Segmentation gene expression in the housefly Musca domestica.

Drosophila and Musca both belong to the group of higher dipteran flies and show morphologically a very similar early development. However, these two species are evolutionary separated by at least 100 million years. This presents the opportunity for a comparative analysis of segmentation gene expression across a large evolutionary distance in a very similar embryonic background. We have analysed in detail the early expression of the maternal gene bicoid, the gap genes hunchback, Krüppel, knirps and tailless, the pair-rule gene hairy, the segment-polarity gene engrailed and the homoeotic gene Ultrabithorax. We show that the primary expression domains of these genes are conserved, while some secondary expression aspects have diverged. Most notable is the finding of hunchback expression in 11-13 stripes shortly before gastrulation, as well as a delayed expression of terminal domains of various genes. We conclude that the early developmental gene hierarchy, as it has been defined in Drosophila, is evolutionary conserved in Musca domestica.     

Maternal control of vertebrate development before the midblastula transition: mutants from the zebrafish I

Maternal factors control development prior to the activation of the embryonic genome. In vertebrates, little is known about the molecular mechanisms by which maternal factors regulate embryonic development. To understand the processes controlled by maternal factors and identify key genes involved, we embarked on a maternal-effect mutant screen in the zebrafish. We identified 68 maternal-effect mutants. Here we describe 15 mutations in genes controlling processes prior to the midblastula transition, including egg development, blastodisc formation, embryonic polarity, initiation of cell cleavage, and cell division. These mutants exhibit phenotypes not previously observed in zygotic mutant screens. This collection of maternal-effect mutants provides the basis for a molecular genetic analysis of the maternal control of embryogenesis in vertebrates.     

小鼠2-细胞胚胎ATP合成酶6基因特异表达分析及鉴定

合子基因组活化是小鼠胚胎早期发育由细胞质调控向核调控转变的关键 .小鼠合子基因组活化发生在 2 细胞胚胎阶段 ,通过对 2 细胞胚胎阶段特异性表达基因的分析 ,可以从分子水平上揭示早期小鼠胚胎的发育机理 .用DD RTPCR技术 ,从单个小鼠 2 细胞胚胎与成熟卵母细胞 (MII细胞 )中分离了 2个差异片段 ,片段 2同小鼠睾丸中表达的一个未知片段具有高度同源性 .经过cDNA文库构建、筛选 ,分离到其全长cDNA .序列分析结果表明 ,该基因为小鼠ATP合成酶亚单位 6基因 .ATP合成酶亚单位 6基因由线粒体DNA编码 ,与细胞内ATP的合成相关 .小鼠 2 细胞胚胎特异表达的ATP合成酶亚单位 6基因可能与胚胎正常发育相关     

The Effect of a DNA Damaging Agent on Embryonic Cell Cycles of the Cnidarian Hydractinia echinata

The onset of gastrulation at the Mid-Blastula Transition can accompany profound changes in embryonic cell cycles including the introduction of gap phases and the transition from maternal to zygotic control. Studies in Xenopus and Drosophila embryos have also found that cell cycles respond to DNA damage differently before and after MBT (or its equivalent, MZT, in Drosophila). DNA checkpoints are absent in Xenopus cleavage cycles but are acquired during MBT. Drosophila cleavage nuclei enter an abortive mitosis in the presence of DNA damage whereas post-MZT cells delay the entry into mitosis. Despite attributes that render them workhorses of embryonic cell cycle studies, Xenopus and Drosophila are hardly representative of diverse animal forms that exist. To investigate developmental changes in DNA damage responses in a distant phylum, I studied the effect of an alkylating agent, Methyl Methanesulfonate (MMS), on embryos of Hydractinia echinata. Hydractinia embryos are found to differ from Xenopus embryos in the ability to respond to a DNA damaging agent in early cleavage but are similar to Xenopus and Drosophila embryos in acquiring stronger DNA damage responses and greater resistance to killing by MMS after the onset of gastrulation. This represents the first study of DNA damage responses in the phylum Cnidaria.