Jamieson R V, Tan S S, Tam P P
Embryology Unit, Children's Medical Research Institute, Wentworthville, New South Wales, 2145, Australia.
Dev Biol. 1998 Sep 1;201(1):13-25. doi: 10.1006/dbio.1998.8972.
About 12-17% of the embryos obtained by mating mice carrying the In(X)1H or Paf mutations are of the 39,X (X0) genotype. Depending on the mutant mice used for mating, the monosomic X chromosome can be inherited from the paternal (XP) or the maternal (XM) parent. The XP0 embryos display developmental retardation at gastrulation and early organogenesis. XP0 embryos also display poor development of the ectoplacental cone, which is significantly smaller in size and contains fewer trophoblasts than XX siblings. In contrast, XM0 embryos develop normally and are indistinguishable from XX littermates. In both types of X0 embryos, an X-linked lacZ transgene is expressed in nearly all cells in both the embryonic and the extraembryonic tissues, suggesting that X inactivation does not occur when only one X is present. Of particular significance is the maintenance of an active XP chromosome in the extraembryonic tissues where normally the paternal X chromosome is preferentially inactivated in XX embryos. The differential impact of the inheritance of X chromosomes from different parents on the development of the X0 embryos raises the possibility that the XP is less capable than the XM in providing the appropriate dosage of X-linked activity that is necessary to support normal development of the embryo and the ectoplacental cone. Alternatively, the development of the XP0 embryo may be compromised by the lack of activity of one or several X-linked genes which are expressed only from the maternal X chromosome. Without the activity of these genes, embryonic development may be curtailed even though all other loci on the XP chromosome are actively transcribed.
通过使携带In(X)1H或Paf突变的小鼠交配获得的胚胎中，约12% - 17%为39,X (X0)基因型。根据用于交配的突变小鼠不同，单体X染色体可从父本（XP）或母本（XM）遗传而来。XP0胚胎在原肠胚形成期和早期器官发生期表现出发育迟缓。XP0胚胎的外胎盘锥发育也较差，其尺寸明显小于XX同胞胚胎，且滋养层细胞数量更少。相比之下，XM0胚胎发育正常，与XX同窝仔无差异。在两种类型的X0胚胎中，X连锁的lacZ转基因在胚胎组织和胚外组织的几乎所有细胞中均有表达，这表明当只有一条X染色体存在时，X染色体失活不会发生。特别值得注意的是，在胚外组织中XP染色体保持活性，而在正常的XX胚胎中，父本X染色体通常优先失活。不同亲本来源的X染色体遗传对X0胚胎发育的不同影响，增加了一种可能性，即XP在提供支持胚胎和外胎盘锥正常发育所需的适当剂量的X连锁活性方面，能力不如XM。或者，XP0胚胎的发育可能因一个或几个仅从母本X染色体表达的X连锁基因缺乏活性而受到损害。没有这些基因的活性，即使XP染色体上的所有其他基因座都在活跃转录，胚胎发育也可能受到抑制。
