As ESCs differentiate into neuronal progenitors, the esBAF complex undergoes several subunit exchanges: it incorporates BRM and BAF60C and excludes BAF60B24,29 (Fig. 1a). BRG1 is required for the self-renewal of neuronal progenitors and for the normal differentiation of neurons from these progenitors24. BRG1-deficient neuronal progenitors misexpress key components of the NOTCH-and sonic-hedgehog-signalling pathways, which direct neurogenesis24. BAF45A is sufficient to induce the proliferation of neuronal progenitors past their normal mitotic exit point24. As neuronal progenitors leave their stem-cell niche in the subventricular zone of the brain and exit from mitosis, they express BAF45B and BAF53B, which replace BAF45A and BAF53A in the neuronal-progenitor-specific BAF (npBAF) complex to form a neuron-specific BAF (nBAF) complex24. The nBAF complex promotes activity-dependent dendritic outgrowth by interacting with the Ca2+-responsive dendritic regulator CREST (also known as SS18L1), thereby directly regulating genes essential for dendritic outgrowth13. The function of BAF53B in dendritic morphogenesis cannot be replaced by BAF53A, demonstrating the functional specialization of BAF complexes of different compositions. Genes encoding several subunits of BAF complexes were also found in an RNAi screen for factors involved in
