Expression of X-linked genes in androgenetic, gynogenetic, and normal mouse preimplantation embryos.

A quantitative RT-PCR approach has been used to examine the expression of a number of X-linked genes during preimplantation development of normal mouse embryos and in androgenetic and gynogenetic mouse embryos. The data reveal moderately reduced expression of the Prps1, Hprt, and Pdha1 mRNAs in androgenetic eight-cell and morula stage embryos, but not in androgenetic blastocysts. Pgk1 mRNA abundance was severely reduced in androgenones at the eight-cell and morula stages and remained reduced, but to a lesser degree, in androgenetic blastocysts. These data indicate that paternally inherited X chromosomes are at least partially repressed in androgenones, as they are in normal XX embryos, and that the degree of this repression is chromosome position-dependent or gene-dependent. Gynogenetic embryos expressed elevated amounts of some mRNAs at the morula and blastocyst stages, indicative of a delay in dosage compensation that may be chromosome position-dependent. The Xist RNA was expressed at a greater abundance in androgenones than in gynogenones at the eight-cell and morula stages, consistent with previous studies. Xist expression was observed in both androgenones and gynogenones at the blastocyst stage. We conclude that the developmental arrest in early androgenones may be, in part, due to reduced expression of essential X-linked genes, particularly those near the X inactivation center, whereas the developmental defects of gynogenones and parthenogenones, by contrast, may be partially due to overexpression of X-linked genes in extraembryonic tissues, possibly those farthest away from the X inactivation center.