Heterogeneous spectrum of CFTR gene mutations in Chinese patients with CAVD and the dilemma of genetic blocking strategy

An overview of CFTR mutation profiles and assisted reproductive technology outcomes in Chinese patients with congenital obstructive azoospermia

PURPOSE

The cystic fibrosis transmembrane conductance regulator (CFTR) is the most common causative gene attributed to congenital obstructive azoospermia (OA). The aim of this study was to conduct an epidemiological survey of congenital OA patients, to screen for CFTR mutations, and to follow their pregnancy outcomes in assisted reproductive technology (ART).

METHODS

This cohort study enrolled congenital OA patients undergoing ART and whole-exome sequencing from January 2018 to September 2023. Semen parameters, sex hormones, and seminal plasma biochemistry were evaluated. CFTR mutations identified in OA patients were analyzed. In addition, the laboratory outcomes, clinical outcomes, and neonatal outcomes were compared between OA patients carrying two CFTR mutations and the others after surgical sperm extraction-intracytoplasmic sperm injection (ICSI) treatment.

RESULTS

A total of 76 patients with congenital OA were enrolled. CFTR mutations were identified in 35 (46.1%) congenital OA patients. A total of 60 CFTR mutation sites of 27 types were identified, and 10 of them were novel. The average frequency was 1.71 (60/35) per person. The most common mutation was c.1210-11T > G (25%, 15/60). After ICSI treatment, there were no statistically significant differences in laboratory outcomes, clinical outcomes, and neonatal outcomes between OA patients carrying two CFTR mutations (n = 25) and other OA patients (n = 51).

CONCLUSION

Apart from the IVS9-5T mutation, the genetic mutation pattern of CFTR in Chinese OA patients is heterogeneous, which is significantly different from that of Caucasians. Although carrying two CFTR mutations or not had no effect on the pregnancy outcomes in OA patients after ICSI, genetic counseling is still recommended for such patients.

Whole exome sequencing reveal 83 novel Mendelian disorders carrier P/LP variants in Chinese adult patients

Carrier screening can identify people at risk of conceiving pregnancies affected with inherited genetic disorders or who have a genetic disorder with late or variable onset. Carrier screening based on whole exome sequencing (WES) data can offer more comprehensive assessment than on-target carrier screening tests. A total of 224 Chinese adult patients WES data was analyzed, except positive variants associated with the patients' major complaint, 378 pathogenic (P) and "likely pathogenic" (LP) variants from 175 adult patients were identified. Whole exome-wide frequency of carriers for Mendelian disorders in Chinese adult patients was about 78.13% in this study, which was lower than the previously reported carrier frequency in healthy population. Contrary to expectations, the number of P or LP variants did not increase with larger chromosome size or decrease with smaller chromosome size. Totally 83 novel P or LP variants were identified which could further expand the carrier variants spectrum of the Chinese population. GJB2: NM_004004.6:c.299_300delAT:p.His100fs*14 and C6:NM_000065.4:c.654T>A:p.Cys218* were found in two or more patients, which might be two underestimated carrier variants in Chinese population. We also found 9 late-onset or atypical symptoms autosomal/X-linked dominant Mendelian disorders causative genes, which were easily overlooked during pathogenicity analysis. These results can provide a strong basis for preventing and avoiding the prevalence rates of birth defects and reducing social and family burdens. By comparing with three different expanded carrier screening gene panels, we further confirmed carrier screening based on WES could offer more comprehensive assessment and WES was applicable for carrier screening.