Mathies L D, Kerridge S, Scott M P
Department of Developmental Biology, Howard Hughes Medical Institute, Stanford University School of Medicine, California 94305, USA.
Development. 1994 Oct;120(10):2799-809. doi: 10.1242/dev.120.10.2799.
Homeotic genes control the development of embryonic structure by coordinating the activities of downstream 'target' genes. The identities and functions of target genes must be understood in order to learn how homeotic genes control morphogenesis. Drosophila midgut development is regulated by homeotic genes expressed in the visceral mesoderm, where two of their target genes have been identified. Both encode secreted proteins. The Ultrabithorax (Ubx) homeotic gene activates transcription of the decapentaplegic (dpp) gene, which encodes a TGF beta class protein, while in adjacent mesoderm cells the abdominal-A (abd-A) homeotic gene activates transcription of the wingless (wg) gene, which encodes a Wnt class protein. The homeotic genes Antennapedia (Antp) and Sex combs reduced (Scr) act in more anterior midgut regions. Here we report the identification of another homeotic gene target in the midgut mesoderm, the teashirt (tsh) gene, which encodes a protein with zinc finger motifs. tsh is necessary for proper formation of anterior and central midgut structures. Antp activates tsh in anterior midgut mesoderm. In the central midgut mesoderm Ubx, abd-A, dpp, and wg are required for proper tsh expression. The control of tsh by Ubx and abd-A, and probably also by Antp, is mediated by secreted signaling molecules. By responding to signals as well as localized transcription regulators, the tsh transcription factor is produced in a spatial pattern distinct from any of the homeotic genes.
同源异型基因通过协调下游“靶”基因的活性来控制胚胎结构的发育。为了了解同源异型基因如何控制形态发生，必须了解靶基因的身份和功能。果蝇中肠的发育受在内脏中胚层表达的同源异型基因调控，在那里已经鉴定出了它们的两个靶基因。这两个基因都编码分泌蛋白。超双胸（Ubx）同源异型基因激活了编码TGF-β类蛋白的脱翅蛋白（dpp）基因的转录，而在相邻的中胚层细胞中，腹A（abd-A）同源异型基因激活了编码Wnt类蛋白的无翅（wg）基因的转录。同源异型基因触角足（Antp）和性梳减少（Scr）在更靠前的中肠区域起作用。在这里，我们报告了在中肠中胚层中另一个同源异型基因靶标的鉴定，即茶衫（tsh）基因，它编码一种具有锌指基序的蛋白质。tsh对于前中肠和中中肠结构的正常形成是必需的。Antp在前中肠中胚层中激活tsh。在中中肠中胚层中，Ubx、abd-A、dpp和wg对于tsh的正常表达是必需的。Ubx和abd-A，可能还有Antp对tsh的控制是由分泌的信号分子介导的。通过对信号以及局部转录调节因子做出反应，tsh转录因子以一种与任何同源异型基因都不同的空间模式产生。
