Copy Number Variations in Female Infertility in China

Copy number variations (CNVs) and karyotyping analysis in males with azoospermia and oligospermia

BACKGROUND

Considering the essential roles that genetic factors play in azoospermia and oligospermia, this study aims to identify abnormal chromosomes using karyotyping and CNVs and elucidate the associated genes in patients.

METHODS

A total of 1157 azoospermia and oligospermia patients were recruited, of whom, 769 and 674 underwent next-generation sequencing (NGS) to identify CNVs and routine G-band karyotyping, respectively.

RESULTS

First, 286 patients were co-analyzed using CNV sequencing (CNV-seq) and karyotyping. Of the 725 and 432 patients with azoospermia and oligospermia, 33.8% and 48.9% had abnormal karyotypes and CNVs, respectively. In particular, 47,XXY accounted for 44.18% and 26.33% of abnormal karyotypes and CNVs, respectively, representing the most frequent genetic aberration in azoospermia and oligospermia patients. Nevertheless, big Y and small Y accounted for 7.46% and 16.67% of abnormal karyotypes, respectively. We also identified high-frequency CNVs-loci, such as Xp22.31 and 2p24.3, in azoospermia and oligospermia patients.

CONCLUSION

Sex chromosome and autosomal CNV loci, such as Xp22.31 and 2p24.3, as well as the associated genes, such as VCX and NACAP9, could be candidate spermatogenesis genes. The high-frequency abnormal karyotypes, CNV loci, and hot genes represent new targets for future research.

Meiosis interrupted: the genetics of female infertility via meiotic failure

Idiopathic or 'unexplained' infertility represents as many as 30% of infertility cases worldwide. Conception, implantation, and term delivery of developmentally healthy infants require chromosomally normal (euploid) eggs and sperm. The crux of euploid egg production is error-free meiosis. Pathologic genetic variants dysregulate meiotic processes that occur during prophase I, meiotic resumption, chromosome segregation, and in cell cycle regulation. This dysregulation can result in chromosomally abnormal (aneuploid) eggs. In turn, egg aneuploidy leads to a broad range of clinical infertility phenotypes, including primary ovarian insufficiency and early menopause, egg fertilization failure and embryonic developmental arrest, or recurrent pregnancy loss. Therefore, maternal genetic variants are emerging as infertility biomarkers, which could allow informed reproductive decision-making. Here, we select and deeply examine human genetic variants that likely cause dysregulation of critical meiotic processes in 14 female infertility-associated genes: SYCP3, SYCE1, TRIP13, PSMC3IP, DMC1, MCM8, MCM9, STAG3, PATL2, TUBB8, CEP120, AURKB, AURKC, andWEE2. We discuss the function of each gene in meiosis, explore genotype-phenotype relationships, and delineate the frequencies of infertility-associated variants.