Journal
GENETICS IN MEDICINE
Volume 21, Issue 2, Pages 431-440Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/s41436-018-0064-y
Keywords
Fertilization failure; Zona pellucida; ZP2; Causative gene; Exome sequencing
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Funding
- National Key Research and Development Program of China [2016YFC1000200]
- National Natural Science Foundation of China [81222007, 81471510, 81372627]
- Program for New Century Excellent Talents in University [907010003]
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Purpose: The oocyte-borne genetic causes leading to fertilization failure are largely unknown. We aimed to identify novel human pathogenic variants (PV) and genes causing fertilization failure. Methods: We performed exome sequencing for a consanguineous family with a recessive inheritance pattern of female infertility characterized by oocytes with a thin zona pellucida (ZP) and fertilization failure in routine in vitro fertilization. Subsequent PV screening of ZP2 was performed in additional eight unrelated infertile women whose oocytes exhibited abnormal ZP and similar fertilization failure. Expression of ZP proteins was assessed in mutant oocytes by immunostaining, and functional studies of the wild-type and mutant proteins were carried out in CHO-K1 cells. Results: Two homozygous s PV (c.1695-2A>G, and c.1691_1694dup (p.C566Wfs*5), respectively) of ZP2 were identified in the affected women from two unrelated consanguineous families. All oocytes carrying PV were surrounded by a thin ZP that was defective for sperm-binding. Immunostaining indicated a lack of ZP2 protein in the thin ZP. Studies in CHO cells showed that both PV resulted in a truncated ZP2 protein, which might be intracellularly sequestered and prematurely interacted with other ZP proteins. Conclusion: We identified loss-of-function PV of ZP2 causing a structurally abnormal and dysfunctional ZP, resulting in fertilization failure and female infertility.
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