RB1 and primitive neuroectodermal tumor: In another approach, transcription activator-like effector nuclease (TALEN)-mediated inactivation of tumor suppressor genes, such as cyclin-dependent kinase inhibitor 2A (cdkn2a/b) and retinoblastoma 1 (rb1), in zebrafish resulted in the development of tumors that mimic human MB and primitive neuroectodermal tumors (PNETs) [179].