Super-fast generation of all-X sperm grass carp by female germline stem cell transplantation
Grass carp (Ctenopharyngodon idellus), the world's largest aquaculture fish species, exhibits superior growth in females compared to males. However, the lengthy sexual maturation period of four to five years poses a significant obstacle to the genetic reproduction and breeding of grass carp. Consequently, classical methods such as gonadogenesis or sex reversal through steroid treatment, employed for breeding all-female grass carp, demand considerable time and effort. In this study, we developed an super-fast breeding strategy for generating all-female grass carp in a total of half a year, using a surrogate production method. We first characterized grass carp female germline stem cells (GSCs) from genetic female juveniles at three months post-fertilization (mpf). The female GSCs with XX chromosomes were then transplanted into germ cell-depleted zebrafish larvae at five days post-fertilization (dpf). The transplanted grass carp XX germ cells underwent rapid spermatogenesis in the zebrafish recipient. At three months after transplantation, all zebrafish recipients had developed into males capable of producing the all-X sperm of the grass carp. By using these sperm to fertilize wildtype grass carp eggs, we successfully produced an all-female grass carp offspring. This groundbreaking achievement highlights the potential of surrogate production in the genetic breeding of valuable fish species, and opens a new avenue for advancing genetic breeding in aquaculture. Overall design: The GSCT (Germline stem cell transplantation), grass carp and zebrafish sperm were applied to RNA-seq analysis to further examine the genetic consistency among them.