Subzonal insemination with primary spermatocytes in mouse

摘要

IT is well known that oocytes, in general condition, can be penetrated by sperm rather than round spermatids. In 1993, Ogura injected round spermatid nuclei into hamster oocytes and demonstrated that the spermatid nuclei could transform into pronucleiwith DNA synthesis and that their chromosomes mingled with oocyte chromosomes immediately. In order to avoid the mechanical damage to the oocytes, an alternative method, cell-to-cell fusion, was used. Approximately 20 % -- 40 % and 30 % of round spermatids could be fused with oocytes by electric stimulation in hamster and mouse, respectively. Some of the fused mouse oocytes could develop normally to term. Secondary spermatocyte is 2 N haploid. After injection of a single secondary spermatocyte nucleusinto an oocyte, both the oocyte and spermatocyte chromosomes completed their meiotic divisions, resulting in the formation of a haploid female and male pronuclei, which supported normal embryonic development 24% of the embryos could develop into normal offspring after transfer. Primary spermatocyte is 4 N diploid. Can it participate in syngamy? In 1995, Kimura reported that when the oocyte into which a primary spermatocyte was injected was left unactivated for 2 h, the spermatocyte chromosomes con-densed prematurely. These chromosomes as well as metaphase- II oocyte chromosomes resumed meiosis upon electroactivation, culminating in the formation of two pronuclei, one of which was paternal origin and was diploid or polyploid. On the basis of our previous success in the microfertilization with round spermatids, the behavior and developmental potential of mouse primary spermatocyte nuclei fused into the oocytes are reported in this note.