Struhl G
J Embryol Exp Morphol. 1983 Aug;76:297-331.
The product of the extra sex combs+ (esc+) gene is required during embryogenesis for the correct determination of segments in Drosophila. If this product is absent, most segments develop like the normal eighth abdominal segment. Here, I extend previous results (Struhl, 1981a) showing that this phenotype results in large part from indiscriminate expression of the bithorax-complex genes which are normally active only in particular segments of the thorax and abdomen. In addition, I test whether the esc+ gene product is required for the correct expression of other homeotic genes. First, I have examined two genes of the Antennapedia-complex (Sex combs reduced+ and Antennapedia+): I find that both genes are normally required in only some of the body segments, but that in the absence of the esc+ gene product, both appear to function adventitiously in other segments. Second, comparing esc+ and esc- embryos lacking both these genes as well as the bithorax-complex, I find that additional homeotic genes (possibly those normally involved in specifying head segments) appear to be expressed indiscriminately when the esc+ gene product is absent. Finally, I present evidence that the products of the esc+ gene and the Polycomb+ gene (a second gene required for the correct regulation of the bithorax-complex) act independently. On the basis of these results, I propose a tentative outline of the roles and realms of action of all of these genes.
超性梳基因（esc+）的产物在果蝇胚胎发育过程中是正确确定体节所必需的。如果没有这种产物，大多数体节会发育得像正常的第八腹节。在此，我扩展了之前的研究结果（Struhl，1981a），表明这种表型在很大程度上是由于双胸复合体基因的随意表达所致，这些基因通常只在胸部和腹部的特定体节中活跃。此外，我测试了esc+基因产物对于其他同源异型基因的正确表达是否必需。首先，我研究了触角足复合体的两个基因（性梳减少基因+和触角足基因+）：我发现这两个基因通常只在身体的某些体节中起作用，但在没有esc+基因产物的情况下，它们似乎在其他体节中随机发挥作用。其次，比较同时缺失这两个基因以及双胸复合体的esc+和esc-胚胎，我发现当esc+基因产物缺失时，其他同源异型基因（可能是那些通常参与确定头部体节的基因）似乎会随意表达。最后，我提供证据表明esc+基因和多梳基因+（双胸复合体正确调控所需的第二个基因）的产物独立发挥作用。基于这些结果，我提出了所有这些基因的作用和作用范围的初步概述。
