Kurz H, Zechner U, Orth A, Fundele R
Institute of Anatomy II, Freiburg, Germany.
Anat Embryol (Berl). 1999 Sep;200(3):335-43. doi: 10.1007/s004290050284.
The placenta plays a pivotal role in fetal growth control and is considered a major site of genetic conflict between maternal and paternal genomes within the conceptus and, in addition, the genome of the mother. Accordingly, placental development is a strictly controlled process, and both placental and fetal weights do not vary much in intraspecific crosses of laboratory mice (Mus musculus). In mouse interspecific crosses and backcrosses [(M. musculus x M. spretus) x M. musculus], tremendous variation of placental, but not of fetal weight was observed. We have studied trophoblast cell type distribution and differentiation, and their effect on the associated placentas and fetuses in such backcrosses. Differentiation of spongious trophoblast, but not size of materno-fetal interface, correlated with fetal weight. Giant fetuses were observed only if less than one third of the spongiotrophoblast was formed by glycogen cells. Thus, placental efficiency was inversely related to the amount of glycogen cells. This influence of a trophoblast-derived cell type on fetal growth was not anticipated. We conclude that: (1) glycogen cells are able to negatively modulate fetal growth by an as yet unidentified mechanism; (2) correlation between fetal and placental weights is weak or absent in interspecific hybrids; (3) impaired control over placental and embryonic development in hybrids may contribute to post-mating isolation of species.
胎盘在胎儿生长控制中起关键作用，被认为是受精卵中母本和父本基因组以及母亲基因组之间遗传冲突的主要场所。因此，胎盘发育是一个严格受控的过程，在实验室小鼠（小家鼠）的种内杂交中，胎盘重量和胎儿重量变化不大。在小鼠种间杂交和回交[（小家鼠×西班牙小鼠）×小家鼠]中，观察到胎盘重量有巨大差异，但胎儿重量没有。我们研究了此类回交中滋养层细胞类型分布和分化及其对相关胎盘和胎儿的影响。海绵状滋养层的分化而非母胎界面的大小与胎儿体重相关。仅当不到三分之一的海绵滋养层由糖原细胞形成时才观察到巨大胎儿。因此，胎盘效率与糖原细胞数量呈负相关。滋养层来源的细胞类型对胎儿生长的这种影响是出乎意料的。我们得出以下结论：（1）糖原细胞能够通过一种尚未明确的机制对胎儿生长产生负调节作用；（2）种间杂种中胎儿体重与胎盘重量之间的相关性较弱或不存在；（3）杂种中对胎盘和胚胎发育的控制受损可能有助于物种交配后的隔离。
