Watts J L, Morton D G, Bestman J, Kemphues K J
Section of Genetics and Development, Cornell University, Ithaca, New York 14853, USA.
Development. 2000 Apr;127(7):1467-75. doi: 10.1242/dev.127.7.1467.
During the first cell cycle of Caenorhabditis elegans embryogenesis, asymmetries are established that are essential for determining the subsequent developmental fates of the daughter cells. The maternally expressed par genes are required for establishing this polarity. The products of several of the par genes have been found to be themselves asymmetrically distributed in the first cell cycle. We have identified the par-4 gene of C. elegans, and find that it encodes a putative serine-threonine kinase with similarity to a human kinase associated with Peutz-Jeghers Syndrome, LKB1 (STK11), and a Xenopus egg and embryo kinase, XEEK1. Several strong par-4 mutant alleles are missense mutations that alter conserved residues within the kinase domain, suggesting that kinase activity is essential for PAR-4 function. We find that the PAR-4 protein is present in the gonads, oocytes and early embryos of C. elegans, and is both cytoplasmically and cortically distributed. The cortical distribution begins at the late 1-cell stage, is more pronounced at the 2- and 4-cell stages and is reduced at late stages of embryonic development. We find no asymmetry in the distribution of PAR-4 protein in C. elegans embryos. The distribution of PAR-4 protein in early embryos is unaffected by mutations in the other par genes.
在秀丽隐杆线虫胚胎发育的第一个细胞周期中，会建立起一些不对称性，这些不对称性对于决定子细胞随后的发育命运至关重要。母源表达的par基因对于建立这种极性是必需的。已发现几个par基因的产物在第一个细胞周期中自身呈不对称分布。我们鉴定出了秀丽隐杆线虫的par-4基因，发现它编码一种假定的丝氨酸 - 苏氨酸激酶，与一种与黑斑息肉综合征相关的人类激酶LKB1（STK11）以及一种非洲爪蟾卵和胚胎激酶XEEK1具有相似性。几个强par-4突变等位基因是错义突变，改变了激酶结构域内的保守残基，这表明激酶活性对于PAR-4的功能至关重要。我们发现PAR-4蛋白存在于秀丽隐杆线虫的性腺、卵母细胞和早期胚胎中，并且在细胞质和皮层均有分布。皮层分布始于1细胞后期，在2细胞和4细胞阶段更为明显，在胚胎发育后期减少。我们发现在秀丽隐杆线虫胚胎中PAR-4蛋白的分布没有不对称性。早期胚胎中PAR-4蛋白的分布不受其他par基因突变的影响。
