Novel Heterozygous Mutations in ZP2 Cause Abnormal Zona Pellucida and Female Infertility

Zona pellucida (ZP) which is an extracellular matrix consisting of ZP1, ZP2, ZP3, and ZP4 plays a vital role in oocyte maturity, early embryonic development, and fertilization process. Any alterations of structure or function may lead to the abnormal formation of ZP and female infertility. Two novel heterozygous mutations c.1859G > A (p.Cys620Tyr) and c.1421 T > C (p.Leu474Pro) in ZP2 gene were recognized in three patients from two unrelated families with abnormal ZP and female infertility in this study. The expression constructs carrying wild-type ZP2 gene, c.1859G > A (p.Cys620Tyr) mutant ZP2 gene, and c.1421 T > C (p.Leu474Pro) mutant ZP2 gene were transfected into CHO cells respectively. There was a remarkable decrease in the expression of p.Cys620Tyr mutant protein with western blot. In addition, secretion of p.Leu474Pro mutant protein in the culture medium reduced markedly compared with that of wild-type ZP2 protein. Furthermore, co-immunoprecipitation showed that the p.Leu474Pro mutation affected the interaction between ZP2 and ZP3. Prediction of three-dimensional (3D) structure of the proteins showed that p.Cys620Tyr mutation altered the disulfide bond of ZP2 protein and may affect its function. These findings extend the ranges of mutations of ZP2 gene. Meanwhile, it will be helpful to the precise diagnosis of abnormal ZP.