Female Infertility Due to Zona Pellucida Defect (OOMD1; ZP1-related): Research Report

Target: MONDO:0014342 · OMIM 615774 · ORPHA:404466 · Category: Mendelian Report date: 2026-10-14

How to read the citations. I took the direct quotes marked "abstract quote" from abstracts already cached in this repository's references_cache/, or from the existing draft entry kb/disorders/Female_Infertility_Due_To_Zona_Pellucida_Defect.yaml, which has passed snippet validation. Claims marked [unverified] came from web search or memory and need a PMID lookup with just fetch-reference before they are used as evidence. Some ontology IDs are marked "ID to look up"; I was not able to source those IDs, so I did not write them.

Tooling note. The PubMed, OLS and bgpt MCP connectors in this session need authorization through claude.ai connector settings, and I could not use them here. OMIM returned HTTP 403. Identifiers were confirmed through NCBI MedGen instead.

1. Disease Information

Overview. The disorder is an autosomal recessive form of primary female infertility, with a smaller autosomal dominant arm. It is caused mainly by pathogenic variants in ZP1, which encodes zona pellucida glycoprotein 1. ZP1 cross-links the filaments of the zona pellucida (ZP), the extracellular coat around the oocyte.

Affected women otherwise look reproductively normal: normal karyotype, menarche, menstrual cycles, hormone levels, ovarian reserve and tubal/uterine anatomy. The defect only shows up during ART cycles. Retrieval then yields one of three things: - no oocytes at all (genuine empty follicle syndrome, GEFS); - shrivelled, degenerated oocytes; - mature MII oocytes with no ZP, or a very thin one, which fail conventional IVF.

"Here we describe a form of infertility with an autosomal recessive mode of inheritance, characterized by abnormal eggs that lack a zona pellucida. We identified a homozygous frameshift mutation in ZP1 in six family members." — Huang et al., NEJM 2014, PMID:24670168 (abstract quote)

Identifiers (from NCBI MedGen C4014291, MedGen UID 862728):

Synonyms: oocyte maturation defect 1 (OOMD1); oocyte/zygote/embryo maturation arrest 1 (OZEMA1); ZP1-related empty follicle syndrome; ZP1-related zona pellucida defect; zona-free oocytes, familial.

Nosology caveat. OMIM 615774 and MONDO:0014342 are ZP1-specific. The overlapping ZP2 and ZP3 disorders have their own entries: - ZP3: OOMD3 / OZEMA3, OMIM 617712, MONDO:0021574 - ZP2: OOMD6 / OZEMA6, OMIM 618353, MONDO:0032696

ZP4-related thin-zona infertility currently has no OMIM phenotype entry [verify]. A dismech entry should keep ZP1 as the defining gene and handle ZP2, ZP3 and ZP4 as differentials or a grouping, not lump them in.

Data provenance. All knowledge comes from aggregated case reports and small cohorts, mostly Chinese and North African. There are no registry or EHR-scale data.

2. Etiology

Primary cause. Germline pathogenic ZP1 variants. Inheritance is mostly biallelic (homozygous or compound heterozygous), with a minority of heterozygous variants that appear to act in a dominant-negative way.

Genetic risk factors: - Consanguinity. The index family was a consanguineous Chinese pedigree (PMID:24670168), and the North African founder families are also consanguineous (PMID:42060237). - Founder variant ZP1 c.1097G>A p.(Arg366Gln) in North African populations (PMID:35460069, PMID:42060237).

"The recurrent ZP1 c.1097G > A p.(Arg366Gln) variant contributes to EFS in consanguineous North African families." — PMID:42060237 (abstract quote) - Paternally transmitted heterozygous variants with sex-limited expression, for example ZP1 p.Tyr262Cys (PMID:38966008). Carrier fathers are fertile.

Environmental risk factors: none known. The disorder is fully genetic. Maternal age and stimulation protocol affect ART outcome but do not cause the zona defect.

Protective factors / gene–environment interactions: none described.

Modifiers. Phenotype severity (EFS vs ZP-free MII oocytes) depends on variant type and location. Truncating and splice variants lean toward EFS or degeneration. Some missense variants (for example in the ZP-N1 domain) allow retrieval of ZP-free MII oocytes (PMID:36476320; PMID:42060237). No modifier genes have been identified.

3. Phenotypes

Key quotes:

"All the oocytes from ZP1-associated patients appeared shriveled and dark indicating that the abnormal ZP1 protein induced oocyte death and degeneration." — PMID:35460069

"Sixty-nine mutations of the ZP genes were reported in 87 patients with different clinical phenotypes, including empty follicle syndrome (EFS), ZP-free oocytes (ZFO), ZP-thin oocytes (ZTO), degenerated and immature oocytes. The phenotypes of patients were influenced by the types and location of the mutations." — Zhang et al. 2022 review, PMID:36476320

Severity, progression and quality of life. The phenotype is stable and lifelong. There are no systemic or somatic features. The burden is psychosocial: repeated failed stimulation cycles, cost, and infertility distress. No disease-specific QoL studies exist. Generic FertiQoL data on infertility apply.

4. Genetic / Molecular Information

Causal gene: ZP1 (hgnc:13187; 12 exons; 638-aa type I membrane glycoprotein). Its domains run from N- to C-terminus: signal peptide, ZP-N1 (the cross-linking domain), proline-rich linker, trefoil (P-type) domain, bipartite ZP module (ZP-N and ZP-C), consensus furin cleavage site, transmembrane domain and cytoplasmic tail.

Variant spectrum.

"A total of 47 ZP1 mutations have been reported in 19 pieces of literature … Mutations are distributed in all 12 exons of ZP1 gene … including 13 nonsense mutations, 16 missense mutations, seven splicing mutations and 11 frameshift mutations" — PMID:36476320

Notable variants (transcript NM_207341):

Classification and frequency. Most variants are reported as pathogenic or likely pathogenic in the original papers. ClinVar curation is sparse and there is no ClinGen gene–disease validity curation [verify via just list-gene-validity/CGGV cache]. Variants are rare or absent in gnomAD. The Arg366Gln carrier frequency in North African populations has not been formally estimated.

Origin and function. All variants are germline. The functional consequence is loss of function: truncation, absent secretion, or loss of ZP1-N1 dimerization. Some heterozygous missense and frameshift alleles are proposed to act dominant-negatively, by trapping wild-type ZP2, ZP3 and ZP4 inside the cell (PMID:24670168; PMID:33272616; PMID:32573113). Strictly, heterozygous causality rests on a few families and in-vitro data, so treat it as moderate evidence.

Related ZP genes (differential/allelic group): - ZP3, heterozygous p.Ala134Thr. Autosomal dominant EFS with paternal transmission (Chen et al., AJHG 2017, PMID:28886344 [verify]). A homozygous ZP3 EFS variant has also been reported (Front Genet 2023, PMC10613883). - ZP2. Biallelic variants cause a thin ZP that cannot bind sperm (Dai et al. 2019 [PMID to verify]). A ZP2 loss-of-function variant has been modelled in humans and rats (PMC10244809). - ZP4. Heterozygous loss-of-function variants were found in 3 of 26 women with thin, irregular ZP (about 11%); ICSI pregnancies were achieved (summarized in PMID:36476320). - Combined cohorts:

"We identified zona pellucida (ZP) gene variants in 18 individuals, which included 20 variants in the ZP1 gene, two variants in the ZP2 gene, and one previously reported recurrent variant in the ZP3 gene. The women carrying ZP variants constituted 51.43% of the GEFS cohort." — PMID:33272616

Epigenetics and chromosomal abnormalities: none reported. Karyotype is normal (46,XX).

5. Environmental Information

Not applicable. No toxin, lifestyle or infectious contribution is known. Note that acquired, iatrogenic "false" EFS (for example from a faulty hCG trigger) is a non-genetic phenocopy and has to be excluded clinically (see §10).

6. Mechanism / Pathophysiology

Ordered causal chain

1. Germline ZP1 variant: truncating, splice, or missense in ZP-N1, trefoil or ZP module.
2. This leads to loss of secreted ZP1. Mutant ZP1 is misfolded or truncated and is retained in the oocyte cytoplasm / ER instead of being secreted (shown in HeLa, CHO and 293T cells, and in rat oocytes).

   "secretion of hZP1Mut is completely abolished" — PMID:31300655 (in vitro)

3. Branch A (mainly truncating and dominant-negative alleles). Retained mutant ZP1 binds and co-sequesters wild-type ZP3 and ZP4, and possibly ZP2, inside the cell, so they cannot be exported.

   "the aberrant ZP1 results in the sequestration of ZP3 in the cytoplasm, thereby preventing the formation of the zona pellucida around the oocyte." — PMID:24670168 (in vitro)

Branch B (ZP-N1 missense alleles). ZP1 is secreted but cannot form the disulfide-bonded ZP1-N1 homodimer, so ZP2/ZP3/ZP4 filaments are not cross-linked. Human ZP4 cannot substitute.

"W83R … significantly reduces its ability to form disulphide-bonded homodimers … the mutation leads to lack of the ZP by hindering human ZP filament cross-linking." — PMID:31300655 (in vitro, structural) 4. Both branches result in failed ZP matrix assembly or maintenance. The ZP is absent, very thin, or fragile around growing oocytes. Human ovarian histology shows a thin, ZP1-lacking ZP in preantral follicles (PMID:31734689; one case). 5. Branch point at the antral transition. - 5a. If the matrix is lost or unstable in antral follicles, cumulus–oocyte complex (COC) organization and transzonal oocyte–granulosa communication fail. [Partly inferred] Human histology supports the COC defect (PMID:31734689). The mechanism through communication loss is hypothesized (PMID:36476320). In macaques, ZP1 loss causes oxidative stress, SOD2 downregulation, mitochondrial swelling and autophagy (PMID:40923306; model organism). - 5a → 6a. These changes lead to oocyte degeneration in the follicle, or to fragile oocytes that rupture during aspiration. Clinically this is GEFS or degenerated oocytes. - 5b. If oocytes survive to MII, they lack the ZP sperm-binding matrix. ZP2-N terminus binding, the ZP-induced acrosome reaction, and the zona block to polyspermy are all missing. - 5b → 6b. This leads to fertilization failure in conventional IVF. ICSI bypasses it (§12). 6. Clinical endpoint: primary female infertility (obligate).

Upstream vs downstream. Steps 1–3 are molecular and oocyte-intrinsic. Step 4 is extracellular matrix. Steps 5–6 are follicular and gamete-level.

Suggested terms: - GO BP (validated in the draft YAML): extracellular matrix assembly GO:0085029; protein secretion GO:0009306; protein retention in ER lumen GO:0006621; ovarian follicle development GO:0001541; oocyte development GO:0048599; female gamete generation GO:0007292. Also worth looking up: "binding of sperm to zona pellucida", "egg coat formation", "acrosome reaction". - GO CC: extracellular matrix GO:0031012; endoplasmic reticulum GO:0005783. Look up "egg coat" for the zona pellucida itself. - GO MF: extracellular matrix structural constituent GO:0005201. - CL: oocyte CL:0000023; primary oocyte CL:0000654; granulosa cell CL:0000501. Look up cumulus cell. - Biochemical: no metabolic or immune involvement. This is a structural ECM glycoprotein defect. - Omics: macaque single-oocyte transcriptomics showed disrupted granulosa–oocyte signalling (PMID:40923306). There are no human omics datasets.

7. Anatomical Structures Affected

• Organ: ovary, UBERON:0000992 (primary; the only organ affected). No secondary organ involvement. Body system: female reproductive.
• Tissue: ovarian follicle (look up the UBERON ID), cumulus oophorus, and the zona pellucida ECM.
• Cells: oocyte, primary oocyte, granulosa/cumulus cells.
• Subcellular: oocyte ER/secretory pathway (retention) and the extracellular egg coat.
• Laterality: bilateral (all oocytes affected).

8. Temporal Development

• Onset: the molecular defect is present from oocyte growth, which is fetal/prepubertal for primordial follicles and pubertal onward for growth. It is clinically silent until adulthood, when infertility is investigated or ART is attempted.
• Course: stable and lifelong. No stages and no remission.
• Critical window: the preantral→antral follicle transition, when the ZP must be assembled and maintained (PMID:31734689).

9. Inheritance and Population

• Inheritance: autosomal recessive (HP:0000007) is the main mode. A minority is autosomal dominant (HP:0000006) with sex-limited expression: male carriers, homozygous or heterozygous, are fertile.

  "The ZP1 variants were inherited in an autosomal recessive pattern; the ZP2 and ZP3 variants were inherited in an autosomal dominant pattern." — PMID:33272616

• Penetrance: complete in homozygous females, as far as reported. Penetrance of heterozygous alleles is uncertain.
• Expressivity: variable (EFS vs degeneration vs ZP-free MII), correlated with genotype.
• Founder effect: p.Arg366Gln in North Africa (Algeria/Tunisia/Morocco [country breakdown to verify]).
• Consanguinity: a major contributor in reported families.
• Prevalence: unknown in the general population; ultra-rare (ORPHA lists no estimate [verify]). In enriched cohorts:
• ZP gene variants in 18/35 (51.4%) of Chinese GEFS/degeneration patients (PMID:33272616);
• homozygous ZP1 p.Arg366Gln in 5/27 (18.5%) of North African oocyte-maturation-defect patients (PMID:35460069);
• a 2025 BJOG retrospective study of 12 Chinese women with EFS or degenerated oocytes found rare ZP variants [PMID to verify].
• Underlying context: GEFS itself is reported in roughly 0.016–0.07% of IVF cycles [verify].
• Sex ratio: female-only phenotype.

10. Diagnostics

• Clinical and laboratory work-up:
• Normal FSH, LH, E2 and AMH; normal antral follicle count; normal follicular growth on ultrasound during stimulation.
• At retrieval: no oocytes, degenerated oocytes, or ZP-free/thin-ZP oocytes, seen under light microscopy (polarized-light ZP imaging can quantify thickness).
• Exclude "false EFS" by confirming adequate serum hCG or LH on trigger day.
• Histology (research only): ZP1 immunostaining of ovarian tissue shows a thin ZP lacking ZP1 (PMID:31734689).
• Genetic testing (definitive). Use whole-exome sequencing, or a female-infertility / oocyte-maturation-defect panel covering ZP1, ZP2, ZP3, ZP4, TUBB8, PATL2, WEE2, PANX1, BTG4, TLE6, NLRP family genes and others.

  "In this cohort of North African OMD patients, whole exome sequencing permitted to diagnose 44% of the patients studied and to identify a new frequent ZP1 variant." — PMID:35460069

Targeted testing for p.Arg366Gln is reasonable in North African patients. Microarray, karyotype, FISH, mtDNA and repeat testing are not relevant beyond confirming 46,XX. - Diagnostic ICSI. A small test ICSI can reveal the embryo-development potential of ZP-free oocytes (PMID:32847637). - NCIT: Genetic Testing NCIT:C15709. LOINC has no disease-specific assay. - Differential diagnosis: - OOMD3 (ZP3; AD) - OOMD6 (ZP2; thin ZP with sperm-binding failure) - ZP4 thin zona - OOMD2 (TUBB8; MI arrest with an intact ZP; PMID:26789871) - PATL2 (GV arrest; PMID:35460069 contrasts it with ZP1) - WEE2 (fertilization failure, intact ZP) - iatrogenic false EFS - diminished ovarian reserve / POI (abnormal AMH and FSH) - Screening: none at population level. Cascade testing of sisters is reasonable. Carrier screening is possible in founder populations but not established.

11. Outcome / Prognosis

• Survival, life expectancy and mortality are not affected. There is no systemic morbidity.
• The outcome is infertility with autologous oocytes. Prognosis depends on genotype and phenotype:

  "Three patients with ZP1 mutations, two with ZP2 mutations, and three with ZP4 mutations had successful pregnancies through Intracytoplasmic sperm injection (ICSI) from ZFO or ZTO." — PMID:36476320

The same review built a pregnancy-prediction model (AUC 0.898) from mutation type and location [verify the figure in the full text]. - Poor-prognosis predictors: biallelic truncating ZP1 variants, EFS, and fully degenerated oocytes. Patients in this group usually need oocyte donation. - Complications: repeated futile stimulation cycles, OHSS risk with re-stimulation, and psychological burden.

12. Treatment

There is no disease-modifying therapy. Management is reproductive.

• Embryo transfer: zona-free embryos are fragile, so blastocyst-stage transfer is preferred.
• Pharmacogenomics, gene/cell/RNA therapies: none. No clinical trials were found on ClinicalTrials.gov for ZP1 [search not exhaustive].
• Experimental idea (not in human use): artificial zona or ZP-substitute matrices.

13. Prevention

• Primary: none. The disease is genetic.
• Secondary: genotype-guided ART planning. Women with prior EFS, degenerated oocytes or ZP-free oocytes should be offered ZP-gene testing before repeat cycles. They should go straight to ICSI rather than IVF, or to donation when the genotype predicts EFS (PMID:32573113; PMID:36476320; 2025 BJOG study).
• Counseling: cascade testing of female siblings, especially in consanguineous or North African families. PGT for future generations is theoretically possible, but no one has reported it and there is little rationale because the phenotype is only infertility.
• Vaccination / public health: not applicable.

14. Other Species / Natural Disease

• OMIA: "Infertility, ZP1-related" in Macaca fascicularis (NCBITaxon:9541), OMIA 003005-9541. This entry records the engineered model (PMID:40923306), not natural disease.
• No naturally occurring ZP1 disease is documented in companion animals or livestock [OMIA search for other species advised].
• Comparative biology: ZP gene composition differs across species, and this explains the phenotypes seen in models:
• humans, macaques and rats have four ZP proteins (ZP1–4);
• in mice, Zp4 is a pseudogene (three proteins);
• birds and fish have different ZP repertoires.

The ZP1-N1 cross-linking cysteine is conserved from chicken to human (PMID:31300655). - Orthologs: mouse Zp1 (MGI), rat Zp1 (RGD), macaque ZP1. Look up the NCBI Gene IDs. - Transmission/zoonosis: not applicable.

15. Model Organisms

• Human–model mismatch. The mouse knockout is milder because mice lack ZP4, and a null allele (unlike a retained truncated protein) does not trap partner ZPs. The rat and macaque are the preferred models. This fits a HUMAN_MODEL_MISMATCH discussion, which the draft YAML already carries.
• Resources: MGI, RGD, IMPC (check for a Zp1 line), OMIA.

Key gaps and cautions for curation

1. Population prevalence: none exists. Record it as unknown and use only cohort-enriched frequencies.
2. Heterozygous ZP1 causality rests on very few families. Mark the AD claim with moderate confidence.
3. The step from ZP loss to degeneration (oocyte–cumulus communication, oxidative stress) is supported only by human hypothesis and one macaque model. Edges for it should carry directness: INDIRECT or MODEL_ORGANISM evidence.
4. HPO IDs for "Absent zona pellucida", empty follicle syndrome and oocyte degeneration need lookup. Do not write them from memory.
5. [unverified] PMIDs for Chen 2017 AJHG (ZP3), Dai 2019 (ZP2), the 2025 BJOG cohort, and Rankin's Zp2/Zp3 knockouts need confirmation with just fetch-reference.
6. Draft YAML check: the existing YAML uses the deprecated percentage prevalence field and updated_date. Migrate both to structured prevalence (measure_type: UNKNOWN / cohort fraction) before PR.

Sources

• Huang HL et al. NEJM 2014, PMID:24670168
• Sun L et al. 2021, PMID:33272616
• Zhang Z et al. 2022 review, PMID:36476320 — PMC9730648
• Loeuillet C et al. 2022, PMID:35460069; North African ZP1 follow-up, PMID:42060237
• Nishio S et al. 2019 (ZP1 cross-linking), PMID:31300655
• Sun Y et al. 2019 (compound heterozygous sisters), PMID:31292994
• Cao Q et al. 2020 (ZP1/ZP3 heterozygous), PMID:32573113
• Dai C et al. 2019 / Zhou Z et al. 2019, PMID:30810869
• Case report, ovarian histology, PMID:31734689
• Diagnostic ICSI case report, PMID:32847637
• ZP1-Y262C, PMID:38966008 — Frontiers Genet 2024
• Rat Zp1 knock-in, PMID:33624742; macaque ZP1, PMID:40923306 — Zool Res PDF, OMIA 003005-9541
• Rankin T et al. 1999 (Zp1-null mouse), PMID:10433913
• Feng R et al. 2016 (TUBB8), PMID:26789871
• NCBI MedGen C4014291
• NORD entry
• ZP3 homozygous EFS case, Front Genet 2023
• ZP2 loss of function in humans and rats
• BJOG 2025 ZP variant study (EBSCO record)
• AlphaGalileo summary
• News-Medical, 2026-09-08
• Other search results consulted: PMC7822995, PMC9107549, PMC7642144, PMC7412702, PMC7336750, J Assist Reprod Genet 2022, J Ovarian Res 2025, PMC7492330, eLife ZP, ZP2 IVF failure, GTR ZP1