The SMARCA5-DMRT1 Pioneer Complex Establishes Epigenetic Priming to Direct Male Germline Development.

The establishment of cell type-specific chromatin landscapes is essential for cellular identity, but how these landscapes are generated remains poorly understood. Here, we demonstrate that the chromatin remodeler SMARCA5 establishes epigenetic priming that is required for retinoic acid (RA)-induced differentiation in the male germline. Germ cell-specific deletion of Smarca5 results in a complete loss of differentiating spermatogonia, phenocopying vitamin A-deficient mice that lack RA signaling. During the perinatal transition from prospermatogonia to undifferentiated spermatogonia, SMARCA5 is recruited to binding sites of the pioneer transcription factor DMRT1, which are located at distal putative enhancers and promoters of germline genes. The SMARCA5-DMRT1 pioneer complex establishes chromatin accessibility at these loci, generating poised enhancers and promoters that serve as RA receptor (RAR)-binding sites. Thus, SMARCA5 licenses transcriptional responses to RA that enable spermatogenic differentiation. Our findings uncover a mechanism linking pioneer factor activity to external signal responsiveness.