Joint Study on Inductive Interactions in Development

在这项研究中，我们研究了细胞-细胞粘附在诱导发育过程中的作用。此前，yuge博士发现蛙胚胎16细胞期背侧卵裂球细胞质具有背侧决定活性。gumbiner教授和brieher博士阐明了-catenin在青蛙背腹轴形成中的重要性，gerhart教授的研究小组表明了-catenin作为背侧决定因素的重要性。尤格博士检查了他的背侧决定因子是否是β -连环蛋白，发现他的决定因子与β -连环蛋白不同。他的决定因子和β -连环蛋白位于分裂胚胎的皮层中，卡格拉博士表明，皮层的移植导致次级轴形成的频率非常高。钙粘蛋白是依赖Ca^<2+>的细胞粘附分子，似乎通过吸收游离的β -连环蛋白间接控制轴诱导。为了明确钙粘蛋白在诱导中的作用，Tajima克隆了XB钙粘蛋白cDNA，并构建了两个不同的显性负基因结构。敲除钙粘蛋白基因产物对蛙胚原肠胚形成有影响，而对细胞间黏附的影响最小。这有力地表明，其他粘附分子在早期胚胎发育中是活跃的。野村发现了一种新的人血B型活性糖基磷脂酰肌醇锚定凝集素（pi -凝集素），它对Ca^<2+>依赖性细胞-细胞粘附至关重要。这些蛋白是可溶性蛙皮质颗粒凝集素的膜锚定同源物，它定位于未受精卵的皮质，在受精时阻断多精。因此，新发现的pi -凝集素似乎在早期胚胎粘附中起主要作用，它们的定位强烈表明它与背轴决定因子相互作用。我们的实验室正在进行pi -凝集素的敲除。

In this study, we examined the roles of cell-cell adhesion in inductive processes in development. Previously, Dr.Yuge discovered that the cytoplasm of 16-cell stage dorsal blastomeres of frog embryos has dorsal determinant activity. Prof.Gumbiner and Dr.Brieher clarified the importance of beta-catenin in frog dorsoventral axis formation, and Prof.Gerhart's group showed the importance of beta-catenin as dorsal determinant. Dr.Yuge examined whether his dorsal determinants are beta-catenins or not, and found that his determinants are different from beta-catenins. His determinants and beta-catenins are localized in the cortex of the cleaving embryos, and Dr.Kageura showed that grafting of cortex causes secondary axis formation at a very high frequency. Cadherins that are Ca^<2+> dependent cell-cell adhesion molecules seem to be controlling axis induction indirectly by absorbing free beta-catenins. To clarify the roles of cadherins in induction, Tajima cloned the XB cadherin cDNA and made two different dominant negative gene constructs. Gastrulation of frog embryos was affected by knocking out of cadherin gene products while cell-cell adhesion is least affected. This strongly suggests that other adhesion molecules are active in early embyogenesis. Nomura identified novel human blood group B active glycosylphosphatidyl inositol anchored lectin (Pi-lectin), which are essential for Ca^<2+> dependent cell-cell adhesion. The proteins are membrane anchored homologues of soluble frog cortical granule lectins which are localized in cortex of the unfertilized egg and act for blocking of polyspermy at fertilization. Thus newly discovered Pi-lectin seems to be playing major roles in early embryonic adhesion, and their localization strongly suggests that it is interacting with dorsal axis determinants. The knocking out of the Pi-lectin is being carried out in our laboratory.