The Genetics of Cell and Tissue Shape in Drosophila

JACK97-23791肌动蛋白-肌球蛋白细胞骨架在各种情况下控制细胞的形状。肌动蛋白细胞骨架的收缩引起的细胞形状的改变被认为是导致组织形态发生、上皮片内陷、细胞重排和细胞运动的主要原因。肌动蛋白细胞骨架的收缩是由非肌肉肌球蛋白对肌动蛋白细丝的作用引起的。初步结果确定了三种突变，它们阻止了不同组织中的细胞--特别是肾小管上皮细胞和神经系统--呈现出正确的形状。三个突变之一的拉链编码非肌肉肌球蛋白II。另外两个突变RAW和RIBE的产物尚不清楚。肋骨和拉链突变在表型上几乎相同。两者都会导致胚胎缺陷和组织形态异常，这与它们的产物赋予细胞形状的功能一致。RAW的突变导致肋骨和ZIP突变体的表型子集。除了它们表型的显著相似性外，肋骨和ZIP基因的突变是合成致命的，进一步表明这两个产物在相同的过程中发挥作用。这一方案中的实验旨在验证这样一种假设，即非肌肉肌球蛋白II收缩肌动蛋白细胞骨架导致的细胞形状变化需要原始基因和肋骨基因的产物。将对突变胚胎的组织和细胞进行更详细的研究，以检验由突变引起的异常与细胞形状缺陷的预测一致。为了验证有关原始和肋骨产物与非肌肉肌球蛋白之间的功能相互作用的假说，我们将在野生型和突变动物中比较丝状肌动蛋白和非肌肉肌球蛋白在组织和细胞内的分布。此外，其他细胞骨架成分对组织形态的要求将通过评估突变表型和编码它们的基因突变的遗传交互作用来检查。将进行肋骨克隆，以确定其产物与非肌肉肌球蛋白II的序列、细胞位置和生化相互作用。

Jack 97-23791 The actin-myosin cytoskeleton controls the shape of cells in a variety of situations. Changes in the shapes of cells caused by contraction of the actin cytoskeleton are known to be responsible for tissue morphogenesis, invagination of epithelial sheets, cell rearrangement, and cell motility in a variety of organisms. Contraction of the actin cytoskeleton is caused by the action of nonmuscle myosin proteins on actin filaments. Preliminary results identify three mutations that prevent cells in various tissues--especially tubular epithelia and the nervous system--from assuming their proper shape. One of the three mutations, zipper, encodes nonmuscle myosin II. The products of the other two, raw and rib, are unknown. The rib and zip mutations are nearly identical in phenotype. Both cause embryonic defects and abnormalities in tissue morphology consistent with a function of their products in conferring cell shape. Mutations of raw cause a subset of the phenotypes of rib and zip mutants. In addition to the remarkable similarity of their phenotypes, mutations of the rib and zip genes are synthetically lethal, further suggesting that the products function in the same process. Experiments in this proposal are designed to test the hypothesis that the products of the raw and rib genes are required for the cell shape changes caused by the contraction of the actin cytoskeleton by nonmuscle myosin II. Tissues and cells of mutant embryos will be studied in greater detail to test the prediction that the abnormalities caused by the mutations will be consistent with defects in cell shape. In order to test hypotheses regarding the functional interaction between the raw and rib products and nonmuscle myosin, the distribution of filamentous actin and nonmuscle myosin between tissues and within cells will be compared in wild type and mutant animals. In addition, the requirement of other cytoskeletal components on tissue morphology will be examined by assessment of the mutant phenotypes and genetic i nteractions of mutations of the genes that encode them. Cloning of rib will be undertaken in order to characterize the sequence, cellular location, and biochemical interaction of its product with nonmuscle myosin II.