PRDM16 functions as a co-repressor in the BMP pathway to suppress neural stem cell proliferation
BMP signalling acts as an instructive cue in various developmental processes such as tissue patterning, stem cell proliferation, and differentiation. However, it is not fully understood how this signalling pathway generates different cell-specific outputs. Here we have identified PRDM16 as a key co-factor for BMP signalling. PRDM16 contributes to a repressive role of BMP signalling on neural stem cell (NSC) proliferation. We demonstrate that PRDM16 regulates the genomic distribution of BMP pathway transcription factors, the SMAD4/pSMAD complex, preventing the activation of cell proliferation genes. When Prdm16 is lost, the SMAD complex relocates to nearby genomic regions, leading to abnormal upregulation of BMP target genes. This function of PRDM16 is also required for the specification of choroid plexus (ChP) epithelial cells. Through a single-cell resolution fluorescent in situ approach, we have observed that genes co-repressed by SMAD and PRDM16, such as Wnt7b and several cell cycle regulators, become overexpressed in Prdm16 mutant ChP. Our findings elucidate a mechanism through which SMAD4 and pSMAD1/5/8 repress gene expression. Moreover, our study suggests a regulatory circuit composed of BMP and Wnt signaling, along with PRDM16, in controlling stem cell behaviors. Overall design: To identify BMP and PRDM16 target genes in primary NSCs, we perfomed ChIP-seq for SMAD4, pSMAD1/5/8 and SMAD3 and cut &tag for PRDM16. Cells treated with BMP4 are controled by cells without BMP4. IgG samples in ChIP-seq serve as negative controls, and Input as normalization controls. To measure transcirptional activation status, we perfomed cut&tag for H3K4me3 in Prdm16_expressing, Prdm16_KO cells as well as those treated with BMP4