A Key regulatory protein QRICH2 governing sperm function with profound antioxidant properties, enhancing sperm viability

Infertility poses a global health and social challenge, affecting approximately 15% of couples at childbearing age, with half of the cases attributed to male factors, wherein genetic factors exert a substantial role. In our prior investigation, we identified loss-of-function variants within the gene encoding glutamine-rich protein 2 (QRICH2) in two consanguineous families, leading to various morphological abnormalities in sperm flagella and male infertility. Moreover, our observations in Qrich2 knockout mice revealed a pronounced reduction in spermatozoa count. However, the underlying mechanism remains elusive, prompting further investigation in the current study. By conducting experiments such as Hematoxylin-eosin (HE) staining, immunofluorescence staining, flow cytometry, and single sperm metabolism analysis on the testes and spermatozoa of Qrich2 knockout mice, we found a strong antioxidant capacity mediated by QRICH2 both in vivo and in vitro. Qrich2 knockout led to elevated levels of ROS, consequently inducing DNA damage in spermatids, which in turn triggered increased autophagy and apoptosis, ultimately causing a significant decrease in spermatozoa count. Incubation with the N-terminal purified protein of QRICH2 exhibited potent strong antioxidant activity at the cell and spermatozoa levels in vitro, thereby enhancing spermatozoa viability and motility. Therefore, QRICH2 plays a crucial role in safeguarding spermatids from excessive ROS-induced damage by augmenting antioxidant capacity, thereby promoting spermatozoa survival and improving motility. Furthermore, the N-terminal purified protein of QRICH2 shows promise as an additive for protecting spermatozoa during preservation and cryopreservation.