An ultrastructural and immunocytochemical study of a rare genetic sperm tail defect that causes infertility in humans

To characterize and describe the ontogenesis of a rare flagellar defect affecting the whole sperm population of a sterile man.

Case report.

Regional referral center for male infertility in Siena, Italy.

A 28-year-old man with severe asthenozoospermia.

Physical and hormonal assays, semen analysis, and testicular biopsy.

Semen samples and testicular biopsies were analyzed by light and transmission electron microscopy; immunocytochemical study with anti-beta-tubulin and anti-AKAP 82 antibodies was performed to detect the presence and distribution of proteins.

Ultrastructural analysis of ejaculated spermatozoa and testicular biopsy revealed absence of the fibrous sheath in the principal-piece region of the tail. Fibrous sheath-like structures were observed in cytoplasmic residues and residual bodies released by spermatids in the seminiferous epithelium. Other anomalies observed were supplementary axonemes and mitochondrial helix elongation. These features were confirmed by immunocytochemical staining.

This rare sperm tail defect, characterized by absence of the fibrous sheath, presence of supplementary axonemes, and an abnormally elongated midpiece, originates in the seminiferous tubules during spermiogenesis, as detected in testicular biopsy sections. These defects occur in the whole sperm population, and therefore a genetic origin could be suggested.