Dean Derek, Himes Christopher M, Behrman Emily, Savage Robert M
Williams College, Biology Department, Williamstown, Massachusetts 01267, USA.
Biol Bull. 2009 Oct;217(2):189-201. doi: 10.1086/BBLv217n2p189.
We report the expression of Hunchback (Hb)-like protein during embryonic and larval development in two caenogastropods, Crepidula fornicata and Ilyanassa obsoleta. During the cleavage stages of these species, Hb-like protein is uniformly expressed in micromere and macromere nuclei. At gastrulation, gastropod Hb-like protein is expressed in the surface epithelium that undergoes epiboly. During organogenesis, gastropod Hb-like protein is expressed in the developing ciliated structures associated with feeding and locomotion. We find no detectable gradient or regionalization of Hb-like protein in gastropod embryos or larvae that resembles the graded Hb pattern of expression observed in dipteran insect embryos. Rather we found that the spatiotemporal expression profile of gastropod Hb-like protein is nearly identical to the Hb-like patterns obtained from the polychaete Capitella sp. I and is highly similar to those reported for clitellate annelids. Based upon the comparative data collected from both ecdysozoans and lophotrochozoan lineages, our results support the hypothesis that the role of Hb in anteroposterior patterning is a derived trait specific to arthropods, and that the ancestral function of lophotrochozoan Hb-like protein played a role in the formation of the cleavage-stage blastomeres and the gastrula epithelium and in structures associated with larval feeding and locomotion.
我们报道了驼背（Hb）样蛋白在两种新腹足类动物——有沟帽贝和过时泥蚶胚胎及幼体发育过程中的表达情况。在这些物种的卵裂阶段，Hb样蛋白在小分裂球和大分裂球细胞核中均匀表达。在原肠胚形成期，腹足类Hb样蛋白在进行外包的表面上皮中表达。在器官发生过程中，腹足类Hb样蛋白在与摄食和运动相关的发育中的纤毛结构中表达。我们在腹足类胚胎或幼体中未检测到类似双翅目昆虫胚胎中观察到的分级Hb表达模式的Hb样蛋白梯度或区域化。相反，我们发现腹足类Hb样蛋白的时空表达谱与多毛纲小头虫I型获得的Hb样模式几乎相同，并且与寡毛纲环节动物报道的模式高度相似。基于从蜕皮动物和触手冠动物谱系收集的比较数据，我们的结果支持以下假设：Hb在前后模式形成中的作用是节肢动物特有的衍生特征，触手冠动物Hb样蛋白的祖先功能在卵裂期的卵裂球和原肠胚上皮的形成以及与幼体摄食和运动相关的结构中发挥了作用。
