A DNMT3A PWWP mutation leads to methylation of bivalent chromatin and postnatal growth retardation in mice

DNA methyltransferases (DNMTs) deposit repressive DNA methylation, which regulates gene expression and is essential for mammalian development. Histone post-translational modifications can recruit DNMTs to DNA. The PWWP domains of DNMT3A and DNMT3B are posited to interact with histone 3 lysine 36 trimethylation (H3K36me3); however, the functionality of this interaction for DNMT3A remains untested in vivo. Here we present a mouse model carrying a D329A point mutation in the DNMT3A PWWP domain. The mutation causes dominant postnatal growth retardation. At the molecular level, it results in aberrant progressive acquisition of DNA methylation across domains marked by bivalent chromatin, resulting in de-repression of important developmental regulatory genes in adult hypothalamus. Evaluation of non-CpG methylation further demonstrates the altered recruitment and activity of mutant DNMT3A at bivalent domains. This work provides key molecular insights into analogous growth phenotypes observed in humans with congenital mutations in the DNMT3A PWWP domain. Overall design: There are at least two biological replicates per genotype per experiment, and a wild-type (reference) and mutant mouse comparison is always included.