Abstract：
Neuropeptides play essential roles in coordinating reproduction. Egg-laying hormone (ELH) is conserved in genetic sequence and behavioral function across molluscs, where neuronal clusters secrete ELH to modulate and induce egg-laying. Here we investigated ELH in the nudibranch mollusc, Berghia stephanieae. ELH preprohormone gene orthologs, which showed clade-specific differences at the C-terminus of the predicted bioactive peptide, were identified in brain transcriptomes across several nudipleuran species, including B. stephanieae. ELH shares deep homology with the corticotropin-releasing hormone gene family, which has roles broadly in stress response. Injection of synthesized B. stephanieae ELH peptide into mature individuals induced egg-laying. ELH gene expression in the brain and body was mapped using in-situ hybridization chain reaction. Across the adult brain, 300-400 neurons expressed ELH. Twenty-one different cell types were identified in adults, three of which were located unilaterally on the right side, which corresponds to the location of the reproductive organs. Ten cell types were present in pre-reproductive juvenile stages. An asymmetric cluster of approximately 100 small neurons appeared in the right pedal ganglion of late-stage juveniles. Additional neurons in the pleural and pedal ganglia expressed ELH only in adults that were actively laying eggs and sub-adults that were on the verge of doing so, implicating their direct role in reproduction. Outside the brain, ELH was expressed on sensory appendages, including in presumptive sensory neurons. Its widespread expression in the nudibranch B. stephanieae suggests that ELH plays a role beyond reproduction in gastropod molluscs.
摘要：
神经肽在协调生殖中起重要作用。产卵激素（ELH）在软体动物的遗传序列和行为功能上是保守的，神经元簇分泌ELH来调节和诱导产卵。在这里，我们调查了裸分支软体动物中的ELH，BerghiaStephanieae.ELH前激素原基因直系同源物，在预测的生物活性肽的C端显示进化枝特异性差异，在几种Nudipleuran物种的脑转录组中发现，包括B.stephanieae.ELH与促肾上腺皮质激素释放激素基因家族有很深的同源性，在应激反应中起着广泛的作用。向成熟个体中注射合成的假单胞菌ELH肽诱导产卵。使用原位杂交链反应对大脑和身体中的ELH基因表达进行了定位。在成年人的大脑中，300-400个神经元表达ELH。在成人中鉴定出21种不同的细胞类型，其中三个单方面位于右侧，对应于生殖器官的位置。在生殖前幼年阶段存在十种细胞类型。晚期少年的右踏板神经节中出现了大约100个小神经元的不对称簇。胸膜和足神经节中的其他神经元仅在积极产卵的成年人和即将产卵的亚成年人中表达ELH，暗示它们在繁殖中的直接作用。在大脑之外，ELH在感觉器官上表达，包括假定的感觉神经元。它在裸体枝菌中的广泛表达表明，ELH在腹足纲软体动物中起着超越繁殖的作用。
