Clayton L, Hall A, Johnson M H
Department of Anatomy, University of Cambridge, Downing Street, Cambridge, CB2 3DY, United Kingdom.
Dev Biol. 1999 Jan 15;205(2):322-31. doi: 10.1006/dbio.1998.9117.
Polarisation of cells during mouse preimplantation development first occurs within blastomeres at the eight-cell stage, as part of a process called compaction. Cell-cell contact mediated by the cell adhesion molecule uvomorulin (E-cadherin) and the activity of the microfilament cytoskeleton are important in the development of compaction, which is crucial for establishment of trophoblast and pluriblast (inner cell mass) lineages and for subsequent development. Members of the Rho family of p21 GTPases have been shown to regulate the organisation of the actin cytoskeleton and adhesion in other cell types. The potential role of these proteins in compaction was investigated. Inhibition of Rho with Clostridium botulinum C3-transferase disturbed intercellular flattening at compaction and prevented cytocortical microfilament polarisation of eight-cell blastomeres, in contrast to cytochalasin D which inhibited only adhesion. Microinjection of a constitutively activated recombinant Rho protein into four-cell blastomeres induced cortical microfilament disruption and apical displacement of nuclei associated with polarised clustering of microtubules. Interblastomere adhesion was reduced and E-cadherin was aberrently clustered at remaining cell-cell contacts. Similarly, activated Cdc42 protein induced nuclear displacement with additional cytoplasmic actin bundle formation between nucleus and cell-cell contacts. The effects produced by both of the activated GTPase proteins are indicative of prematurely induced but aberrently organised polarity. These results suggest that Rho family GTPases are involved in the polarisation of early mouse blastomeres.
在小鼠植入前发育过程中，细胞极化首先发生在八细胞期的卵裂球内，这是称为致密化过程的一部分。由细胞粘附分子桥粒芯蛋白（E-钙粘蛋白）介导的细胞间接触以及微丝细胞骨架的活性在致密化过程中很重要，致密化对于滋养层和多能胚层（内细胞团）谱系的建立以及随后的发育至关重要。已表明p21 GTP酶的Rho家族成员可调节其他细胞类型中肌动蛋白细胞骨架的组织和粘附。研究了这些蛋白质在致密化中的潜在作用。与仅抑制粘附的细胞松弛素D相反，用肉毒杆菌C3转移酶抑制Rho会干扰致密化时的细胞间扁平化，并阻止八细胞卵裂球的细胞皮质微丝极化。将组成型激活的重组Rho蛋白显微注射到四细胞卵裂球中会诱导皮质微丝破坏以及与微管极化聚集相关的细胞核顶端移位。卵裂球间粘附减少，E-钙粘蛋白在剩余的细胞间接触处异常聚集。同样，激活的Cdc42蛋白诱导核移位，并在细胞核与细胞间接触之间形成额外的细胞质肌动蛋白束。两种激活的GTP酶蛋白产生的作用表明极性过早诱导但组织异常。这些结果表明，Rho家族GTP酶参与早期小鼠卵裂球的极化。
