Perfluorooctanoic acid exposure inhibits round spermatid elongation by impeding ubiquitin–proteasome–mediated chromatin remodeling in mice

Round spermatid elongation represents a pivotal morphological transformation essential for functional sperm formation. The present study investigated how perfluorooctanoic acid (PFOA) disrupts this process. Eight-week-old male ICR mice (n=42, 14 per group) received daily oral gavage of PFOA at doses of 0 (Ctrl group), 1 (P1 group) or 10 (P10 group) mg/kg for 35 days. PFOA exposure dose-dependently reduced epididymal sperm count and elevated the ration of round spermatid to elongated spermatid. Moreover, TPPP2, RhoC and ATG4, several proteins specifically expressed in elongated spermatids, were downregulated. Ultrastructure of the chromatoid body (CB)-a specialized structure in round spermatids participating in spermatid elongation-was impaired, indicating that PFOA inhibits round spermatid elongation. Mechanistically, PFOA disrupted the ubiquitin-proteasome system (UPS) by downregulating testicular E2-conjugating enzyme, E3 ubiquitin ligases, testis-specific α4 subunit PSMA8 and two spermatoproteasome activators. Concurrently, chromatin remodeling was disrupted, as evidenced by reduced replacement of histone variants and attenuated post-translational modifications (PTMs)-particularly acetylation and methylation of histone H3 and H4. Consequently, PFOA decreased protamines (PRMs) levels and impaired disulfide bond formation, thereby inhibiting the histone-to-protamine transition (HPT) and chromatin condensation. Collectively, our data demonstrate that PFOA suppresses round spermatid elongation by impeding ubiquitin-proteasome-mediated chromatin remodeling.