Michelson A M
Department of Medicine, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, MA 02115, USA.
Development. 1994 Apr;120(4):755-68. doi: 10.1242/dev.120.4.755.
Muscle diversification in the Drosophila embryo is manifest in a stereotyped array of myofibers that exhibit distinct segment-specific patterns. Here it is shown that the homeotic genes of the Bithorax complex control the identities of abdominal somatic muscles and their precursors by functioning directly in cells of the mesoderm. Whereas Ultrabithorax (Ubx) and abdominal-A (abd-A) have equivalent functions in promoting the formation of particular muscle precursors in the anterior abdominal segments, Abdominal-B (Abd-B) suppresses the development of these same myogenic cells in the posterior region of the abdomen. When expressed in the same mesodermal cells, however, either UBX or ABD-A can override the inhibitory influence of ABD-B, suggesting that these factors may compete in the regulation of common downstream genes. Furthermore, targeted ectopic expression of Ubx or abd-A indicates that these homeotic genes influence muscle cell fates by autonomous action in mesodermal cells. Muscle identity also appears to be sensitive to the level of UBX in myogenic precursors. Finally, these experiments reveal that homeotic cues specific to both the mesoderm and the ectoderm cooperate to specify the pattern of muscle attachment sites.
果蝇胚胎中的肌肉分化表现为一系列定型的肌纤维，这些肌纤维呈现出独特的节段特异性模式。本文表明，双胸复合体的同源异型基因通过直接在中胚层细胞中发挥作用，控制腹部体壁肌肉及其前体的特性。虽然超双胸（Ubx）和腹-A（abd-A）在促进腹部前部特定肌肉前体的形成方面具有等效功能，但腹-B（Abd-B）抑制腹部后部相同肌源性细胞的发育。然而，当在相同的中胚层细胞中表达时，UBX或ABD-A都可以克服ABD-B的抑制作用，这表明这些因子可能在共同下游基因的调控中相互竞争。此外，Ubx或abd-A的靶向异位表达表明，这些同源异型基因通过在中胚层细胞中的自主作用影响肌肉细胞命运。肌肉特性似乎也对肌源性前体中UBX的水平敏感。最后，这些实验表明，中胚层和外胚层特有的同源异型信号共同作用，确定肌肉附着位点的模式。
