| Research Abstract |
This project aims to clarify the mechanism of diversification of species in terms of the genome composition and its transition. For this, it is necessary to develop technologies of genetic modifications for production of animals with new biological functions. One of these technologies is nuclear transplantation
In order to develop nuclear transplantation technology in medaka, cultured cells from the adult fin and six-day-old embryos, or cells from one-day-old embryos (two-somite-stage) were transplanted to unfertilized eggs.
In nuclear transplantation of cultured cells to enucleated unfertilized eggs, no operated individuals developed after the early gastrula stage. In the case using nonenucleated unfertilized eggs, operated individuals survived up to 3 weeks after hatching at the best case, but none of them reached to the adult stage. In these individuals, the number of chromosomes showed mosaicism of N, 2N, and 3N. This abnormality of the chromosome number was possibly due to discordance of the cell cycle between donor and recipient nuclei.
In nuclear transplantation using cells of two-somite-stage embryos, six individuals of 1688 operated eggs hatched (0.4%) and three of them (0.4%) grew to the stage of sexual maturation. Two of these three were triploid and sterile, but one had a diploid nucleus originated from the donor cell and fertile. This is the first report of a diploid and fertile individual obtained by transplantation of somatic nuclei of embryonic cells, although similar results were obtained in experiments using blastula cells (in preparation). Although no individuals developed after the early embryonic stage in nuclear transplantation using enucleated eggs, the present study showed that somatic nuclei of embryonic cells have ability to produce diploid and fertile individuals in nuclear transplantation.
|
