Expression and developmental regulation of the Hydra-RFamide and Hydra-LWamide preprohormone genes in Hydra: evidence for transient phases of head formation.
Expression and developmental regulation of the Hydra-RFamide and Hydra-LWamide preprohormone genes in Hydra: evidence for transient phases of head formation.
复制标题
水螅中 Hydra-RFamide 和 Hydra-LWamide 前激素原基因的表达和发育调节：头部形成短暂阶段的证据。
DOI：
10.1006/dbio.1998.9150
复制
发表时间：
1999
影响因子：
2.7
通讯作者：
C. Grimmelikhuijzen
中科院分区：
文献类型：
--
作者：
Christian Mitgutsch;Frank Hauser;C. Grimmelikhuijzen
Hydra magnipapillata 具有编码前激素原 A、B 和 C 的三个不同基因，每个基因产生一组特征性的 Hydra-RFamide (Arg-Phe-NH2) 神经肽，以及编码前激素原的第四个基因，该基因产生各种 Hydra-LWamide (Leu-Trp-NH2) 神经肽。使用整体双标记原位杂交技术，我们发现这四个基因中的每一个都在成体水螅外胚层的不同神经元子集中特异性表达。前激素原 A 基因在触手、下口（触手和张口之间的区域）、上胃区域和脚（足部上方的区域）的神经元中表达。前激素B基因仅在下口的神经元中表达，而前激素C基因仅在触手的神经元中表达。 Hydra-LWamide 前激素原基因在位于水螅所有部分的神经元中表达，在触手、下口和基盘（脚）中表达最多。对动物再生头部的研究表明，前原 Hydra-LWamide 基因首先表达，然后是前激素原 A，随后是前激素原 C 和前激素原 B 基因。这一系列事件可以通过基于形态发生素梯度中的位置值的模型来解释。我们的头部再生实验也为头部形成的短暂阶段提供了支持：首先，触手特异性前激素原 C 神经元（通常与小触手芽相关）出现在再生尖端的中心，然后它们被下丘脑特异性前激素 B 神经元取代。因此，再生尖端首先获得触手状外观，然后该尖端发育成下口。在水螅发育中的芽中，触手特异性前激素原 C 神经元和下口特异性前激素原 B 神经元几乎同时出现在其正确位置，但在头部发育的后期阶段，额外的触手特异性前激素 C 神经元在下口中心出现为环，然后再次消失。仅由上皮细胞组成的无神经水螅不表达前激素原 A、B 或 C 或 LWamide 前激素原基因。然而，这些动物具有正常的表型，表明前激素原 A、B 和 C 以及 LWamide 基因对于水螅的基本模式形成并不是必需的。
Hydra magnipapillata has three distinct genes coding for preprohormones A, B, and C, each yielding a characteristic set of Hydra-RFamide (Arg-Phe-NH2) neuropeptides, and a fourth gene coding for a preprohormone that yields various Hydra-LWamide (Leu-Trp-NH2) neuropeptides. Using a whole-mount double-labeling in situ hybridization technique, we found that each of the four genes is specifically expressed in a different subset of neurons in the ectoderm of adult Hydra. The preprohormone A gene is expressed in neurons of the tentacles, hypostome (a region between tentacles and mouth opening), upper gastric region, and peduncle (an area just above the foot). The preprohormone B gene is exclusively expressed in neurons of the hypostome, whereas the preprohormone C gene is exclusively expressed in neurons of the tentacles. The Hydra-LWamide preprohormone gene is expressed in neurons located in all parts of Hydra with maxima in tentacles, hypostome, and basal disk (foot). Studies on animals regenerating a head showed that the prepro-Hydra-LWamide gene is expressed first, followed by the preprohormone A and subsequently the preprohormone C and the preprohormone B genes. This sequence of events could be explained by a model based on positional values in a morphogen gradient. Our head-regeneration experiments also give support for transient phases of head formation: first tentacle-specific preprohormone C neurons (frequently associated with a small tentacle bud) appear at the center of the regenerating tip, which they are then replaced by hypostome-specific preprohormone B neurons. Thus, the regenerating tip first attains a tentacle-like appearance and only later this tip develops into a hypostome. In a developing bud of Hydra, tentacle-specific preprohormone C neurons and hypostome-specific preprohormone B neurons appear about simultaneously in their correct positions, but during a later phase of head development, additional tentacle-specific preprohormone C neurons appear as a ring at the center of the hypostome and then disappear again. Nerve-free Hydra consisting of only epithelial cells do not express the preprohormone A, B, or C or the LWamide preprohormone genes. These animals, however, have a normal phenotype, showing that the preprohormone A, B, and C and the LWamide genes are not essential for the basic pattern formation of Hydra.