Species: mouse
Mutation name: None
type: null mutation
fertility: infertile - ovarian defect
Comment: Rankin TL, et al 2001 reported defective zonae pellucidae in Zp2-null mice disrupt folliculogenesis, fertility and development. The mouse zona pellucida is composed of three glycoproteins (ZP1, ZP2 and ZP3), each encoded by a single copy gene, Using targeted mutagenesis in embryonic stem cells, Zp2-null mouse lines have been established, ZP1 and ZP3 proteins continue to be synthesized and form a thin zona matrix in early follicles that is not sustained in pre-ovulatory follicles, The abnormal zona matrix does not affect initial folliculogenesis, but there is a significant decrease in the number of antral stage follicles in ovaries isolated from mice lacking a zona pellucida, Few eggs are detected in the oviduct after stimulation with gonadotropins, and no two-cell embryos are recovered after mating Zp2-null females with normal male mice. The structural defect is more severe than that observed in Zp1-null mice, which have decreased fecundity, but not quite as severe as that observed in Zp3-null mice, which never form a visible zona pellucida and are sterile. Although zona-free oocytes matured and fertilized in vitro can progress to the blastocyst stage, the developmental potential of blastocysts derived from either Zp2- or Zp3-null eggs appears compromised and, after transfer to foster mothers, live births have not been observed. Thus, in addition to its role in fertilization and protection of early embryos, these data are consistent with the zona pellucida maintaining interactions between granulosa cells and oocytes during folliculogenesis that are critical to maximize developmental competence of oocytes.

Species: mouse
Mutation name: None
type: null mutation
fertility: infertile - ovarian defect
Comment: A single domain of the ZP2 zona pellucida protein mediates gamete recognition in mice and humans. Avella MA 2014 et al. The extracellular zona pellucida surrounds ovulated eggs and mediates gamete recognition that is essential for mammalian fertilization. Zonae matrices contain three (mouse) or four (human) glycoproteins (ZP1-4), but which protein binds sperm remains controversial. A defining characteristic of an essential zona ligand is sterility after genetic ablation. We have established transgenic mice expressing human ZP4 that form zonae pellucidae in the absence of mouse or human ZP2. Neither mouse nor human sperm bound to these ovulated eggs, and these female mice were sterile after in vivo insemination or natural mating. The same phenotype was observed with truncated ZP2 that lacks a restricted domain within ZP2(51-149). Chimeric human/mouse ZP2 isoforms expressed in transgenic mice and recombinant peptide bead assays confirmed that this region accounts for the taxon specificity observed in human-mouse gamete recognition. These observations in transgenic mice document that the ZP2(51-149) sperm-binding domain is necessary for human and mouse gamete recognition and penetration through the zona pellucida. /////////////////////////

Species: human
Mutation name:
type: naturally occurring
fertility: infertile - ovarian defect
Comment: Dosage effects of ZP2 and ZP3 heterozygous mutations cause human infertility. Liu W et al. (2017) The zona pellucida (ZP) is an extracellular matrix universally surrounding mammalian eggs, which is essential for oogenesis, fertilization, and pre-implantation embryo development. Here, we identified two novel heritable mutations of ZP2 and ZP3, both occurring in an infertile female patient with ZP-abnormal eggs. Mouse models with the same mutations were generated by CRISPR/Cas9 gene editing system, and oocytes obtained from female mice with either single heterozygous mutation showed approximately half of the normal ZP thickness compared to wild-type oocytes. Importantly, oocytes with both heterozygous mutations showed a much thinner or even missing ZP that could not avoid polyspermy fertilization, following the patient's pedigree. Further analysis confirmed that precursor proteins produced from either mutated ZP2 or ZP3 could not anchor to oocyte membranes. From these, we conclude that ZP mutations have dosage effects which can cause female infertility in humans. Finally, this patient was treated by intracytoplasmic sperm injection (ICSI) with an improved culture system and successfully delivered a healthy baby.//////////////////

Species: human
Mutation name:
type: naturally occurring
fertility: infertile - ovarian defect
Comment: ZP2 pathogenic variants cause in vitro fertilization failure and female infertility. Dai C et al. (2018) 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. 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. 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. We identified loss-of-function PV of ZP2 causing a structurally abnormal and dysfunctional ZP, resulting in fertilization failure and female infertility.//////////////////

Species: rat
Mutation name:
type: null mutation
fertility: infertile - ovarian defect
Comment: Mutation of rat Zp2 causes ROS-mediated oocyte apoptosis. Wang Y et al. (2020) In this study, we investigated a gene-edited (Zp2MT/MT) rat model of infertility caused by the failure to express the zona pellucida glycoprotein 2 (ZP2) due to the significant reduction of mRNA amount. We examined the defects in the zona pellucida (ZP) caused by ZP2 nullification, and the influence of these defects on aspects of oocyte development, including apoptosis and fertilization ability. To investigate the cause of the influence to the oocytes' development, we evaluated the morphology of follicular transzonal projections (TZPs), known as "bridges", which mediate the bidirectional signaling between the oocyte and surrounding granulosa cells, and the level of reactive oxygen species (ROS) in ovulated eggs. Our results showed that two types of ZP defects were generated in the Zp2MT/MT rat, i.e., ZP intact but thinned and ZP cracked (or even absent). The fertilization rate of the ovulated eggs reduced in both types, while increased oocyte apoptosis was observed only in the latter type. Moreover, the increased oocyte apoptosis rate correlated closely with the reduction in follicular TZPs and increased ROS levels in ovulated egg. In conclusion, nullification of rat ZP2 destroyed the integrity of the ZP, impaired the bidirectional signaling between the oocyte and surrounding granulosa cells. Therefore, the resulting infertility likely occurs via elevation of oxidative stress and oocytes apoptosis.//////////////////

Species: human
Mutation name:
type: naturally occurring
fertility: infertile - ovarian defect
Comment: Novel mutations in ZP1 and ZP2 cause primary infertility due to empty follicle syndrome and abnormal zona pellucida. Luo G et al. (2020) Mutations in the zona pellucida glycoprotein genes have been reported to be associated with empty follicle syndrome (EFS) and abnormal zona pellucida (ZP). In this study, we performed genetic analysis in the patients with female infertility due to abnormal zona pellucida and empty follicle syndrome to identify the disease-causing gene mutations in these patients. We characterized three patients from two independent families who had suffered from empty follicle syndrome or abnormal zona pellucida. Whole exome sequencing and Sanger sequencing were used to identify the mutations in the families. Western blot was used to check the expression of wild type and mutant disease genes. We identified two novel mutations in these patients, including a novel compound heterozygous mutation (c.507delC, p. His170fs; c.239 G>A, p. Cys80Tyr and c.241 T>C, p. Tyr81His) in ZP1 gene and a compound mutation in ZP2 gene (c.860_861delTG, p.Val287fs and c.1924 C>T, p.Arg642Ter). Expression of the mutant ZP1 protein (p. Cys80Tyr and p. Tyr81His) is significantly decreased compared with the wild-type ZP1. Other three mutations produce truncated proteins. Our findings expand the mutational spectrum of ZP1 and ZP2 genes associated with EFS and abnormal oocytes and provide new support for the genetic diagnosis of female infertility.//////////////////

Species: human
Mutation name:
type: naturally occurring
fertility: infertile - ovarian defect
Comment: A novel homozygous variant in ZP2 causes abnormal zona pellucida formation and female infertility. Sun Y et al. (2021) We aimed to identify pathogenic variants in two infertile sisters in a family with a thin zona pellucida (ZP) phenotype. Whole-exome sequencing was performed in the two affected sisters, and Sanger sequencing was used to confirm the identified variants. The effects of the identified variant were further investigated in mouse oocytes and Chinese hamster ovary (CHO) cells. We identified a novel homozygous frameshift variant in ZP2 (c.1235_1236del, p.Q412Rfs*17) in the two affected individuals. Immunoblotting demonstrated that the variant produced a truncated ZP2 protein that was expressed at low levels in CHO cells. Immunofluorescence in mouse oocytes confirmed the decreased protein level of mutant ZP2, although the subcellular localization was not affected. In addition, immunoprecipitation showed that the pathogenic variant reduced the interaction between ZP2 and ZP3. This study identified a novel pathogenic variant in ZP2 that produces a truncated ZP2 protein. The variant might disrupt the assembly of ZP2-ZP3 dimers, thus resulting in a thin ZP and female infertility.//////////////////