Novel WEE2 homozygous mutations c.1346C>T and c.949A>T identified in primary infertile women due to unexplained fertilization failure

The occurrence of unexplained fertilization failure can have profound psychological and financial consequences for couples struggling with infertility, and its pathogenesis remains unclear. Increasing evidence highlights genetic basis of unexplained fertilization failure occurrence. Here, we identified one novel homozygous nonsense mutation (c.949A>T), one novel homozygous missense mutation (c.1346C>T), and three reported homozygous mutations (c.585G>C, c.1006_1007insTA, c.1221G>A) in six unrelated probands, showing similar manifestations of unexplained fertilization failure. This finding expands the spectrum of WEE2 mutations, highlighting the critical role of WEE2 in fertilization process, and provides a basis for the prognostic value of testing for WEE2 mutations in primary infertile couples with unexplained fertilization failure.

Clinical exome sequencing identifies novel compound heterozygous mutations of the WEE2 gene in primary infertile women with fertilization failure

OBJECTIVE

The genetic basis of fertilization failure after intracytoplasmic sperm injection (ICSI) is largely unknown and the aim of this study is to investigate the genetic causes of fertilization failure in primary infertile women.

METHODS

Six affected women diagnosed with infertility and fertilization failure were recruited. The genetically pathogenic factor of their fertilization failures were investigated by clinical exome sequencing. One hundred healthy controls were verified by Sanger sequencing.

RESULTS

Novel compound heterozygous mutations c.625G > T and c.759-2A > G of WEE2 in one affected individual were revealed by clinical exome sequencing. Trios analysis of the mutations represented an autosomal recessive pattern. The nonsense mutation c.625G > T (p.Glu209*) indicated the truncation of the WEE2 protein and c.759-2A > G was predicted to affect the splicing.

CONCLUSIONS

The novel variants extend the spectrum of WEE2 mutations, which promotes the prognostic value of testing for WEE2 mutations in infertile women with fertilization failure.

Novel WEE2 compound heterozygous mutations identified in patients with fertilization failure or poor fertilization

Purpose

To study associations between novel WEE2 mutations and patients with fertilization failure or poor fertilization.

Methods

Thirty-one Chinese patients who underwent treatment with assisted reproductive technology and suffered from repeated (at least two times) total fertilization failure (TFF) or a low fertilization rate were enrolled. Genomic DNA was extracted from patients for whole-exome sequencing. Suspicious mutations were validated by Sanger sequencing. WEE2 protein levels in oocytes from affected patients were examined by immunofluorescence. Disruptive effects of mutations on WEE2 protein stability, subcellular localization, and kinase function were analyzed through western blotting, immunofluorescence, and flow cytometry in HeLa cells.

Results

Three of thirty-one (9.6%) enrolled patients had six compound heterozygous mutations of the WEE2 gene, and three of them were reported here for the first time (c.115_116insT, c.756_758delTGA, and c.C1459T). Oocytes from affected patients showed decreased WEE2 immunofluorescence signals. In vitro experiments showed that the mutant WEE2 gene caused reduced WEE2 protein levels or cellular compartment translocation in HeLa cells, leading to decreased levels of the phosphorylated Cdc2 protein. Compared with the wild-type WEE2 protein, the mutant WEE2 proteins were also found to have different effects on the cell cycle.

Conclusion

Three novel compound heterozygous WEE2 variants were found in patients with pronucleus formation failure. This study provides new evidence that WEE2 mutations result in loss of function, which could result in fertilization failure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10815-021-02285-z.

Novel compound heterozygous mutation in WEE2 is associated with fertilization failure: case report of an infertile woman and literature review

BACKGROUND

Fertilization failure after intracytoplasmic sperm injection continues to affect couples and the etiology is not well-understood.

CASE PRESENTATION

We characterized a couple with 2-year history of primary unexplained infertility. Three different assisted reproduction attempts (IVF + rescue ICSI, ICSI and ICSI-AOA) showed repeated fertilization failure for MII oocyte retrieval after controlled ovarian hyperstimulation. After whole-exome sequencing and sanger sequencing of the couple and their family members, variant pathogenicity was assessed using SIFT, PolyPhen2, Mutation Taster, and Human Splicing Finder software. We identified novel compound heterozygous mutations, c.1535 + 3A > G and c.946C > T (p. Leu316Phe), in WEE2 in the female proband. Trios analysis of the variations revealed an autosomal recessive pattern. c.1535 + 3A > G in WEE2 was predicted to break the wild-type donor site and affect splicing, and the missense mutation c.946C > T (p. Leu316Phe) of WEE2 was predicted to be pathogenic.

CONCLUSION

A novel compound heterozygous mutation in WEE2 was identified in an infertile female who experienced repeated fertilization failure even after ICSI-AOA. These novel mutations in WEE2 provided genetic evidence for fertilization failure.

Novel compound heterozygous mutations in WEE2 causes female infertility and fertilization failure

PURPOSE

To identify the disease-causing gene in a family with female infertility and fertilization failure.

METHODS

Whole-exome sequencing and Sanger sequencing were used to identify the disease-causing gene in a female with infertility and fertilization failure. Subcellular localization and western blot analysis were used to check the effect of mutations.

RESULTS

We identified novel compound heterozygous mutations c.598C>T (p.Arg200Ter) and c.1319G>C (p.Trp440Ser) in WEE2 gene in a female with infertility and fertilization failure. The p.Arg200Ter mutant WEE2 gene produce truncated protein and mainly located in the nucleus, the same as the wild protein, while the p.Trp440Ser mutant WEE2 proteins are located in the nucleus and cytoplasm and the expression level of p.Trp440Ser mutant WEE2 protein is reduced significantly compared with that of wild-type WEE2.

CONCLUSIONS

We discovered novel compound heterozygous mutations c.598C>T (p.Arg200Ter) and c.1319G>C (p.Trp440Ser) in WEE2 gene in a female whose oocytes could not form pronucleus after intracytoplasmic sperm injection (ICSI). Moreover, mutations in WEE2 gene affect the normal function of WEE2 proteins and cause fertilization failure.

New biallelic mutations in WEE2: expanding the spectrum of mutations that cause fertilization failure or poor fertilization

OBJECTIVE

To investigate the genetic cause of fertilization failure or poor fertilization.

DESIGN

Genetic analysis.

SETTING

University-affiliated center.

PATIENT(S)

Twenty-four Chinese women who underwent assisted reproductive technology (ART) and had repeated fertilization failure or poor fertilization.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Twenty-four affected patients were subjected to whole-exome sequencing and candidate mutations were validated by Sanger sequencing. Single-cell reverse transcription was used to analyze the functional characterization of the splice-site mutation in vivo. Evolutionary conservation and molecular modeling analyses were used to predict the impact of missense mutations on secondary protein structure. Immunofluorescence was used to analyze the protein levels of WEE2 and phosphorylated CDC2.

RESULT(S)

Biallelic mutations in WEE2 were identified in 5 of 24 (20.8%) Chinese patients with fertilization failure or poor fertilization. Among these individuals we found a novel splice-site mutation, two novel missense mutations, and a previously reported frame-shift mutation. Splicing mutation c.1136-2A>G of WEE2 caused an alteration of the reading frame and introduced a premature stop codon (p.Gly379Glufs*6/p.Asp380Leufs*39). The missense mutations c.585G>C (p.Lys195Asn) and c.1228C>T (p.Arg410Trp) produced obvious changes in secondary protein structures. Immunostaining indicated that mutated WEE2 resulted in the loss of phosphorylated CDC2. The phenotypes of women carrying WEE2 mutations exhibited slight variability, from total fertilization failure to poor fertilization.

CONCLUSION(S)

Novel mutations in the known causative gene WEE2 were identified in 5 of 24 women with fertilization failure or poor fertilization, indicating a high prevalence of WEE2 mutations in Chinese women experiencing fertilization failure or poor fertilization.

Homozygous missense mutation Arg207Cys in the WEE2 gene causes female infertility and fertilization failure

PURPOSE

To investigate a novel mutation in the WEE2 gene in a female patient with primary infertility and fertilization failure.

METHODS

Sanger sequencing was used to detect mutations in WEE2. The pathogenicity of the identified variant and its possible effects on the WEE2 protein were evaluated with in silico tools and molecular modeling. We used the calcium ionophore A23187 as a chemical activator of oocytes after intracytoplasmic sperm injection (ICSI).

RESULTS

We identified a consanguineous family with a novel homozygous missense mutation in WEE2 (c.619C>T [p.R207C]). Based on preliminary bioinformatics analysis, we speculate that the novel homozygous missense mutation is pathogenic. ICSI combined with assisted oocyte activation (ICSI-AOA) did not overcome fertilization failure in this patient with WEE2 mutation.

CONCLUSIONS

We identified a novel mutation in WEE2 (c.619C>T [p.R207C]) in a female patient with fertilization failure after ICSI, and we provide evidence that this novel homozygous missense mutation can cause fertilization failure.