Roles of REST and CoREST in mediating cell diversity in the early embryonic telencephalon

Abstract

Repressor Element 1 Silencing Transcription Factor (REST)/Neural Restrictive Silencing Factor (NRSF) is a zinc-finger transcriptional repressor that silences neuron-specific gene expression in non-neuronal cells by binding to repressor element 1 (RE1) DNA regions. Approximately 6,000 potential RE1 sites exist in the murine genome, the majority of which encode genes involved in ion channels, axonal guidance, neurotransmitter receptors, cell metabolism, synaptic vesicle proteins, and intracellular signaling. Gene silencing occurs via the recruitment of co-repressors, including Sin3A and CoREST, which mediate gene repression by recruiting epigenetic factors that includes histone dependent chromatin remodeling factors. To examine whether or not any cell-specific bias exists for the molecular actions of REST, we isolated mouse embryonic stem cells and, under specific growth factor conditions, generated largely pure populations of different neuronal and glial subtypes. In all cell types examined with immunocytochemistry, REST demonstrates nuclear and perinuclear expression, while CoREST demonstrates solely nuclear expression. This suggests that these factors orchestrate cell-type specificity throughout cellular development by differential binding to target genes. In order to take an unbiased molecular approach towards identifying in vivo REST and CoREST target genes during different stages of neural lineage maturation, we have used chromatin immunoprecipitation and a high-resolution 5kb mouse promoter array (ChIP-chip assay). We performed a series of ChIP-chip and gene expression assays in 11 different primary neural cell-types. This study is the first of its kind to take an unbiased, in vivo approach towards globally describing the REST binding profile in early non-neuronal cells. We have shown that REST, CoREST, and REST-CoREST modulate the expression and functions of distinct sets of genes involved in defining specific neural cell-type identities and seminal developmental transition states. While REST appears to mediate these functions throughout neural development, CoREST preferentially functions in maintenance of and transition from the NSC state as well as in progressive OL lineage maturation.