Polybromo protein BAF180 functions in mammalian cardiac chamber maturation

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Abstract
BAF and PBAF are two related mammalian chromatin remodeling complexes essential for gene expression and development. PBAF, but not BAF, is able to potentiate transcriptional activation in vitro mediated by nuclear receptors, such as RXRα, VDR, and PPARγ. Here we show that the ablation of PBAF-specific subunit BAF180 in mouse embryos results in severe hypoplastic ventricle development and trophoblast placental defects, similar to those found in mice lacking RXRα and PPARγ. Embryonic aggregation analyses reveal that in contrast to PPARγ-deficient mice, the heart defects are likely a direct result of BAF180 ablation, rather than an indirect consequence of trophoblast placental defects. We identified potential target genes for BAF180 in heart development, such as S100A13 as well as retinoic acid (RA)-induced targets RARβ2 and CRABPII. Importantly, BAF180 is recruited to the promoter of these target genes and BAF180 deficiency affects the RA response for CRABPII and RARβ2. These studies reveal unique functions of PBAF in cardiac chamber maturation.