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.