Sperm uptake of taurine during epididymal transit, is speculated to play both an antioxidant and osmoregulatory role. The goal of this study was to investigate the functions of Cysteine dioxygenase (CDO) in male fertility. “Cysteine dioxygenase is a mammalian non-heme iron enzyme that catalyzes the conversion of L-cysteine to cysteine sulfinic acid (cysteine sulfinate) by incorporation of dioxygen,”[1] a critical enzyme for taurine synthesis. It has been observed that the concentrations of “Taurine and hypotaurine, an intermediate in the biosynthesis of taurine, in CDO-/- sperm [is] decreased in the epididymal intraluminal fluid and sperm cytosol.”
“CDO-/- sperm exhibited severe defects in volume regulation, [and] swelling in response to the relatively hypo-osmotic conditions found in the female reproductive tract.” The epididymis is a highly complex organ, with multiple histological zones and cell types that together change the composition and functional abilities of sperm through poorly understood mechanisms. It is thought that “sperm uptake of taurine during epididymal transit, may play antioxidant or osmoregulatory roles.” In fact, it was observed that “epididymal CDO plays a key role in post-testicular sperm maturation, enabling sperm to osmoregulate as they transition from the male to the female reproductive tract, and provide[s] new understanding of the compartmentalized functions of the epididymis.” A prior “study reported that male CDO−/− mice exhibit idiopathic infertility, prompting investigates [in] the functions of CDO in male fertility.” Examination “of epididymal segments showed that androgen‐dependent CDO expression was highest in the caput epididymidis.” (upper and larger extremity of the epididymis).
Thus, it was concluded that “epididymal CDO plays a key role in post‐testicular sperm maturation, enabling sperm to osmoregulate as they transition from the male to the female reproductive tract, and provide new understanding of the compartmentalized functions of the epididymis as they transition from the male to the female.”
Ref.: Asano A, Roman HB, Hirschberger LL, Ushiyama A, Nelson JL, Hinchman MM, Stipanuk MH, Travis AJ. Cysteine dioxygenase is essential for mouse sperm osmoadaptation and male fertility. The FEBS Journal. 31 March 2018 DOI: 10.1111/febs.14449.
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