Understanding the function and molecular mechanisms of the sperm annulus.
The annulus is a Septin-ring structure located at the junction of the midpiece and the principal piece of mature sperm. It is initially formed in the round spermatids at the very early stages of flagellum assembly, concomitant with nucleus condensation and development of the acrosome. It has been suggested that the annulus acts as a morphological organizer, guiding flagellum assembly during spermiogenesis, and as a diffusion barrier, confining proteins to distinct compartments of the flagellum in mature sperm but the molecular mechanisms underlying such functions are still unknown. Our group initially demonstrated that the sperm specific anion channel SLC26A8 (TAT1) specifically locates to this structure and possibly anchors the Septin polymers to the plasma membrane, thus being required for proper flagellum structure. We also discovered the association of annulus defects in asthenozoospermia and provided an accurate frequency of these defects in human male infertility by analysis of large cohorts of asthenozoospermic individuals.
In line with these findings, our current work combines cell biology, biochemistry, proteomics and mouse genetics with the aim of deciphering the precise functions and molecular mechanisms of the annulus in sperm.
Basic and clinical andrology 25, 10 (2015)
Biological chemistry 392, 799—803 (2011)
Human molecular genetics 16, 1783—1793 (2007)