The role of the septin family in spermiogenesis

Abstract

SEPTINS (FULL NAME: Septin; symbol name: SEPT) belong to a family of polymerizing GTP-binding proteins that are required for many cellular functions, including membrane compartmentalization, vesicle trafficking, mitosis and cytoskeletal remodeling. Two of the 14 family members in the mammalian species, Septin12 and 14 are expressed specifically in the testis. In the mouse, knockout of Septin4 and Septin12 leads to male sterility with distinctive sperm pathology (defective annulus or bent neck). In humans, sperm with abnormal expression patterns of SEPT4, 7 and 12 are more prevalent in infertile men. How septin filament is assembled/dissembled and how the SEPT-related complex regulates spermatogenesis still await further investigation.

Figure 1

Working model of SEPT-related complex during mammalian spermatogenesis. (A) We reason that SEPT12-related complex consists of SEPT12, SEPT1, 4, 6 and 7. In the wild-type spermatozoa, SEPT12 coils around the arcosome and is concentrated at the neck of sperm. With the formation of mitochondria, SEPT12 starts to express at the neck and annulus. The SEPT 12 filaments also cover the mitochondrial area. (B) Decreased expression of SEPT12, results in maturation arrest at the spermatid stage, broken acrosome, bent tails, disorganized mitochondria and nuclear DNA damage.