By controlling the access of transcription factors to individual genes,chromatin remodelling complexes help to regulate transcription. SWI2/SNF2 complexes contain one of two ATPases: brahma (BRM) or brahma-related gene 1(BRG1). By using temporally controlled somatic mutagenesis during mouse embryogenesis, Indra and co-workers report on p. that BRG1 has distinct functions in limb morphogenesis and in the final stages of skin formation. By selectively ablating Brg1 in embryonic surface ectoderm and fetal epidermal keratinocytes, the researchers show that ectodermal BRG1 expression is required for hindlimb morphogenesis–its absence reduces FGF8 expression, which is needed to maintain the apical ectodermal ridge. Epidermal BRG1 expression is also required during keratinocyte terminal differentiation but BRM can partly substitute for BRG1 here; neither protein is essential for keratinocyte proliferation or early differentiation. These results begin to identify the developmental functions of BRG1 and BRM.
