Background: Cysteine-rich secretory protein 2 (CRISP2) is localized to the human sperm acrosome and tail. It can regulate ryanodine receptors Ca(2+) gating and binds to mitogen-activated protein kinase kinase kinase 11 in the acrosome and gametogenetin 1 (GGN1) in the tail.
Methods and results: In order to test the hypothesis that CRISP2 variations contribute to male infertility, we screened coding and flanking intronic regions in 92 infertile men with asthenozoo- and/or teratozoospermia and 176 control men using denaturing HPLC and sequencing. There were 21 polymorphisms identified, including 13 unreported variations. Three SNPs resulted in amino acid substitutions: L59V, M176I and C196R. All were only present in a heterozygous state and found in fertile men. However, the C196R polymorphism was of particular interest as it resulted in the loss of a strictly conserved cysteine involved in intramolecular disulphide bonding. Screening of an additional 637 infertile men identified 23 heterozygous C196R men to give an overall frequency of 3.6%, compared with 3.4% in control men. The functional significance of the C196R polymorphism was defined using a yeast two-hybrid assay. The C196R substitution resulted in the loss of CRISP2-GGN1 binding.
Conclusions: Although none of the many polymorphisms identified herein showed a significant association with male infertility, functional studies suggested that the C196R polymorphism may compromise CRISP2 function.