Cytogenetic analysis of reconstituted one-cell mouse embryos derived from nuclear transfer of fetal male germ cells.

Abstract

Micromanipulation techniques were used to produce reconstituted one-cell mouse embryos after the fusion of fetal male germ cells 15.5 day post coitum with enucleated secondary oocytes. At this stage of development, male fetal germ cells are arrested at G1 of mitotic interphase. Two distinct populations of germ cells, differing in size and ploidy, were isolated from the genital ridge of a mid-term fetus. Oocytes that had received male germ cells from the population of smaller (mononuclear) germ cells developed as diploid one-cell reconstituted embryos. When the same procedures were used to produce reconstituted one-cell embryos using male fetal germ cells from a population of larger (multinucleate) cells, they exhibited ploidy of either 4x, 6x or 8x at metaphase of the first cell division. Although most reconstituted embryos (90 and 96%) developed to the two-cell stage, the proportion of embryos receiving small germ cells developed to blastocysts was much higher (62%) than that receiving large germ cells (4%). These studies indicate that not all fetal germ cells are diploid before the onset of meiosis and have identified procedures to produce reconstituted embryos from fetal germ cells that do not carry genome or chromosome anomalies.