Mutations in ZP4 Are Associated with Abnormal Zona Pellucida and Female Infertility

BACKGROUND:The zona pellucida (ZP) of human oocytes plays essential protective roles in sperm-egg interactions during fertilisation and embryo development. ZP4-null female rabbits exhibit a thin and irregular ZP, which severely impairs embryo development and fertility. However, the effects of ZP4 defect on human female reproduction remain unknown.METHODS AND RESULTS:We performed whole-exome sequencing in 26 female patients with abnormal (thin and irregular) ZP and identified heterozygous variants in ZP4 (OMIM: 613514) from 3 patients (approximately 11%). No ZP4 variant was found in the 30 control women with proven fertility. We constructed ZP4-mutated plasmids and found that the variants reduced the secretion of ZP4 in vitro. Lower suction pressure facilitated egg retrieval, and intracytoplasmic sperm injection (ICSI) was a desirable treatment for ZP4-mutated patients with abnormal ZP.CONCLUSIONS:We identified ZP4 as a novel gene for human abnormal ZP and found that lower suction pressure and ICSI are efficient treatment strategies.