Biozentrum, University of Basel, Klingelbergstrasse 50, CH-4056 Basel, Switzerland.
Dev Biol. 2010 Apr 1;340(1):125-33. doi: 10.1016/j.ydbio.2009.12.038. Epub 2010 Jan 4.
The ems/Emx genes encode homeodomain transcription factors that have conserved actions in anterior embryonic patterning in bilaterian animals ranging from insects to mammals. Recently, genes of the ems/Emx family have been identified in cnidarians raising the possibility that some of their developmental functions might be conserved throughout the Eumetazoa. To determine to what extent functions of a cnidarian ems/Emx protein have been retained across phyla, we carried out cross-phylum rescue expression experiments in which the coral Acropora emx-Am gene was misexpressed in Drosophila ems mutants. Our findings demonstrate that coral emx-Am can substitute for fly ems in embryonic head development and rescue the open head defect and the loss of segmental engrailed expression domains in Drosophila ems mutants. In contrast, the coral emx-Am gene can not substitute for fly ems in embryonic brain development. Even when a hexapeptide motif of the type present in the Drosophila ems gene is inserted into the coral emx-Am gene, rescue of the developmental brain defects in fly ems mutants fails. These findings have implications for understanding the evolutionary origins of head versus brain patterning mechanisms.
ems/Emx 基因编码同源域转录因子，在从昆虫到哺乳动物的两侧对称动物的胚胎前模式形成中具有保守作用。最近，在刺胞动物中鉴定出了 ems/Emx 家族的基因，这增加了它们的一些发育功能可能在整个真后生动物中保守的可能性。为了确定刺胞动物 ems/Emx 蛋白的功能在多大程度上跨越门保留下来，我们进行了跨门拯救表达实验，在该实验中，珊瑚 Acropora emx-Am 基因在果蝇 ems 突变体中异位表达。我们的研究结果表明，珊瑚 emx-Am 可以替代果蝇 ems 在胚胎头部发育中，并挽救果蝇 ems 突变体的头部开放缺陷和节段 engrailed 表达域的缺失。相比之下，珊瑚 emx-Am 基因不能替代果蝇 ems 在胚胎大脑发育中的作用。即使将存在于果蝇 ems 基因中的六肽基序插入到珊瑚 emx-Am 基因中，也无法挽救果蝇 ems 突变体中大脑发育缺陷的拯救。这些发现对于理解头部与大脑模式形成机制的进化起源具有重要意义。
