Parental imprinting on the mouse X chromosome: effects on the early development of X0, XXY and XXX embryos

Abstract

SummaryTo examine the effects of X-chromosome imprinting during early mouse embryogenesis, we attempted to produce XM0, Xp0, XMXMY, XMXPY and XMXMXP(where XMand Xpstand for the maternally and the paternally derived X chromosome, respectively) making use of mouse strains bearing the translocation Rb(X.2)2Ad and the inversion In(X)1H. Unlike XMXPY embryos, XMXMY and XMXMXPconceptuses suffered from severe growth retardation or abnormal development characterized by deficient extra-embryonic structures at 6.5–7.5 days post coitum (dpc). A cytogenetic study suggested that two XMchromosomes remaining active in certain non-epiblast cells were responsible for the serious developmental abnormality found in these embryos disomic for XM. Although matings involving females heterozygous for Rb(X.2)2Ad hinted at the paucity of XP0 embryos relative to those having the complementary karyotype of XMXMXP, further study of embryos from matings between females heterozygous for In(X)1H and Rb2Ad males did not substantiate this observation. Thus, the extensive peri-implantation loss of XP0 embryos shown by Hunt (1991) may be confined to XO mothers. Taken together, this study failed to reveal a parentally imprinted X-linked gene essential for early mouse embryogenesis other than the one most probably corresponding to the X-chromosome inactivation centre.