During neurogenesis, chromatin remodelling is required for the activation of proneural-activated genes, which are important for normal neuronal differentiation. The SWR1 complex regulates this process by catalysing the incorporation of the H2A.Z histone variant into nucleosomes, which impacts chromatin accessibility and transcriptional activation of proneural genes. However, the precise function of actin-related protein 6 (Arp6), a core component of the SWR1 complex, in this process has not been studied. Now, Haiwei Pi and colleagues use the Drosophila sensory organ as a model to investigate the effects of Arp6 mutation on neurogenesis. They find that Arp6 mutant flies display smaller sensory organ bristles, which can be attributed to reduced transcription in sensory organ precursors (SOPs) and to concomitant perturbation of SOP differentiation and division. Interestingly, enhanced expression of proneural genes, such as achaete (ac), could not rescue the phenotypes of Arp6 mutants, suggesting that Arp6 acts downstream or in parallel to proneural proteins. Supporting this hypothesis, the authors show that Arp6 promotes incorporation of H2A.Z into nucleosomes around the transcriptional start sites of Achaete target genes and thus enhances gene expression. Overall, this study highlights the importance of SWR1-mediated histone exchange in neuronal differentiation and the role of Arp6 in regulating proneural target gene expression.
