Heads or tails: cell biological secrets of the spermatozoon revealed.

Abstract

Cryobiology has assumed a central place in the daily practice of human ARTs. And despite the expanding utilization of these basic techniques, especially that of vitrification, it is rare for practitioners of reproductive medicine to look beyond how their patients’ gametes and embryos have fared after the “big chill” other than to query their survival and quality status before the next scheduled procedure. When it comes to the cryobiological procedures presently in widespread use around the world, how many clinicians or embryologists are aware of the scientists who contributed the foundational work in this field, some of the most prominent of whom have passed in recent years? Among them, the late John Critser was a foundingmember of the JARG editorial board when I took this position back in 2009, and his vigilance and acumen provided one of the first reports warning about the detrimental effects of high DMSO concentrations on mammalian oocytes, antedating what has since become the business of oocyte banking much to the chagrin of the scientists who forged ahead developing the very protocols now in use today. Both Stan Liebo and Peter Mazur, who recently passed, were also true pioneers in the field of cryobiology as now practiced in human ARTs. It is our intention at JARG to build on the framework of those scientists whose research careers made possible the translation of solid basic science into clinical platforms at the heart of infertility treatments such as cryobiology, a topic to be covered in a future special issue. And in keeping with our commitment to educate our readership on the basic biological principles governing human reproduction, we take aim this month at the male germ cell and some of the remarkable properties of the nucleus and motility apparatus that are deepening our understanding of the complexities underlying fertilization and the molecular basis of infertility. We begin this issue with a comprehensive treatment of the nano-machine that gets sperm where they need to go—the axoneme. Linck and colleagues trace the historical origins of the sperm’s motility apparatus and review in some detail how the introduction of electron microscopy revealed the axoneme as an extraordinary device designed to power the movement of sperm and cilia (The axoneme: the propulsive engine of spermatozoa and cilia and associated ciliopathies leading to infertility. J Assist Reprod Genet DOI 10.1007/s10815-016-0652-1). In fact, for those of us who have spent decades in the business of medical education, the discovery that patients with Kartagener syndrome shared a distinctive ultrastructural deficit in their axonemes underscoring the chronic respiratory distress and infertility symptoms with which they were afflicted, stands as the singular and most significant case of “structure and function” association that has tingled the minds of many physicians and scientists in early stages of their training. The timeliness of this review is further evidenced by coverage of the emerging class of diseases known as ciliopathies, whose genetic and molecular bases are being uncovered in the context of various tissue and organ system pathologies. In this light, it is awe-inspiring to consider that the several hundred genes (by conservative estimates) whose protein products are believed to be required to build the axoneme (and who knows how many post-transcriptional and post-translational steps will be invoked in this construction project that has yet to be teased apart in a mechanistic way) have truly withstood the Capsule Beyond the daily practice of cryobiology in human and ARTs (pl), glimpses of the sperm’s motility machinery in the finest of details with cryotomography electron microscopy are reminding us of how defocused we have become with new wave technologies that bring our thinking and practice into the realm of guesswork rather than truth.