Arid3a modulates the first cell fate decision by direct regulation of both embryonic and extraembryonic gene expression (ChIP-Seq)

Arid3a, a transcription factor known for its requirement in B-lymphocyte development, has been recently identified as a member of ES cell pluripotency network. Arid3a is moderately expressed in ES cells, and its expression is gradually increased during differentiation. Since Arid3a shows the highest expression in placenta, we hypothesized that Arid3a may play important roles in TE development. We report that Arid3a is a central regulator of both TE-specific and pluripotency-associated gene expression during ES cell differentiation. While dispensable for self-renewal, we observed that knockdown of Arid3a delays differentiation of ES cells. Induction of Arid3a leads ES cells to promote differentiation, specifically towards TE lineage. Moreover, these Arid3a-overexpressing cells maintained in TE culture media are sufficient to generate functional trophoblast stem-like cells, suggesting roles of Arid3a in TE differentiation. By integrative analyses using the chromosomal targets of Arid3a with expression profiling, we revealed the dual roles of Arid3a, as a direct activator of TE-specific genes and a repressor of pluripotency-associated genes. We further revealed the repressive roles of Arid3a are mediated by histone deacetylases (HDACs). Taken together, our results demonstrate that Arid3a is a critical novel regulator in TE lineage specification.