Fujiwara Hironobu, Hayashi Yoshitaka, Sanzen Noriko, Kobayashi Reiko, Weber Charles N, Emoto Tomomi, Futaki Sugiko, Niwa Hitoshi, Murray Patricia, Edgar David, Sekiguchi Kiyotoshi
Institute for Protein Research, Osaka University, Osaka 565-0871, Japan.
J Biol Chem. 2007 Oct 5;282(40):29701-11. doi: 10.1074/jbc.M611452200. Epub 2007 Aug 9.
Basement membranes (BMs) have been implicated in cell fate determination during development. Embryoid bodies (EBs) derived from mouse embryonic stem cells deficient in the laminin gamma1 chain are incapable of depositing a BM, resulting in failure of primitive ectoderm epithelialization. To elucidate the mechanisms involved in this phenomenon, we compared the gene expression profiles of EBs with or without a BM to identify the genes showing BM-dependent expression. We found that the expressions of marker genes for the epithelial-mesenchymal transition (EMT), including the transcription factor Snai2, were up-regulated in LAMC1(-/-) EBs, whereas restoration of a BM to LAMC1(-/-) EBs suppressed the up-regulation of these genes. Overexpression of Snai2 induced the EMT in control EBs by molecular and morphological criteria, suggesting that suppression of the EMT regulatory genes is involved in BM-dependent epithelialization of primitive ectoderm. Despite the failure of primitive ectoderm epithelialization in BM-deficient EBs, mesodermal differentiation was not compromised, but rather accelerated. Furthermore, at later stages of control EB differentiation, the BM was disrupted at the gastrulation site where mesodermal markers were strongly expressed only in cells that had lost contact with the BM. Taken together, these results indicate that the BM prevents the EMT and precocious differentiation of primitive ectoderm toward mesoderm in EBs, implying that BMs are important for the control of mammalian gastrulation.
基底膜（BMs）在发育过程中的细胞命运决定中发挥了作用。源自缺乏层粘连蛋白γ1链的小鼠胚胎干细胞的胚状体（EBs）无法沉积基底膜，导致原始外胚层上皮化失败。为了阐明这一现象所涉及的机制，我们比较了有或没有基底膜的EBs的基因表达谱，以鉴定显示基底膜依赖性表达的基因。我们发现，包括转录因子Snai2在内的上皮-间质转化（EMT）标记基因的表达在LAMC1（-/-）EBs中上调，而将基底膜恢复到LAMC1（-/-）EBs则抑制了这些基因的上调。根据分子和形态学标准，Snai2的过表达在对照EBs中诱导了EMT，这表明EMT调节基因的抑制参与了原始外胚层的基底膜依赖性上皮化。尽管在缺乏基底膜的EBs中原始外胚层上皮化失败，但中胚层分化并未受到损害，反而加速了。此外，在对照EB分化的后期，基底膜在原肠胚形成部位被破坏，在该部位中胚层标记仅在与基底膜失去接触的细胞中强烈表达。综上所述，这些结果表明基底膜可防止EBs中原始外胚层向中胚层的EMT和早熟分化，这意味着基底膜对哺乳动物原肠胚形成的控制很重要。
