Spermatozoa from mice deficient in Niemann-Pick disease type C2 (NPC2) protein have defective cholesterol content and reduced in vitro fertilising ability
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The cholesterol content of the sperm membrane is regulated during both maturation in the epididymis and capacitation in the female tract, two processes required for the spermatozoa to acquire their fertilising ability. Because Niemann-Pick disease, type C2 (NPC2) protein is one of the most abundant components of the epididymal fluid and contains a functional cholesterol-binding site that can transfer cholesterol between membranes, it has been suggested for years that NPC2 could be involved in the regulation of cholesterol levels in spermatozoa during epididymal maturation. In the present study, western blot and immunohistochemistry analyses demonstrated significant levels of NPC2 in the mouse epididymal epithelium. Epididymal spermatozoa obtained from NPC2 -/- mice were morphologically normal and had normal motility parameters, but had a reduced cholesterol content compared with that of wild-type (WT) spermatozoa, as determined by both biochemical and by flow cytometry analyses. These results suggest that NPC2 could be involved in regulating cholesterol levels in spermatozoa during epididymal maturation. To understand the relevance of epididymal NPC2 for sperm function, the ability of spermatozoa to undergo events influenced by epididymal maturation, such as capacitation and fertilisation, were compared between WT and NPC2 -/- mice. Capacitated NPC2 -/- spermatozoa exhibited defective tyrosine phosphorylation patterns and a reduced ability to fertilise cumulus–oocyte complexes compared with WT spermatozoa, supporting the relevance of mouse epididymal NPC2 for male fertility.
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This work was supported by grants from Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT; 1070622 to SZ; 1070360 to RDM; 3080022 and 11090064 to DB) and a grant from FONDAP (15090007, Center for Genome Regulation (CGR) to SZ). Research in the SCIAN-Lab is supported by FONDECYT (1120579), FONDEF (D07I1019), and Milenio Science Initiative (ICM; P09-015-F).
Quote ItemReproduction, Fertility and Development, 2014, 26, 609–621