Burke Robert D, Murray Greg, Rise Matthew, Wang Diana
Departments of Biology and Biochemistry/Microbiology, University of Victoria, Victoria, BC, Canada.
Dev Biol. 2004 Jan 1;265(1):53-60. doi: 10.1016/j.ydbio.2003.09.025.
Eggs of several metazoans have been demonstrated to express integrins; however, their function is unclear. Previous studies have shown that the betaC integrin subunit is expressed on unfertilized sea urchin eggs and proteolytically removed at fertilization. Here we report that the betaC subunit is reexpressed on the egg surface immediately after fertilization. Using morpholino antisense oligonucleotides to block translation, we show that without betaC expression, eggs undergo cleavage resulting in loosely adherent cells that fail to develop beyond a blastula. Without betaC containing integrins, the cortical actin network of the egg does not form, yet contractile rings appear. Coinjection of RNA encoding the betaC or chicken beta1 subunit, but lacking the morpholino target sequence, rescues the cortical actin network and normal embryos result. Coinjection of RNA encoding the betaC subunit lacking the cytoplasmic domain fails to rescue. These studies demonstrate that the cortical actin cytoskeleton is anchored by betaC integrins and contractile ring actin is not. We suggest that one important function of egg integrins is to organize the actin cortex.
几种后生动物的卵已被证明可表达整合素；然而，其功能尚不清楚。先前的研究表明，βC整合素亚基在未受精的海胆卵上表达，并在受精时被蛋白水解去除。在此我们报告，βC亚基在受精后立即在卵表面重新表达。使用吗啉代反义寡核苷酸阻断翻译，我们发现没有βC表达时，卵会发生卵裂，产生松散附着的细胞，这些细胞无法发育到囊胚期之后。没有含βC的整合素，卵的皮质肌动蛋白网络无法形成，但收缩环会出现。共注射编码βC或鸡β1亚基但缺少吗啉代靶序列的RNA，可挽救皮质肌动蛋白网络并产生正常胚胎。共注射编码缺少细胞质结构域的βC亚基的RNA则无法挽救。这些研究表明，皮质肌动蛋白细胞骨架由βC整合素锚定，而收缩环肌动蛋白则不然。我们认为卵整合素的一个重要功能是组织肌动蛋白皮质。
