Short-Chain Enoyl-CoA Hydratase Mediates Histone Crotonylation and Contributes to Cardiac Homeostasis

osttranslational modifications of histones are critically involved in gene expression and regulate pathophysiologic processes such as cardiovascular diseases.Metabolic enzymes modulate the intracellular levels of metabolites to support posttranslational modifications. 1 Recently, new histone acylations have been identified to regulate gene expression.For example, histone crotonylation (H3K18cr and H2BK12cr) can trigger gene transcription and regulate metabolism, DNA repair, depression, and reproductive development.2 The roles of histone crotonylation in pathophysiologic processes of cardiovascular diseases-cardiac hypertrophy, for example-remain unknown.Short-chain enoyl-coenzyme A (CoA) hydratase (encoded by ECHS1) is a hydratase that has the highest activity for hydrolyzing crotonyl-CoA, reducing intracellular crotonyl-CoA, the orchestrator of histone crotonylation (Figure [A]).2,3 In human newborns or children, mutations in the ECHS1 gene lead to cardiomyopathies (>60%), such as hypertrophic cardiomyopathy, with unknown mechanisms.3,4 Downregulation of ECHS1 was observed in human hearts with hypertrophic cardiomyopathy (Figure [B]).ECHS1 downregulation was coupled with the upregulation of H3K18cr and H2BK12cr (Figure [C]), suggesting the involvement of ECHS1 and histone crotonylation in cardiac hypertrophy.To understand the roles of ECHS1 in cardiac hypertrophy, we generated 3 lines of germline Echs1 mutant mice with CRISPR-Cas9.However, no homozygote of Echs1 mutation was obtained, which might be attributable to the embryonic death induced by Echs1 knockout.Echs1 expression in heart tissues of Echs1 +/- mice was decreased to ≈50%, and Echs1 +/-mice developed normally (Figure [D] and data not shown).Cardiac hypertrophy in male adult Echs1 deficient (Echs1 +/-) and littermate wild-type (Echs1 +/+ ) mice was induced by a chronic infusion of angiotensin II (Ang II).Ang II treatment significantly increased heart weight, which was further enhanced in Echs1 +/-mice (Figure [E]).Histologic analysis showed that Echs1 deficiency promoted the increase in heart and cardiomyocyte size induced by Ang II (Figure [E]).We also analyzed whether ECHS1 regulated cardiac hypertrophy by directly targeting cardiomyocytes.Echs1 was knocked down with siRNA in neonatal rat cardiomyocytes (NRCMs) and cardiomyocyte hypertrophy was induced by Ang II.Echs1 knockdown alone induced hypertrophic growth and promoted the prohypertrophic effects of Ang II (Figure [F]).To test whether rescuing ECHS1 expression can repress hypertrophic growth of NRCMs, ECHS1 was overexpressed in NRCMs with adenovirus.ECHS1 overexpression repressed Ang II-induced increase in cardiomyocyte size (Figure [F]).To further investigate whether ECHS1 expression in cardiomyocytes can repress cardiac hypertrophy in vivo, we generated 2 lines of mice with cardiomyocyte-specific ECHS1 overexpression.Among them, 1 line moderately expressed ECHS1 and Short-Chain Enoyl-CoA Hydratase Mediates Histone Crotonylation and Contributes to Cardiac Homeostasis