The New Roles of traf6 Gene Involved in the Development of Zebrafish Liver and Gonads

Traf6, an adaptor protein, exhibits non-conventional E3 ubiquitin ligase activity and was well studied as an important factor in immune systems and cancerogenesis. In mice, the traf6-null caused a perinatal death, so that the underlying pathophysiology of traf6-defeciency is still largely unclear in animals. Here, in the present study, a traf6 knockout zebrafish line (traf6(-/-)) was generated and could survive until adulthood, providing a unique opportunity to demonstrate the functions of traf6 gene in animals' organogenesis beyond the mouse model. The body of traf6(-/-) fish was found to be significantly shorter than that of the wildtype (WT). Likewise, a comparative transcriptome analysis showed that 866 transcripts were significantly altered in the traf6-/- liver, mainly involved in the immune system, metabolic pathways, and progesterone-mediated oocyte maturation. Especially, the mRNA expression of the pancreas duodenum homeobox protein 1 (pdx1), glucose-6-phosphatase (g6pcb), and the vitellogenesis genes (vtgs) were significantly decreased in the traf6(-/-) liver. Subsequently, the glucose was found to be accumulated in the traf6(-/-) liver tissues, and the meiotic germ cell was barely detected in traf6(-/-) testis or ovary. The findings of this study firstly implied the pivotal functions of traf6 gene in the liver and gonads' development in fish species.