Institute of Neurobiology and Department of Anatomy and Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, Puerto Rico.
Medical Malacology Department, Theodor Bilharz Research Institute, Giza, Egypt.
J Comp Neurol. 2021 Jun;529(9):2347-2361. doi: 10.1002/cne.25099. Epub 2021 Jan 27.
Freshwater snails of the genus Biomphalaria serve as obligatory hosts for the digenetic trematode Schistosoma mansoni, the causative agent for the most widespread form of intestinal schistosomiasis. Within Biomphalaria, S. mansoni larvae multiply and transform into the cercariae form that can infect humans. Trematode development and proliferation is thought to be facilitated by modifications of host behavior and physiological processes, including a reduction of reproduction known as "parasitic castration." As neuropeptides participate in the control of reproduction across phylogeny, a neural transcriptomics approach was undertaken to identify peptides that could regulate Biomphalaria reproductive physiology. The present study identified a transcript in Biomphalaria alexandrina that encodes a peptide belonging to the gonadotropin-releasing hormone (GnRH) superfamily. The precursor and the predicted mature peptide, pQIHFTPDWGNN-NH (designated Biom-GnRH), share features with peptides identified in other molluscan species, including panpulmonates, opisthobranchs, and cephalopods. An antibody generated against Biom-GnRH labeled neurons in the cerebral, pedal, and visceral ganglia of Biomphalaria glabrata. GnRH-like immunoreactive fiber systems projected to all central ganglia. In the periphery, immunoreactive material was detected in the ovotestis, oviduct, albumen gland, and nidamental gland. As these structures serve crucial roles in the production, transport, nourishment, and encapsulation of eggs, disruption of the GnRH system of Biomphalaria could contribute to reduced reproductive activity in infected snails.
淡水蜗牛属的生物是曼氏血吸虫的必需宿主，曼氏血吸虫是最广泛的肠道血吸虫病的病原体。在淡水蜗牛属中，曼氏血吸虫幼虫繁殖并转化为尾蚴，尾蚴可以感染人类。人们认为，寄生虫的繁殖和增殖是通过改变宿主的行为和生理过程来促进的，包括众所周知的“寄生虫去势”来减少繁殖。由于神经肽参与了整个进化过程中生殖的控制，因此采用神经转录组学方法来鉴定可以调节淡水蜗牛生殖生理学的肽。本研究在亚历山大淡水蜗牛中鉴定出一种编码属于促性腺激素释放激素（GnRH）超家族的肽的转录本。前体和预测的成熟肽 pQIHFTPDWGNN-NH（命名为 Biom-GnRH）与在其他软体动物物种中鉴定出的肽具有相似的特征，包括腹足类、后鳃类和头足类。针对 Biom-GnRH 生成的抗体标记了光滑双脐螺的脑、足和内脏神经节中的神经元。GnRH 样免疫反应纤维系统投射到所有中枢神经节。在外周，在卵黄腺、输卵管、蛋白腺和卵壳腺中检测到免疫反应物质。由于这些结构在卵的产生、运输、营养和包裹中起着至关重要的作用，因此破坏淡水蜗牛的 GnRH 系统可能会导致感染蜗牛的生殖活性降低。
