Project description:Prolonged electrocardiographic indices reflecting myocardial impulse conduction and repolarization are risk factors for sudden cardiac death and drug-induced arrhythmia. The PR-interval, QRS-duration and QT-interval are heritable traits influenced by multiple genetic and environmental factors. The genetic underpinnings of these traits are still largely unknown. In this study, we leveraged the variability in cardiac gene expression and the variation in PR-, QRS- and QT-intervals among F2 mice harboring the cardiac sodium ion-channel mutation Scn5a-1798insD/+ derived from the 129P2-Scn5a1798insD/+ and FVB/NJ-Scn5a1798insD/+ cross, to isolate novel genes and biological pathways impacting on cardiac conduction and repolarization. Cardiac left-ventricle total RNA from 120 F2-(129P2xFVBN/J)-Scn5a-1798insD/+ mice at 12 to 14 weeks old.
Project description:Conduction slowing of the electric impulse that drives the heartbeat may evoke lethal cardiac arrhythmias. Mutations in SCN5A, which encodes the pore-forming cardiac sodium channel alpha subunit, are associated with familial arrhythmia syndromes based on conduction slowing. However, disease severity among mutation carriers is highly variable. We hypothesized that genetic modifiers underlie the variability in conduction slowing and disease severity. With the aim of identifying such modifiers, we studied the Scn5a(1798insD/+) mutation in 2 distinct mouse strains, FVB/N and 129P2. In 129P2 mice, the mutation resulted in more severe conduction slowing particularly in the right ventricle (RV) compared to FVB/N. Pan-genomic mRNA expression profiling in the 2 mouse strains uncovered a drastic reduction in mRNA encoding the sodium channel auxiliary subunit beta4 (Scn4b) in 129P2 mice compared to FVB/N. This corresponded to low to undetectable beta4 protein levels in 129P2 ventricular tissue, whereas abundant beta4 protein was detected in FVB/N. Sodium current measurements in isolated myocytes from the 2 mouse strains indicated that sodium channel activation in myocytes from 129P2 mice occurred at more positive potentials compared to FVB/N. Using computer simulations, this difference in activation kinetics was predicted to explain the observed differences in conduction disease severity between the 2 strains. In conclusion, genetically determined differences in sodium current characteristics on the myocyte level modulate disease severity in cardiac sodium channelopathies. In particular, the sodium channel subunit beta4 (SCN4B) may constitute a potential genetic modifier of conduction and cardiac sodium channel disease.
Project description:We collected whole genome testis expression data from hybrid zone mice. We integrated GWAS mapping of testis expression traits and low testis weight to gain insight into the genetic basis of hybrid male sterility.
Project description:Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are used to examine in vitro the effect of mutations in the cardiac sodium channel gene SCN5A, associated with cardiac arrhythmias. Postnatally SCN5A undergoes a fetal-to-adult isoform switch, but hiPSC-CMs in conventional 2-dimensional cultures are fetal-like. This impedes evaluation of mutations in the adult isoform. Here, we derived hiPSC-CMs from a patient carrying compound mutations in the adult SCN5A exon 6B and in exon 4 and generated isogenic corrected lines. In hiPSC-CM 2-dimensional culture, exon 6B mutation did not affect single-cell electrophysiology because of its limited expression. CRISPR/Cas9-mediated excision of the fetal exon 6A with did not promote adult SCN5A expression, rather it impaired the splicing. By maturing hiPSC-CMs in three-dimensional tri-cell type cardiac microtissues, SCN5A underwent isoform switch and revealed the functional effect of exon 6B mutation. Upregulation of the splicing factor MBNL1 in hiPSC-CMs either by culture in microtissues or by overexpression was sufficient to promote exon 6B inclusion. Our results support the ability to study developmentally regulated cardiac genes and postnatal cardiac arrhythmias using hiPSC cardiac cells.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.