Biology subjects

Roberts, J. D.

Publications and source records attributed to Roberts, J. D..

3 recordsLinked to original sources

bioRxiv2023

Patient and cell-type specific hiPSC-modeling of a truncating titin variant associated with atrial fibrillation

BackgroundProtein truncating mutations in the titin gene are associated with increased risk of atrial fibrillation (AF). However, little is known regarding the underlying pathophysiology. MethodsWe identified a heterozygous titin truncating variant in a patient with unexplained early-onset AF using whole exome sequencing. We used atrial and ventricular patient induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), CRISPR/Cas9 genetic correction, and engineered heart tissue (EHT) constructs to evaluate the impact of the titin truncating variant on electrophysiology, sarcomere structure, contractility, and gene expression. ResultsWe generated atrial and ventricular iPSC-CMs from the AF patient with the titin truncating variant and a CRISPR/Cas9 genome corrected isogenic control. We demonstrate that the titin truncating variant increases susceptibility to pacing-induced arrhythmia (prevalence of arrhythmogenic phenotypes, 85.7% versus 14.2%; P = 0.03), promotes sarcomere disorganization (mean {+/-} SEM, 66.3 {+/-} 6.8% versus 88.0 {+/-} 2.9%; P = 0.04) in atrial iPSC-CMs, and reduces contractile force (0.013 {+/-} 0.003 mN versus 0.027 {+/-} 0.004 mN; P < 0.01) in atrial EHTs compared to isogenic controls. In ventricular iPSC-CMs, this variant led to altered electrophysiology (90.0% versus 33.3%; P = 0.02) and sarcomere organization (62.0 {+/-} 3.9% versus 82.9 {+/-} 2.9%; P < 0.01) with no change in EHT contractility compared to isogenic controls. RNA-sequencing revealed an upregulation of cell adhesion and extracellular matrix genes in the presence of the titin truncating variant for both atrial and ventricular EHTs. ConclusionsIn a patient with early-onset unexplained AF and normal ventricular function, iPSC-CMs with a titin truncating variant showed structural and electrophysiological abnormalities in both atrial and ventricular preparations, while only atrial EHTs demonstrated reduced contractility. Whole transcriptome sequencing showed upregulation of genes involved in cell-cell and cell-matrix interactions in both atrial and ventricular EHTs. Together, these findings suggest titin truncating variants promote the development of AF through remodeling of atrial cardiac tissue and provide insight into the chamber-specific effects of titin truncating variants.

cell biology↗

bioRxiv2021

Do exercise-associated genes explain phenotypic variance in the three components of fitness? A Systematic review & Meta-analysis.

The aim of this systematic review and meta-analysis was to identify a list of common, candidate genes associated with the three components of fitness, specifically cardiovascular fitness, muscular strength, and anaerobic power, and how these genes are associated with exercise response phenotype variability, in previously untrained participants. A total of 3,969 potentially relevant papers were identified and processed for inclusion. After eligibility and study selection assessment, 24 studies were selected for meta-analysis, comprising a total of 3,012 participants. Meta-Essentials spreadsheet 1.4 (Microsoft Excel) was used in creating the forest plots and meta-analysis. IBM SPSS statistics V24 was implemented for the statistical analyses and the alpha was set at p [≤] 0.05. 13 candidate genes and their associated alleles were identified, which were associated with the phenotypes of interest. Analysis of training group data showed significant differential phenotypic responses. Subgroup analysis showed; 44%, 72% and 10% of the response variance in aerobic, strength and power phenotypes, respectively, were explained by genetic influences. This analysis established that genetic variability explained a significant proportion of the adaptation differences across the three components of fitness in the participants post-training. The results also showed the importance of analysing and reporting specific gene alleles. Information obtained from these findings has the potential to inform and influence future exercise-related genes and training studies.

physiology↗

bioRxiv2017

A class of GATA3 mutation reprograms the breast cancertranscriptional network through gain and loss of function

GATA3 is frequently mutated in breast cancer; these mutations are widely presumed to be loss of function. Here, we address molecular alterations downstream of a novel class of GATA3 mutations, revealing both gain and loss of function. Mutation of one allele of GATA3 led to loss of binding and decreased expression at a subset of genes, including Progesterone Receptor. At other loci, associated with epithelial to mesenchymal transition, gain of binding at a novel sequence motif correlated with increased gene expression. These results demonstrate that not all GATA3 mutations are equivalent and that these mutations impact breast cancer through gain and loss of function.

cell biology↗