Mullen J R, DiNardo S
Rockefeller University, New York, New York 10021-6399, USA.
Dev Biol. 1995 May;169(1):295-308. doi: 10.1006/dbio.1995.1145.
During Drosophila embryogenesis, a genetic cascade establishes repeating developmental units, the parasegments, along the anterior-posterior axis. Anterior and posterior boundaries of parasegments are defined by narrow stripes of cells expressing the segment polarity genes engrailed and wingless, respectively. Through single and double mutant analysis, we describe genetic interactions regulating the precise activation of engrailed and wingless in alternate parasegments. The pair-rule gene odd-skipped and the segment polarity gene naked are both required to restrict engrailed expression. odd-skipped represses expression of fushi tarazu, a known activator of engrailed. naked prevents activation of engrailed by fushi tarazu, without affecting fushi tarazu expression. engrailed expression is thus limited to narrow stripes of cells at the anterior boundaries of these parasegments. wingless expression is regulated by both odd-skipped and the pair-rule gene paired. odd-skipped represses wingless expression, while paired restricts the domain of expression of odd-skipped. wingless expression is thus allowed in narrow stripes of cells at the posterior boundaries of these parasegments. Accurate expression of engrailed and wingless is also required for cells within each parasegment to assume their proper positional identity. In odd-skipped mutants, the positional identities of particular cells are changed, creating mirror-image duplications of the body pattern. We present a model describing how the altered expression patterns of fushi tarazu, engrailed, and wingless generate the mutant phenotype.
在果蝇胚胎发育过程中，一个基因级联反应沿着前后轴建立起重复的发育单位——副节。副节的前后边界分别由表达节段极性基因 engrailed 和 wingless 的狭窄细胞带所界定。通过单突变和双突变分析，我们描述了调节 engrailed 和 wingless 在交替副节中精确激活的基因相互作用。成对规则基因 odd-skipped 和节段极性基因 naked 都是限制 engrailed 表达所必需的。odd-skipped 抑制 engrailed 的已知激活因子 fushi tarazu 的表达。naked 阻止 fushi tarazu 激活 engrailed，而不影响 fushi tarazu 的表达。因此，engrailed 的表达被限制在这些副节前边界的狭窄细胞带中。wingless 的表达受 odd-skipped 和成对规则基因 paired 的调控。odd-skipped 抑制 wingless 的表达，而成对规则基因 paired 则限制 odd-skipped 的表达域。因此，wingless 的表达在这些副节后边界的狭窄细胞带中得以允许。每个副节内的细胞要确定其正确的位置身份，也需要 engrailed 和 wingless 的精确表达。在 odd-skipped 突变体中，特定细胞 的位置身份发生改变，产生身体模式的镜像重复。我们提出了一个模型，描述了 fushi tarazu、engrailed 和 wingless 的表达模式改变如何产生突变体表型。
