodes cadherin 2 (also known as N-cadherin), a protein that plays a vital role in cell adhesion, making it a biologically plausible candidate gene in ARVC pathogenesis. CONCLUSIONS: These data implicate CDH2 mutations as novel genetic causes of ARVC and contribute to a more complete identification of disease genes involved in cardiomyopathy

WDR62 is associated with the spindle pole and is mutated in human microcephaly.

Autosomal recessive primary microcephaly (MCPH) is a disorder of neurodevelopment resulting in a small brain. We identified WDR62 as the second most common cause of MCPH after finding homozygous missense and frame-shifting mutations in seven MCPH families. In human cell lines, we found that WDR62 is a spindle pole protein, as are ASPM and STIL, the MCPH7 and MCHP7 proteins. Mutant WDR62 proteins failed to localize to the mitotic spindle pole. In human and mouse embryonic brain, we found that WDR62 expression was restricted to neural precursors undergoing mitosis. These data lend support to the hypothesis that the exquisite control of the cleavage furrow orientation in mammalian neural precursor cell mitosis, controlled in great part by the centrosomes and spindle poles, is critical both in causing MCPH when perturbed and, when modulated, generating the evolutionarily enlarged human brain.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe