Understanding molecular mechanisms of male fertility and the link to motile cilia

除对人类健康至关重要外，繁殖成功对物种保护以及可持续农业和粮食至关重要。在人类中，精子质量差是一个值得注意的弱点，它可以解释大约一半的不孕症，但人们对它知之甚少。在本研究中，我们提出对男性因素生育的基本基础进行研究，以期为这一研究领域提供新的思路。我们认为，男性特有的运动纤毛在产生健康、可育的精子中起着重要但被忽视的作用。本研究的重点是研究男性生殖能力的新遗传因素，探索精子和纤毛之间的平衡，以发育和释放健康的男性生殖细胞（配子）。纤毛是长在细胞外的毛发状细胞器，在身体的某些特殊部位需要活动的纤毛，例如在我们的气道中，肺部和上呼吸道的纤毛跳动负责粘液流动和病原体清除。运动纤毛的作用，在传出管是独特的男性人类，是知之甚少。传出管是一种小管，它允许睾丸中的精子通过附睾的结构释放到射精管中。精子在睾丸中发育，并通过传出管和附睾进行运输，在此过程中它们经历成熟，精子尾部（鞭毛）的生长使它们具有运动性。只有经过这种运输，精子才能充分发挥其受精能力。在睾丸（精管）中，男性生殖细胞经过几个步骤成为高度特化的精子。这个过程需要精确定时的基因表达和正确的蛋白质功能，以产生可生育的精子并确保生殖成功。在这个过程中的任何时间点，蛋白质的功能障碍都会导致精子发育受损。因此，我们的目标是描述在不育男性患者的遗传筛选中鉴定的基因的功能，使用苍蝇作为模式生物，因为精子发生是一个保守的过程，苍蝇和人类的蛋白质编码基因相似。我们的实验将帮助我们在进化保守过程中定义遗传学和男性生育能力之间的联系。精子发生的最后阶段包括精子尾巴的形成。活动纤毛和精子尾巴的核心结构几乎相同，但最近发现的蛋白质差异。这些差异将被阐明，并通过精子尾部和/或传出管纤毛功能特征的特定基因突变对男性生育能力的影响。为了做到这一点，我们将检查患者的精子质量和结构，这种疾病是由气道中运动性纤毛突变引起的，因为他们有很高的男性生育能力，但尚未得到很好的表征。不同纤毛类型（气道、传出管）和精子的运动模式不同，因此我们假设它们的运动产生复合物也不同。我们将在纤毛突变的人类精子和纤毛突变的小鼠的传出管纤毛中研究产生动力的动力蛋白的组成和组装。我们推测，输出管纤毛可能通过它们在特殊包（囊泡）中释放的分子与精子相互作用，我们的目标是研究纤毛特异性蛋白质运输被抑制的小鼠突变体中这种串扰的存在和作用。此外，我们将建立细胞培养模型来研究纤毛运动性和其他特征的重要性，以更好地探索它们在可育精子产生中的作用。总的来说，这些实验旨在阐明纤毛相关生育的分子机制，并确定纤毛与精子相关机制对哺乳动物精子成功发育的影响。

Reproductive success is crucial for the preservation of species and sustainable agriculture and food, in addition to being essential to human health. In human populations, poor sperm quality is a noteworthy vulnerability that explains around half of infertility cases but remains very little understood. In this study we propose to study the fundamental basis of male factor fertility in order to shed fresh light in this research area. We propose that there is a major but overlooked role of male-specific motile cilia in the production of healthy, fertile sperm. This proposal is focussed on characterizing new genetic factors in male fertility and exploring the balance of sperm and cilia requirements to develop and release healthy male reproductive cells (gametes). Cilia are hair-like organelles extending outside a cell and motile cilia are required in certain specialised areas of the body, for example in our airways beating of cilia lining the lung and upper airways are responsible for mucus flow and pathogen removal. The role of motile cilia in efferent ducts that are unique to male humans, is poorly understood. The efferent ducts are tubules that allow sperm made in the testis to be released into the ejaculatory duct via a structure called the epididymis. Sperm develop in the testis and are transported through the efferent ducts and epididymis, where they undergo maturation as they proceed, with growth of the sperm tail (flagella) giving them motility. Only after this transport do the sperm reach their full fertilizing capacity. In the testis (seminiferous tubules), male germ cells undergo several steps to become highly specialized spermatozoa. This process requires precisely timed gene expression and correct protein function in order to produce fertile sperm and ensure reproductive success. Malfunction of proteins at any time point during this process results in compromised sperm development. Therefore, we aim to characterize the function of genes identified in genetic screens of infertile male patients, using fly as a model organism because spermatogenesis is a conserved process with similar genes coding for proteins in fly and man. Our experiments will help us to define the link between genetics and male fertility in evolutionary conserved processes. The last phase of spermatogenesis involves formation of the sperm tail. The core structure of the motile cilia and sperm tail is almost identical, but with recently identified protein differences. These differences will be elucidated and the effect of specific genetic mutations on male fertility through sperm tail and/or efferent duct cilia functions characterized. To do this, we will examine the sperm quality and structure in patients a disease caused by mutations of the motile cilia in airways, as they have high male fertility that is not well characterised yet. The motility pattern of different cilia types (airway, efferent duct) and sperm are different and therefore we hypothesize that their motility producing complexes also differ. We will investigate motility-producing dynein composition and assembly, in sperm from humans with cilia mutations and in efferent duct cilia from mice with cilia mutations. We speculate that efferent duct cilia may interact with sperm through molecules they release in special packets (vesicles) and we aim to investigate the presence and role of this crosstalk in mouse mutants where the cilia specific protein transport is inhibited. Furthermore, we will develop a cell culture model to study the importance of cilia motility and other characteristics to better explore their role in production of fertile sperm. Overall, these experiments aim to clarify the molecular mechanisms underlying cilia related fertility and identify the influences of cilia versus sperm related mechanisms in successful sperm development in mammals.