Novel mouse model of Weaver syndrome displays overgrowth and excess osteogenesis reversible with KDM6A/6B inhibition

Abstract

AbstractWeaver syndrome is a Mendelian disorder of the epigenetic machinery (MDEM) caused by germline pathogenic variants inEZH2, which encodes the predominant H3K27 methyltransferase and key enzymatic component of Polycomb repressive complex 2 (PRC2). Weaver syndrome is characterized by striking overgrowth and advanced bone age, intellectual disability, and distinctive facies. We generated a mouse model for the most common Weaver syndrome missense variant,EZH2p.R684C.Ezh2R684C/R684Cmouse embryonic fibroblasts (MEFs) showed global depletion of H3K27me3.Ezh2R684C/+mice had abnormal bone parameters indicative of skeletal overgrowth, andEzh2R684C/+osteoblasts showed increased osteogenic activity. RNA-seq comparing osteoblasts differentiated fromEzh2R684C/+andEzh2+/+bone marrow mesenchymal stem cells (BM-MSCs) indicated collective dysregulation of the BMP pathway and osteoblast differentiation. Inhibition of the opposing H3K27 demethylases Kdm6a/6b substantially reversed the excessive osteogenesis inEzh2R684C/+cells both at the transcriptional and phenotypic levels. This supports both the ideas that writers and erasers of histone marks exist in a fine balance to maintain epigenome state, and that epigenetic modulating agents have therapeutic potential for the treatment of MDEMs.