Epigenetics of genes preferentially expressed in dissimilar cell populations: Myoblasts and cerebellum

Very disparate types of cell populations exhibit similar transcription specificity for certain genes. We identified 20 genes that were expressed preferentially in myoblasts and cerebellum (Myob/Cbl genes) and examined their cell/tissue-specific epigenetics using a combined approach of comparing DNA methylation, chromatin accessibility, and RNA expression in many different cell populations. Some Myob/Cbl genes shared DNA hypo- or hypermethylated regions in myoblasts and cerebellum. Particularly striking was ZNF556, whose promoter is hypomethylated in expressing cells but highly methylated in the many cell populations that do not express the gene. In reporter gene assays, we demonstrated that its promoter’s activity is methylation-sensitive. The atypical epigenetics of ZNF556 may have originated from its promoter’s hypomethylation and selective activation in sperm progenitors and oocytes. Five of the Myob/Cbl genes (KCNJ12, ST8SIA5, ZIC1, VAX2, and EN2) have much higher RNA levels in cerebellum than in myoblasts and displayed myoblast-specific hypermethylation upstream and/or downstream of their promoters that may downmodulate expression. Differential DNA methylation was associated with alternative promoter usage for Myob/Cbl genes MCF2L, DOK7, CNPY1, and ANK1. Myob/Cbl genes PAX3, LBX1, ZNF556, ZIC1, EN2, and VAX2 encode sequence-specific transcription factors, which likely help drive the myoblast and cerebellum specificity of other Myob/Cbl genes. Our study extends our understanding of epigenetic/transcription associations related to differentiation and may help elucidate relationships between epigenetic signatures and muscular dystrophies or cerebellar-linked neuropathologies.