Androglobin, a chimeric mammalian globin, is required for male fertility

Abstract

Spermatogenesis is a highly specialised process, involving multiple dedicated pathways and regulatory check-points. Defects ultimately lead to male sub-fertility or sterility, and numerous aspects of mammalian sperm formation remain unknown. The predominant expression of the latest globin family member, androglobin (Adgb) in mammalian testis tissue prompted us to assess its physiological function in spermatogenesis. Adgb knockout mice display male infertility, reduced testis weight, impaired maturation of elongating spermatids, abnormal sperm shape and ultrastructural defects in microtubule and mitochondrial organisation. Epididymal sperm from Adgb knockout animals display multiple flagellar malformations including coiled, bifide or shortened flagella, and erratic acrosomal development. Following immunoprecipitation and mass spectrometry, we could identify septin 10 (Sept10) as interactor of Adgb. The Sept10-Adgb interaction was confirmed both in vivo using testis lysates, and in vitro by reciprocal co-immunoprecipitation experiments. Furthermore, absence of Adgb leads to mislocalisation of Sept10 in sperm, indicating defective manchette and sperm annulus formation. Finally, in vitro data suggest that Adgb contributes to Sept10 proteolysis in a calmodulin (CaM)-dependent manner. Collectively, our results provide evidence that Adgb is essential for murine spermatogenesis and further suggest that interdependence between Adgb and Sept10 is required for sperm head shaping via the manchette and proper flagellum formation.