Limited ability of increased sequencing depth in detecting cases missed by noninvasive prenatal testing: a comparative analysis of 3 clinical cases.

Increased sequencing depth can improve the detection rate of noninvasive prenatal testing (NIPT) for chromosome aneuploidies and copy number variations (CNVs). However, due to the technical limitations of NIPT, false-positives and false-negatives are inevitable. False-positives for aneuploidy and CNVs have been widely reported, but few missed cases have been reported. In this study, we report 3 patients missed by NIPT, which were still missed after increasing the sequencing depth. To verify the detection efficiency of the platform, the results of NIPT in 32,796 patients treated in Yulin Women and Children Health Care Hospital from 2020 to 2022 were retrospectively analyzed. Data on false-negative cases found by postnatal follow-up or amniocentesis were collected, and the sequencing data, pregnancy examination data, and postnatal follow-up results of these missed patients were summarized. Five patients missed by NIPT were found, and they were missed again by retesting or increasing the sequencing depth. Except for hypospadias found in 1 patient, ultrasonography of the other 4 patients showed no obvious abnormalities during the whole pregnancy. Our results suggest that pregnant women should be fully informed of the benefits and limitations of NIPT before undergoing the examination to avoid unnecessary medical disputes.

A novel ADGRG2 truncating variant associated with X-linked obstructive azoospermia in a large Chinese pedigree.

PURPOSE: In this study, we aimed to identify sterility-related variants in a Chinese pedigree with male infertility and to reveal the different phenotypes and intracytoplasmic sperm injection (ICSI) outcomes of the affected members. METHODS: Physical examinations were performed on male patients. G-band karyotype analysis, copy number variation sequencing, and quantitative fluorescent PCR were conducted to detect common chromosomal disorders in the probands. Whole-exome sequencing and Sanger sequencing were applied to identify the pathogenic genes and the protein expression changes caused by the very mutation were identified by Western Blot in vitro. RESULTS: A novel nonsense mutation (c.908C > G: p.S303*) in the ADGRG2 was identified in all infertile male patients of the pedigree, which was inherited from their mothers. This variant was absent from the human genome databases. This mutation was also unexpectedly found in a male member with normal reproductive capability. Members with the mutation had different genitalia phenotypes, ranging from normal to dilated phenotypes of the vas deferens, spermatic veins and epididymis. There was a truncated ADGRG2 protein in vitro after mutation. Of the three patients' wives treated with ICSI, only one successfully gave birth. CONCLUSIONS: Our study is the first to report the c.908C > G: p.S303* mutation in the ADGRG2 in an X-linked azoospermia pedigree and is the first to report normal fertility in a member with this mutation, expanding the mutation spectrum and phenotype spectrum of this gene. In our study, ISCI had a success rate of only one-third in couples including men with azoospermia with this mutation.