Molecular Mechanism of Ciliogenesis/Spermatogenesis

Dear Colleagues,

Spermatogenesis is a highly specialized physiological process during which male germ cells proliferate, undergo meiosis and differentiate to produce spermatozoa. During this process, germ cells undergo major morphological modifications, including acrosome formation, chromosome condensation and flagellogenesis. The acrosome is a cap-like structure mainly derived from the Golgi apparatus. It contains digestive enzymes that break down the outer membrane of the ovum for normal fertilization. Of the morphological modifications, flagellum formation is the most spectacular. The sperm flagellum acts as a propulsive organelle that allows the sperm cells to reach and penetrate the egg at fertilization. This motility is generated by a microtubule-based cytoskeletal structure that forms the core of the flagellum, called the axoneme. The axonemal structure consists of nine outer double microtubules surrounding a central pair of single microtubules. This structure that has been well conserved through evolution and is also present in cilia on the trachea, oviducts and numerous other tissues. In addition to the axoneme, sperm flagellum comprises additional peri-axonemal structures, allowing this organelle to function differently. Two major transport systems, the intra-manchette transport and intraflagellar transport, are believed to play essentiaol roles in transporting cargo proteins for normal sperm flagella formation. Male germ cells have unique regularatory mechanisms for gene expression, including transcriptional and epigenetic regulation such as DNA methylation. Non-coding RNAs including piRNAs play important roles in normal germ cell development.  Defects in these germ cell-specific structures are responsible of asthenozoospermia and male infertility that could be isolated or associated with ciliopathy. Recent advances in both techniques of high throughput sequencing (HTS) and genome editing have facilitated the increase of our fundamental and clinical knowledge about the function of numerous genes implicated in these disorders. For example, the use of whole exome sequencing these last years led to the discovery of more than 20 genes responsible for multiples morphological abnormalities in sperm flagella (MMAF syndrome), and more than 40 genes have been reported in primary ciliary dyskinesia (PCD). The CRISPR/Cas9 is a complementary technique to HTS that accelerates the production of transgenic animal models to validate the pathogenic effect of the identified variants and to study the function of genes of interest. The main aim of this topic is to elucidate the high complexity of the molecular network underlying the structural organisation and function of such organelles and to explore the molecular pathogeny associated with their disorders which lead to male infertility and/or ciliopathies.

Dr. Zhibing Zhang
Dr. Zine Eddine Kherraf
Prof. Shuiqiao Yuan
Guest Editors

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