Development of tools for site-directed analysis of gene function

组蛋白伴侣Rbbp4是多种染色质重塑复合物的组成部分

The histone chaperone Rbbp4 is a component of multiple chromatin remodeling complexes involved in cellular identity, plasticity, and reprogramming (Cheloufi and Hochedlinger, 2017; Clemot et al., 2018; Conway et al., 2015). Rbbp4 also plays a significant role in cell cycle control as a component of the MuvB complex that regulates cell cycle gene expression. Together with transcription factors B-Myb and FoxM1, the MuvB complex controls the timing of gene expression in G1/S (growth and DNA synthesis) and G2/M (mitosis) that allows progression through the cell cycle (Fischer and Muller, 2017). We previously demonstrated in a zebrafish model of rb1 defective embryonal brain tumors that rbbp4 is elevated more than 10-fold, and we showed that in rbbp4 mutant embryos neural progenitors undergo tp53-dependent apoptosis (Schultz et al., 2018). These results indicate inhibition of Rbbp4 may block the proliferation and survival of brain cancer cells by activating cell cycle arrest through the Tp53 programmed cell death pathway (Engeland, 2018). However, while most malignant human brain cancers show elevated Rbbp4 expression (Schultz, Kool, McGrail unpublished results), many also harbor inactivating mutations in Tp53. A deeper understanding of the mechanism by which Rbbp4 contributes to neural progenitor cell cycle progression may lead to new targets, that in combination with Rbbp4 inhibitors, lead to brain tumor cell death. To address this, we propose to apply our innovative CRISPR/Cas9 targeted integration strategy to generate novel proneural cell cycle reporter and foxm1 conditional gene inactivation zebrafish lines. These will allow us to examine how Rbbp4 and FoxM1 cooperate specifically in neural progenitor cell cycle progression during brain development. The results will yield new insight into neural progenitor cell cycle control and how its dysregulation drives unregulated proliferation of brain tumor cells.