Wada Atsushi, Kato Kagayaki, Uwo Makiko F, Yonemura Shigenobu, Hayashi Shigeo
Laboratory for Morphogenetic Signaling, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan.
Dev Biol. 2007 Jan 15;301(2):340-9. doi: 10.1016/j.ydbio.2006.09.020. Epub 2006 Sep 16.
Dorsal closure in Drosophila embryogenesis involves expansion of the dorsal epidermis, followed by closure of the opposite epidermal edges. This process is driven by contractile force generated by an extraembryonic epithelium covering the yolk syncytium known as the amnioserosa. The secreted signaling molecule Dpp is expressed in the leading edge of the dorsal epidermis and is essential for dorsal closure. We found that the outermost row of amnioserosa cells (termed pAS) maintains a tight basolateral cell-cell adhesion interface with the leading edge of dorsal epidermis throughout the dorsal closure process. pAS was subject to altered cell motility in response to Dpp emanating from the dorsal epidermis, and this response was essential for dorsal closure. alphaPS3 and betaPS integrin subunits accumulated in the interface between pAS and dorsal epidermis, and were both required for dorsal closure. Looking at alphaPS3, type I Dpp receptor, and JNK mutants, we found that pAS cell motility was altered and pAS and dorsal epidermis adhesion failed under the mechanical stress of dorsal closure, suggesting that a Dpp-mediated mechanism connects the squamous pAS to the columnar dorsal epidermis to form a single coherent epithelial layer.
果蝇胚胎发育中的背侧闭合涉及背侧表皮的扩展，随后是相对的表皮边缘的闭合。这个过程是由覆盖卵黄合胞体的胚外上皮（称为羊浆膜）产生的收缩力驱动的。分泌的信号分子Dpp在背侧表皮的前缘表达，对背侧闭合至关重要。我们发现羊浆膜细胞的最外层排（称为pAS）在整个背侧闭合过程中与背侧表皮的前缘保持紧密的基底外侧细胞间粘附界面。pAS会响应来自背侧表皮的Dpp而改变细胞运动，这种反应对背侧闭合至关重要。αPS3和βPS整合素亚基在pAS和背侧表皮之间的界面积累，两者都是背侧闭合所必需的。观察αPS3、I型Dpp受体和JNK突变体，我们发现pAS细胞运动发生改变，并且在背侧闭合的机械应力下pAS与背侧表皮的粘附失败，这表明Dpp介导的机制将鳞状的pAS与柱状的背侧表皮连接起来，形成一个单一连贯的上皮层。
