Tdrd12 Is Essential for Germ Cell Development and Maintenance in Zebrafish.

The regularity of Piwi-interacting RNA (piRNA) biogenesis is crucial to germline development. Functioning as Piwi-interacting proteins, Tudor domain-related proteins (Tdrds) have been demonstrated to be involved in spermatogenesis and the piRNA pathway. In this study, zebrafish tdrd12 was identified, and the maternal and germ cell-specific expression patterns of zebrafish tdrd12 were observed. Utilizing TALEN (transcription activator-like effector nuclease) techniques, two independent tdrd12 mutant zebrafish lines were generated. Although no defects were found during the generation of the primordial germ cells (PGCs) in the tdrd12 -null fish progenies obtained from the heterozygous tdrd12 mutant parents, all Tdrd12-deficient fish developed into infertile males. The reduced numbers and eventually loss of the germ cells by 35 days post fertilization (dpf) led to masculinization and infertility of the Tdrd12-deficient fish. Meiosis defects of the germ cells in the tdrd12 mutants during the gonad-transitioning period were observed, revealing the indispensable functions of Tdrd12 in gametogenesis. Our studies demonstrated that zebrafish Tdrd12 is essential for germ cell development and maintenance.