Mechanisms controlling the proliferative activity of neural stem and progenitor cells (NSPCs) have a pivotal role to ensure life-long neurogenesis in the mammalian brain1. How metabolic programs are coupled with NSPC activity remains unknown. Here we show that fatty acid synthase (Fasn), the key enzyme of de novo lipogenesis2, is highly active in adult NSPCs and that conditional deletion of Fasn in mouse NSPCs impairs adult neurogenesis. The rate of de novo lipid synthesis and subsequent proliferation of NSPCs is regulated by Spot14, a gene previously implicated in lipid metabolism3–5, that we found to be selectively expressed in low proliferating adult NSPCs. Spot14 reduces the availability of malonyl-CoA6, which is an essential substrate for Fasn to fuel lipogenesis. Thus, we identify here a functional coupling between the regulation of lipid metabolism and adult NSPC proliferation.

The opposition between polycomb repressive complexes (PRC) and BAF (mSWI/SNF) complexes plays critical roles in development and disease. Mutations in the genes encoding BAF subunits contribute to over 20% of human malignancy, yet the underlying mechanisms remain unclear owing largely to a lack of assays to assess BAF function in vivo. To address this, we have developed a widely applicable recruitment assay system and find that BAF opposes PRC by rapid, ATP-dependent eviction, leading to the formation of accessible chromatin. Reversing this process results in reassembly of facultative heterochromatin. Surprisingly, BAF-mediated PRC eviction occurs in the absence of PolII occupancy, transcription, and replication. Further, we find that tumor suppressor and oncogenic BAF complex mutations result in differential effects on PRC eviction. These studies define a mechanistic sequence underlying the resolution and formation of facultative heterochromatin and demonstrate that BAF opposes polycomb complexes on a minute-by-minute basis to provide epigenetic plasticity.

Trithorax-group genes and mammalian homologues, including BAF (mSWI/SNF) complexes, have been known for nearly 30 years to oppose Polycomb repressive activity1–5. This opposition underlies the tumor-suppression role of BAF3,5–7 and is expected to contribute to neurodevelopmental disorders, as evidenced by frequent driving mutations8,9. However, the mechanisms underlying opposition to Polycomb silencing are poorly understood. Here we report that recurrent disease mutations of BAF subunits induce genome-wide increases in Polycomb complex deposition and activity. We show that point mutations of the Smarca4 (Brg) ATPase domain cause loss of direct binding between BAF and PRC1 that occurs independently of chromatin. Release of this direct interaction occurs via an ATP-dependent mechanism, consistent with a role as a transient intermediate of eviction. Using a new in vivo assay, we find that BAF directly evicts Polycomb factors within minutes of its occupancy, together establishing a new mechanism for the widespread opposition underlying development and disease.