REST elevation-dependent chromatin remodeling and alternative Grk6 transcript synthesis hyperactivates Cxcr4-Sdf1 signaling in cerebellar granule cell progenitors

RE1 Silencing Transcription Factor (REST) is a repressor of transcriptional initiation of genes involved in neurogenesis. Here, we show that conditional REST elevation in cerebellar granule cell progenitors (CGNPs) of REST ^TG mice perturbed foliation, increased cell migration, and sustained C-X-C motif receptor 4 (Cxcr4) signaling, a pathway key to postnatal CGNP migration. Mechanistic studies uncovered a novel role for REST in controlling transcript diversity and exon skipping in CGNPs. Alternative transcript expression was detected in known Cxcr4 signaling regulator, G-protein-coupled receptor kinase-6 ( Grk6 ). Further analysis of Grk6’s isoform expression revealed an upregulation of a transcript lacking exon 10a ( Grk6-207 ) in REST ^TG CGNPs. Grk6-207 expression in wildtype CGNPs hyperactivated Cxcr4 signaling and increased chemotaxis. Structural modeling of Grk6-207 predicted changes in active site conformation and interactions with Cxcr4 and β-Arrestin-1, supporting impairment of Cxcr4 signaling desensitization. Interestingly, REST elevation promoted increased chromatin accessibility at the exon10a-10b junction and exon 10a exclusion. Integrated multiomic analyses identified the enhancer of zeste (Ezh2) as a potential mediator of alternative transcript generation which demonstrated increased occupancy at the exon10a-10b locus in REST ^TG CGNPs. Pharmacological inhibition of Ezh2 downregulated Grk6-207 , confirming a role for Ezh2 in Grk6 exon10a exclusion and the increased migration in REST ^TG CGNPs.