Unraveling the genetics of feline hypertrophic cardiomyopathy: a multiomics study of 138 cats

Abstract

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease in cats, often leading to congestive heart failure, arterial thromboembolism, and sudden cardiac death. The genetics of feline HCM are poorly understood and limited genetic discoveries remain breed- or family-specific. We aimed to identify novel causative or disease-modifying variants in a large cohort of cats reflective of the general cat population. In a second cohort, we sought to characterize transcriptomics differences between HCM-affected cats and healthy controls. DNA was isolated from 138 domestic cats (109 HCM and 29 controls). No single or combination of variants of high, moderate, or modifying impact were identified by genome-wide analysis to cause or modify disease severity of HCM. Several rare high and moderate impact variants in genes associated with human HCM were detected in diseased cats. In a second cohort, left ventricular (LV), interventricular septal (IVS), and left atrial (LA) tissues of 27 HCM-affected and 15 control cats were submitted for stranded mature RNA-sequencing at 50 million reads/sample. A total of 74, 115, and 45 differentially expressed genes (DEGs) were upregulated and 8, 53, and 48 DEGs were downregulated in LV posterior wall, IVS, and LA tissue, respectively, in HCM-affected cats compared to controls. Similar to humans, the genetic etiology of feline HCM remains unknown in a high proportion of cases. Transcriptomics revealed molecular signatures that may help identify novel HCM biomarkers or drug targets in future investigations.

Keywords: RNA-sequencing; cardiovascular; precision medicine; translational; whole-genome sequencing.

Fig. 1.

a) GWAS of HCM cases vs controls displayed as a Manhattan plot. Only variants with a P-value <0.01 are displayed. Genome-wide significance is shown as a dashed red line. b) QQ plot generated from a subset of 2 million unlinked variants, only P-values <0.1 are displayed. c) A zoomed-in plot of the peak on C1. Protein coding genes and their orientation are displayed along with coding sequence boundaries. Colors reflect the linkage disequilibrium r² from the lead variant. d) Zoomed-in plot of the peak on E1.

Fig. 2.

a) QQ plot for single gene association tests in HCM vs control. Colors represent different models, and the red dashed horizontal line represents the threshold based on Bonferroni correction. Panes reflect aggregation of high impact (number of tests = 255), moderate impact (number of tests = 6,419), and both high and moderate impact (number of tests = 6,904) variants combined. b) Association of high or moderate impact rare variants aggregated by panels of increasing breadth (see Supplementary Table 3). Different colors represent different statistical tests, and the vertical dashed line indicates the P = 0.05.

Fig. 3.

a) The number of rare high and moderate impact variants found in each sample. Counts negate whether a variant was found as a heterozygote or homozygote. Individual samples are represented along the x-axis and partitioned into their HCM or control cohorts. Color is scaled to the number of variants found in each sample, for each gene. b) Number of moderate impact variants only found in HCM cats (not in any control cats) per gene. c) Number of moderate impact variants only found in control cats (not in any HCM cats) per gene.

Fig. 4.

PCA plots demonstrating variance of gene expression between HCM-affected and cardiovascularly normal cats in a) LVPW, b) IVS, and c) LA tissue. Circles represent females; squares represent males; colors reflect ACVIM status. d), e), and f) show volcano plots indication log2fold expression changes between control and HCM cats. Genes significantly upregulated and downregulated in HCM cats are colored red and blue respectively for d) LVPW, e) IVS, and f) LA tissue. The top 10 protein coding DEGs according to P-value are shown.

Fig. 5.

GSEA results for GO BPs in the a) LVPW, b) IVS, and c) LA tissue. The size of each point is proportional to the number of genes associated with each term. Up to the top 10 terms are listed that were up- and down-regulated in HCM cats.