Evolutionarily conserved boule and dazl identify germ cells of Coilia nasus

Coilia nasus is an endangered fish species in the Yangtze River, and there is urgent need to know the genes related to its reproduction and fertility. The DAZ family including boule, daz and dazl, plays an important role in germ cells development. In this study, the cDNA sequence of boule (Cnbol) and dazl (Cndazl) genes were cloned and their expression patterns were characterized in Coilia nasus. RT-PCR showed that the expression of Cnbol and Cndazl mRNAs was restricted in adult gonads. The section in situ hybridization indicated that the temporospatial expression patterns of Cnbol and Cndazl were significantly different. In the testis, Cnbol was mainly detected in spermatocytes and spermatids, while Cndazl was prominently expressed in s permatogonia. In the ovary, Cnbol and Cndazl were highly expressed in the early stages of oocytes. Interestingly, Cndazl was also concentrated in perinuclear speckle and then localized to the Balbiani body in late stages of oocytes. In addition, Cnbol and Cndazl 3′ UTR can specifically label medaka Primordial Germ Cells (PGCs). According to our results, Cnbol and Cndazl are marker genes of germ cells and may play a vital role in the development and differentiation of germ cells in Coilia nasus.