Hytonen, M. K. | Search bioRxiv

bioRxiv2024

A feline model of human LDLR-related atherosclerosis

BackgroundAtherosclerosis, a chronic inflammatory vascular disease driven by the accumulation of LDL-derived cholesterol on arterial walls, is the leading cause of mortality worldwide but is rare in animals. We recently identified spontaneous atherosclerosis in the Korat cat breed, characterized by severe hypercholesterolemia and clinical signs of congestive heart failure, ultimately leading to death. Histopathological examination revealed lesions similar to those observed in human atherosclerosis. Given the close genetic relationship among affected cats, we hypothesized a genetic basis for the condition. MethodsWe expanded our sample recruitment and employed whole genome sequencing to identify genetic variants associated with the condition. ResultsWe identified a homozygous XM_003981898.6:c.2406G>A variant specific to the cases in the LDLR gene. This variant is predicted to result in a premature stop codon, XP_003981947.3:p.Trp758*, leading to a truncated LDLR protein that lacks the last 108 amino acids, including the transmembrane and intracellular C-terminal domains. Genotyping this LDLR variant in an additional cohort of 309 Korat cats confirmed its segregation and revealed new affected cats for clinical follow-up. In silico analyses demonstrated that the identified variant appears optimal for gene-editing-based therapeutics. ConclusionsThis is the first report of a spontaneous atherosclerosis animal model with an LDLR variant, the most common gene associated with familial hypercholesterolemia in humans. Given that PCSK9, another known hypercholesterolemia gene, has been lost in many mammalian genomes, including cats, our study provides an exciting double knockout model for human atherosclerosis. The affected Korats may also serve as a valuable model for DNA base editing therapeutics.

genetics↗

bioRxiv2024

Determinants of de novo mutations in extended pedigrees of 43 dog breeds

Intensive breeding of dogs has had dramatic effects on genetic variants underlying phenotypes. To investigate whether this also affected mutation rates, we deep-sequenced pedigrees from 43 different dog breeds representing 404 trios. We find that the mutation rate is remarkably stable across breeds and is predominantly influenced by variation in parental ages. The effect of paternal age per year on mutation rates is approximately 1.5 times greater in dogs than humans, suggesting that the elevated yearly mutation rate in dogs is only partially attributed to earlier reproduction. While there is no significant effect of breeds on the overall mutation rate, larger breeds accumulate proportionally more mutations earlier in development than small breeds. Interestingly, we find a 2.6 times greater mutation rate in CG Islands (CGIs) compared to the remaining genome in dogs, unlike humans, where there is no difference. Our estimated rate of mutation by recombination in dogs is more than 10 times larger than estimates in humans. We ascribe these to the fact that canids have lost PRDM9-directed recombination and draw away recombination from CGIs. In conclusion, our study sheds light on stability of mutation processes and disparities in mutation accumulation rates reflecting the influence of differences in growth patterns among breeds, and the impact of PRDM9 gene loss on the de novo mutations of canids.

evolutionary biology↗