A Tale of No Tail: Sperm Flagella Loss in Mormyrids

该项目调查了弱电鱼类，特别是mormords保守性状丧失背后的遗传和进化因素。mormords是一组超过200种的物种，以其独特的特征而闻名，包括产生电信号的能力和精子中完全没有鞭毛。研究组最近在mormords中发现了对精子鞭毛形成至关重要的基因的部分缺失突变。该项目在斑马鱼中使用基因编辑技术来测试这种单一突变是否会导致鱼类失去鞭毛，并研究了一种新发现的mormyrid卵的独特形态特征，该特征可能在鞭毛缺失时促进受精。此外，还将测试几种关于mormyrid精子中鞭毛丢失的进化原因的假设，提供基因突变与作用于它们的进化力量之间的联系。通过揭示突变对依赖于纤毛和鞭毛的其他功能系统的影响，该研究也可能为人类纤毛疾病提供新的见解。该项目通过将研究成果整合到本科课程中，并通过培养一名博士后、两名研究生和几名本科生研究员来促进教学和培训。该项目的目的是了解弱电mormyrid鱼类精子中鞭毛缺失的遗传基础。弱电mormyrid鱼类是一组200多个物种，以其众多衍生和新特征而闻名，包括电发生，电接受和极端脑化的进化。有趣的是，mormord也是已知的唯一一种精子上完全没有鞭毛的脊椎动物。研究重点是高度保守的纤毛和鞭毛相关蛋白，该蛋白在精子鞭毛的形成和纤毛运动中起着至关重要的作用；编码这种蛋白质的基因最近被发现在mormords中有部分缺失。通过使用CRISPR/Cas9基因编辑来创建突变斑马鱼，研究人员将确定这种缺失是否会导致鞭毛丢失，以及这种突变对其他纤毛细胞类型的多性后果。此外，该项目将检查mormords中精子-卵子的相互作用，测试精子竞争的证据，并评估精子鞭毛脱落是由选择能量高效的睾丸驱动的假设。对纤毛虫的研究将为独特的脊椎动物交配系统的进化提供重要的见解，也可能对人类原发性纤毛运动障碍的新治疗干预措施产生影响。除了教育和培训方面的影响，该项目还支持EFISH基因组门户网站的延续，这是科学界研究电鱼的一个资源。该项目由BIO-IOS生理机制和生物力学项目以及动物发育机制项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project investigates genetic and evolutionary factors behind the loss of conserved traits in weakly electric fishes, specifically mormyrids. Mormyrids are a group of over 200 species known for unique traits, including the ability to generate electric signals and the complete absence of flagella in their sperm. The research team recently discovered a partial deletion mutation in a gene that is essential for sperm flagella formation in mormyrids. The project uses gene editing in zebrafish to test whether this single mutation results in the loss of flagella in fishes, and investigates a newly discovered unique morphological trait of mormyrid eggs that may facilitate fertilization when flagella are absent. In addition, several hypotheses about the evolutionary causes of flagella loss in mormyrid sperm will be tested, providing a link between genetic mutations and the evolutionary forces that operate on them. By revealing effects of the mutation on other functional systems dependent upon cilia and flagella, the research may also provide novel insight into human ciliary disease. The project promotes teaching and training by integrating research outcomes into an undergraduate course and through training of a post-doctoral fellow, two graduate students, and several undergraduate student researchers.The objective of the project is to understand the genetic basis of the loss of flagella in sperm in weakly electric mormyrid fishes, a group of over 200 species known for their numerous derived and novel traits, including the evolution of electrogenesis, electroreception, and extreme encephalization. Interestingly, mormyrids are also the only known vertebrate group to completely lack flagella on their sperm. The research focuses on a highly conserved cilia- and flagella-related protein which plays a crucial role in the formation of sperm flagella and ciliary motility; the gene coding for this protein was recently discovered to have a partial deletion within mormyrids. By using CRISPR/Cas9 gene editing to create mutant zebrafish, the investigators will determine whether this deletion leads to flagellar loss, and what pleiotropic consequences of this mutation result for other ciliated cell types. Additionally, the project will examine sperm-egg interaction in mormyrids, test for evidence of sperm competition, and assess the hypothesis that sperm flagellar loss is driven by selection for energetically efficient testes. The study of mormyrids will provide important insights into the evolution of a unique vertebrate mating system and may also have implications for novel therapeutic interventions for primary ciliary dyskinesia in humans. In addition to educational and training impacts, the project also supports continuation of the EFISH Genomics Portal, a resource for the scientific community studying electric fishes.This project was co-funded by the BIO-IOS Physiological Mechanisms and Biomechanics Program and the Animal Developmental Mechanisms Program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.