ACTL7A Expression and Functional Characteristics of Sperm in Infertile Men: A Comparison Between High and Low DNA...

Male infertility accounts for nearly half of all infertility cases, worldwide, and is frequently associated with molecular abnormalities that cannot be detected by routine semen analysis. Actin-like protein 7A (ACTL7A), a testis-specific actin-related protein essential for spermatogenesis, acrosome integrity, and oocyte activation, has recently emerged as a potential regulator of sperm function. This study aimed to investigate the association between ACTL7A expression and sperm DNA integrity in infertile men.

In this comparative cross-sectional study, sixty men were divided into two groups based on sperm DNA fragmentation index (DFI), measured by the sperm chromatin structure assay (SCSA): low DFI (<20%) and high DFI (>20%). Semen parameters, chromatin integrity (aniline blue, chromomycin A3, toluidine blue), and oxidative stress markers [dihydroethidium (DHE) fluorescence and total antioxidant capacity (TAC)], were evaluated. The expression level of ACTL7A was quantified by quantitative polymerase chain reaction (qPCR) and Western blot, and its subcellular localization was determined by immunofluorescence microscopy.

Men with high DFI exhibited significantly reduced sperm motility, elevated levels of reactive oxygen species (ROS), and markedly compromised sperm chromatin integrity, accompanied by decreased ACTL7A expression (P=0.013). No significant differences in sperm morphology or TAC were observed between the groups. Immunofluorescence localized ACTL7A to the equatorial and acrosomal regions of the sperm head. Notably, ACTL7A protein levels correlated strongly with progressive motility (r=0.82, P=0.012). Consistently, individuals with high sperm DNA damage displayed a pronounced reduction in ACTL7A expression, with RNA levels decreased by ~3.4-fold and protein levels by ~2.2-fold, compared to those with low DNA damage.

ACTL7A may serve as a potential indicator of sperm DNA integrity and motility, warranting further validation as a biomarker.