Dual mitotic bookmarking by GAF and H3K27ac orchestrates differential propagation of cell fate memory in neural development.

In brain development, neural stem cells (NSCs) undergo asymmetric cell divisions to replicate themselves and meanwhile produce differentiating siblings. It remains obscure how NSCs preserve their self-renewing fate across mitosis. Even less is known how cell fate memory is differentially propagated to sibling daughter cells adopting distinct cell fates. Here we found that key differentiation genes are dually bookmarked by pioneer factor GAF (GAGA factor) and H3K27ac in asymmetrically-dividing Drosophila central brain NSCs. In daughter cells adopting NSC fate, GAF promotes self-renewal through timely inhibiting differentiation genes via HDAC1-mediated H3K27 deacetylation, whereas in sibling daughter cells adopting neural progenitor fate, GAF occupancy is replaced by competitor SWI/SNF complex, allowing retention of H3K27ac mark and fast activation of differentiation genes. Thus, our study unveils a paradigm by which cell fate memory can be differentially transmitted to sibling daughter cells via dual antagonistic mitotic bookmarking and selective molecular competition mechanism.