Abstract 13979: Titin-Truncating Variants Predispose to Dilated Cardiomyopathy in Patients Genetically Similar to African Reference Populations

Abstract

Introduction: Heterozygous mutations within the TTN gene can cause the translation of shortened forms of the titin protein known as titin-truncating variants (TTNtvs) leading to dilated cardiomyopathy (DCM) among certain individuals. We previously reported an odds ratio (OR) of 18.7 for DCM among individuals genetically similar to the European reference population (EUR) with high percentage spliced in (hiPSI) TTNtvs, however we were unable to show a similar relationship among individuals genetically similar to the African reference population (AFR). Methods: Penn Medicine Biobank volunteers with whole exome sequencing were screened for TTNtvs with minor allele frequency <0.001 and percent spliced in >0.9. Participants were also screened for a DCM diagnosis defined using International Classification of Diseases, ninth and tenth revision diagnoses codes. Left ventricular ejection fraction (LVEF) values were extracted from structured transthoracic echocardiography reports. Logistic and linear regression were employed to evaluate the association between hiPSI TTNtvs and DCM or LVEF adjusting for age, sex, and first five genetic principal components. Results: Of the 43,731 participants with sequencing data, 11,136 (27.1%) were genetically similar to the AFR reference population, 50.3% were male, and the median age was 57.8 years (IQR: 44.9-69.5 years). One percent (418 individuals) had a hiPSI TTNtv. The age- and sex-adjusted OR of having DCM was similar among AFR and EUR participants carrying hiPSI TTNtvs (AFR OR: 4.37, 95% CI 2.68 to 7.13, P < 0.001; EUR OR: 5.86, 95% CI 4.58 to 7.49, P < 0.001; meta OR: 5.48, 95% CI 4.31 to 6.97, P < 0.001). Among those individuals with echocardiography data available, hiPSI TTNtvs were associated with significantly decreased minimum LVEF independent of genetic reference population similarity (EUR β: -10.08, 95% CI -12.71 to -7.44, P < 0.001; AFR β: -12.83, 95% CI -18.39 to -7.27, P < 0.001; Meta β: -10.58, 95% CI -12.96 to -8.20, P < 0.001). Conclusions: Our analysis demonstrates a strong association between hiPSI TTNtv and both DCM and minimum LVEF in diverse populations suggesting that genetic testing and counseling recommendations should not differ between these populations.