The spreading of facultative H3K9me3-heterochromatin drives congenital disease

Heterochromatin marked by trimethylated histone 3 at lysine 9 (H3K9me3) plays fundamental roles in reprogramming to direct cell fate determination in higher eukaryotes. However, the upstream factors that guide the establishment and spreading of H3K9me3-heterochromatin, leading to human developmental malformations, remain elusive. In this study, we found that Cdk13, a member of RNA polymerase II (RNAPII) kinase, suppresses congenital heart syndrome by preventing global facultative H3K9me3-heterochromatin spreading. Additionally, Cdk13 directs the phosphorylation of a large set of heterochromatin proteins at specific sites, which are required for the interaction between HP1 and histone H3K9 methyltransferases. Furthermore, we identified a compound, an inhibitor of heterochromatin regulators, that can alleviate syndromic heart defects in Cdk13-mutant mice through the inhibition of H3K9me3-heterochromatin spreading. In summary, this study reveals a novel role and mechanism of Cdk13-triggered facultative H3K9me3-heterochromatin spreading in human genetic disease and paves the way for the treatment of congenital heart syndrome.