Abstract
The mechanisms by which gene expression is activated at the chromatin level are poorly understood. The Epidermal Differentiation Complex (EDC), locus whose genes are expressed upon keratinocyte differentiation, provides a unique opportunity to address this question. Previously we identified a role for the epidermal-specific 923 enhancer in dynamic chromatin remodeling. Here we sought to investigate whether 923 is necessary for EDC activation using CRISPR/Cas9-mediated deletion. 923-/- KO mice (both 923delA and 923delB) appeared phenotypically normal under homeostatic conditions. However, transcriptional profiling of 923delA-/- embryonic skin captured during epidermal development (E14.5–NB) revealed decreased proximal gene expression of involucrin (Ivl), late cornified envelope 6a (Lce6a), and sperm mitochondrial-associated cysteine rich protein (Smcp). The requirement for the 923 enhancer was further validated in 923delB-/- newborn keratinocytes. ATAC-seq in 923delA-/- and wild-type littermate newborn keratinocytes further identified more closed chromatin (fewer ATAC-seq peaks) observed at the 5’ and 3’ ends of the EDC in 923delA-/-, indicating a requirement for the 923 enhancer for chromatin organization at the EDC boundaries. Male fertility defects associated with decreased 923 enhancer target gene Smcp expression in 923delA-/- male testes were observed with reduced progeny and slower sperm motility. Our genomic study reporting in vivo functional effect for the deletion of an epidermal-specific enhancer, identifies a requirement for 923 in proximal Ivl, Lce6a, and Smcp target gene expression, higher level chromatin accessibility in the EDC, and downstream male fertility function for its Smcp target gene, thus addressing a knowledge gap for enhancer function in chromatin level gene expression.
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