<scp>CHD4</scp> Ensures Bovine Early Embryogenesis by Restricting Developmental Gene Expression and Maintaining <scp>BRG1</scp> Expression

ATP-dependent chromatin remodeling proteins are essential for regulating gene expression and chromosome function in both invertebrate and vertebrate species. However, the precise manner in which these proteins influence mammalian embryogenesis is not well understood. Recent studies have shown that the chromatin remodeling ATPase CHD4 plays a role in forming a functional trophectoderm and in blastocyst implantation in mice. Nevertheless, more research is needed to clarify the species-specific function of CHD4. Here, we demonstrate that depleting CHD4 in bovine embryos results in failure to form blastocyst and developmental arrest at the 16-32-cell stage, when CHD4 protein increases dramatically. We compared transcript levels in 16-cell embryos to identify the consequences of CHD4 loss. This analysis revealed 652 differentially expressed genes, a substantial proportion of which were developmental genes. ATAC-seq further revealed that differential gene expression was closely associated with altered chromatin accessibility. Immunofluorescence analyses revealed additional changes in histone modifications, including increased levels of H3K27ac and H3K9me3, in CHD4-depleted embryos. Notably, CHD4 depletion promotes the transcriptional activity of trophectoderm marker keratins (KRTs) before first lineage specification, accompanied by a global increase in chromatin accessibility. Furthermore, CHD4 depletion markedly reduced BRG1, a key ATP-dependent remodeler in the SWI/SNF complex. Collectively, our results reveal that CHD4 is necessary to restrict the expression of developmental genes and maintain the expression of BRG1 during early bovine development to ensure the transition from the 16-cell to the 32-cell stage.