A case report of a rare nonsense ZP1 variant in a patient with oocyte maturation defect

After four unsuccessful assisted reproductive techniques trials, a female was referred for genetic analysis. In this case study, we aimed to investigate the genetic etiology of a female with infertility and oocyte maturation defect. Chromosome analysis and fluorescence in-situ hybridization (FISH) using X-centromer-ic (DXZ1) and SHOX-probe (SHOX/SE X) (CytoCell, Cambridge, UK) on interphase nuclei of lymphocytes and mucosal cells were performed. Exome sequencing using the Illumina platform and confirmatory studies, including intra-familial segregation analy-sis, was done by Sanger sequencing. Karyotyping and molecular cytogenetics studies were normal, and potential chromosomal abnormalities and mosaicism were excluded. WES data analy-sis identified a known, rare, nonsense pathogenic homozygous variant in exon 3 (NM_207341.4, c.628C>T; p.Q210*) of the ZP1 gene. Additionally, her parents, who were first-degree cousins, were heterozygotes for this variant. Zona pellucida is an essen-tial glycoprotein that surrounds oocytes and contains four types of receptor proteins (ZP1-4). The detected mutation in the ZP1 gene leads to the premature stop codon, causing truncation of the ZP1 receptor protein. This is the first case report with a homozygous variant associated with oocyte maturation defect. Also, exome sequencing is a valuable method to identify the genetic etiology in complex, multigenic conditions like infertility.