Sexual plasticity of ovarian germ cells in rainbow trout

Abstract

The sexual plasticity of fish gonads declines after the sex differentiation period; however, information about the plasticity of the germ cells themselves after sex differentiation is limited. Using rainbow trout (Oncorhynchus mykiss), we recently established a novel germ cell transplantation system that provides a unique platform with which to dissect the developmental and cellular mechanisms underlying gametogenesis. Using this technique, we show here that transplanted ovarian germ cells isolated from 6- to 9-month-old donors can colonize sexually undifferentiated embryonic gonads and resume gametogenesis. Ovarian germ cells containing oogonia and early oocytes isolated from female rainbow trout were transplanted into the peritoneal cavities of hatching-stage fry of both sexes and the behavior of the donor cells was observed. The transplanted ovarian germ cells migrated towards the recipient gonads, interacted with embryonic gonadal somatic cells, proliferated rapidly, and eventually differentiated into eggs in female recipients and sperm in male recipients. Furthermore, the donor-derived eggs and sperm obtained from the recipient fish were functional and were able to produce normal offspring. These findings indicate that mitotic germ cells, the oogonia, possess a high level of sexual plasticity.

Sterilization of sterlet Acipenser ruthenus by using knockdown agent, antisense morpholino oligonucleotide, against dead end gene

“…This could result in obtaining sperm and eggs of beluga four times faster than usual. Currently, this biotechnology is well developed for teleost (e.g., zebrafish, goldfish, or loach) by single PGC transplantation [2] or spermatogonia (SG) [21,22] and oogonia (OG) [23,24]. Before PGCs can be used for this purpose, their origin first must be determined and the character and migration pathway needs to be defined.…”

Successful production of functional Y eggs derived from spermatogonia transplanted into female recipients and subsequent production of YY supermales in rainbow trout, Oncorhynchus mykiss

“…This is the first report to succeed in producing Y eggs derived from sexually differentiated spermatogonia. These results confirm the high level of sexual bipotency of spermatogonia described by Okutsu et al (2006a), though it is not clear that the plasticity was retained in a cell population among spermatogonia, or re-acquired in somatic microenvironment of the embryonic gonads after transplantation (Okutsu et al, 2006a;Yoshizaki et al, 2010).…”

“…However, the production of Y eggs and subsequent YY supermales has not yet been demonstrated. On the other hand, it has been confirmed that male recipients who received oogonia (XX) transplantation produced donor-derived spermatozoa, 100% of which had the X sex chromosome, and subsequently produced all-female progeny (Yoshizaki et al, 2010). In the present study, we performed progeny tests using eggs derived from transplanted spermatogonia to confirm the production of Y eggs and the subsequent production of YY supermales.…”

“…Therefore, in an urgent case in which it is necessary to use F1 and/or F2 generations for stock enhancement, the fish can be genotyped by PCR before their release into the wild to adjust the XX female:XY male ratio to 1:1. Another alternative would be proper selection of spermatogonia (Okutsu et al, 2006a(Okutsu et al, , 2007 and oogonia (Yoshizaki et al, 2010) transplantation techniques for male and female recipients, respectively. This would avoid cross-sex germ cell transplantation that would lead to a temporal sex ratio bias in the following generations.…”

Germline stem cells are critical for sexual fate decision of germ cells

“…Regardless of donor trout sex, germ cells that were transplanted into larva assumed the sexual fate of the recipient gonad 18, 19. We also transplanted GFP‐labelled germ cells isolated from adult testis into the coelomic cavity of larva and found that GFP‐germ cells developed into oocytes (unpublished results).…”