Cytoplasmic Rearrangements in Early Amphibian Development

未受精的青蛙卵在其主要的动物-植物轴上呈放射状对称，但受精后的事件导致不同细胞质区域的发育命运完全不同。这种区域特化的最早步骤可能涉及到已经存在于卵子中的成分的重新定位。本项目旨在确定非洲爪蟾早期胚胎发生中这些决定因素可能定位的主要细胞机制，并评估这些定位的发育重要性。在早期胚胎发生期间，将检查两个广泛的深层细胞质重排。这些运动中的第一个发生在第一个细胞周期，似乎是由植物卵黄团的定向移位引起的——一个复杂的卵细胞细胞质向未来的背侧移动。第二次运动是每次早期细胞分裂时沿卵裂沟向皮质下细胞质的广泛浸润。这些重排将在鸡蛋中进行，其中特定区域的蛋黄血小板已被荧光标记，以产生卵细胞质运动的三维图像。这些重排对胚胎体轴的重要性将通过在正常胚胎和实验胚胎中进行比较来评估，实验胚胎以各种方式破坏正常的细胞质重排。一个径向对称的卵如何发育成具有背/腹轴和前/后轴的成虫是发育生物学的一个基本问题。这些轴在发展的早期就被设置好了。这项研究是为了研究导致轴形成的一些非常早期的事件。

The unfertilized frog egg is radially symmetric abut its primary, animal-vegetal axis, but events after fertilization lead to completely different developmental fates for various cytoplasmic regions. The earliest steps in this regional specialization probably involve relocalization of components already present in the egg. The aims of this project are to define the major cellular mechanisms whereby such determinants might be localized in early Xenopus laevis embryogenesis and evaluate the developmental importance of those localizations. Two extensive rearrangements of the deep cytoplasm during early embryogenesis will be examined. The first of these movements occurs during the first cell cycle, and appears to result from the directed translocation of the vegetal yolk mass- a complicated shift of ventral egg cytoplasm toward the prospective dorsal side. the second movement is an extensive ingression of subcortical cytoplasm along cleavage furrows during each early cell division. These rearrangements will be followed in eggs in which yolk platelets in specific regions have been fluorescently labelled, to produce a 3-dimensional picture of egg cytoplasmic movements. The importance of these rearrangements for specification of the embryonic body axis will be evaluated by comparing them in normal and experimental embryos, the latter treated in a variety of ways to disrupt normal cytoplasmic rearrangements. %%% How a radially symmetric egg develops into an adult with a dorsal/ventral and anterior/posterior axis is a fundamental question of developmental biology. These axes are set up very early in development. This study is to examine some of those very early events that lead to axis formation.