Polycomb repressive complex 2 (PRC2) is an epigenetic regulator of gene expression that possesses histone methyltransferase activity. PRC2 tri-methylates lysine 27 of histone 3 proteins (H3K27me3) as a chromatin modification associated with repressed transcription of genes frequently involved in cell proliferation or self-renewal. Loss-of-function mutations in the PRC2 core subunit SUZ12 have been identified in a variety of tumors, including malignant peripheral nerve sheath tumors (MPNSTs). To determine the consequences of SUZ12 loss in the pathogenesis of MPNST and other cancers, we used CRISPR-Cas9 to disrupt the open reading frame of each of two orthologous suz12 genes in zebrafish: suz12a and suz12b. We generated these knockout alleles in the germline of our previously described p53/nf1-deficient zebrafish model of MPNSTs. Loss of suz12 significantly accelerated the onset and increased the penetrance of MPNSTs compared to control zebrafish. Moreover, in suz12-deficient zebrafish, we detected additional types of tumors besides MPNSTs, including leukemia with histological characteristics of lymphoid malignancies, soft tissue sarcoma, and pancreatic adenocarcinoma, which were not detected in p53/nf1-deficient control fish, and are also contained in the human spectrum of SUZ12-deficient malignancies identified in the AACR Genie database. The suz12-knockout tumors displayed reduced or abolished H3K27me3 epigenetic marks and up-regulation of gene sets reported to be targeted by PRC2. Thus, these zebrafish lines with inactivation of suz12 in combination with loss of p53/nf1 provide a model of human MPNSTs and multiple other tumor types, which will be useful for mechanistic studies of molecular pathogenesis and targeted therapy with small molecule inhibitors.
© 2020. Published by The Company of Biologists Ltd.