Compound heterozygous variants in CFTR with potentially reducing ATP-binding ability identified in Chinese infertile brothers with isolated congenital bilateral absence of vas deferens

BACKGROUND

Isolated congenital bilateral absence of vas deferens (iCBAVD) in men results in obstructive azoospermia and is mainly caused by pathogenic variants in cystic fibrosis transmembrane conductance regulator (CFTR) or adhesion G protein-coupled receptor G2 (ADGRG2).

METHODS

The next-generation sequencing (NGS) was used to screen the mutations in the proband, and Sanger sequencings were performed to validate the compound heterozygous variant of CFTR in his family members. Protein structure simulation was performed to discover the potential pathological mechanism.

RESULTS

This study reported novel compound heterozygous CFTR mutations (NM:000492.4, Intron: 5T; c.3965_3969dupTTGGG: p.R1325Gfs*5) in two brothers with obstructive azoospermia. The compound heterozygous CFTR mutations were first screened out by NGS in an infertile male patient who exhibited iCBAVD from a nonconsanguineous Chinese family. Histological analysis of the testicular biopsy from this patient revealed normal spermatogenesis and mature spermatozoa were observed in the seminiferous tubules. Surprisingly, the same compound heterozygous CFTR mutations were also observed in his brothers who also exhibited iCBAVD, with their parents being a heterozygous carrier for the mutations, as verified by Sanger sequencing. Protein structure simulation revealed that these mutations potentially led to impaired ATP-binding ability of CFTR.

CONCLUSION

We identified novel compound heterozygous CFTR mutations in two brothers and summarized the literature regarding CFTR mutation and male infertility. Our study may contribute to the genetic diagnosis of iCBAVD and future genetic counseling.

Cystic fibrosis transmembrane conductance regulator-related male infertility: Relevance of genetic testing & counselling in Indian population

Background & objectives:

Due to limited information available on the frequency and spectrum of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene mutations in congenital bilateral absence of vas deferens (CBAVD) in Indian population, it is difficult to provide accurate genetic counselling to couples. The present study was undertaken to investigate the spectrum and frequency of CFTR gene mutations in Indian men with CBAVD and to determine the female CF carrier status.

Methods:

Direct DNA sequencing of the CFTR gene was carried out in eighty CBAVD men, their female partners and fifty controls from the general population. Pathological significance of the identified novel CFTR gene variants was carried out using in silico tools. Appropriate genetic counselling was provided to the couples prior to intracytoplasmic sperm injection (ICSI).

Results:

A significant association was observed for CFTR gene variants in Indian CBAVD men versus controls (odds ratio: 12.1; 95% confidence interval: 4.8-30.4; P<0.0001). A total of 20 CFTR gene variants were identified in 53 CBAVD men. Eight novel missense CFTR gene variants (L214V, A238P, E379V, L578I, F587L, L926W, R1325K and R1453Q); two novel splice-site gene variants (c.1-30C>G and IVS1+2T>G) and ten previously reported mutations (R75Q, c.1210-12[5], F508del, A309G, R334W, I444T, R668C, R709X, A1285V and Q1352H) were detected in CBAVD men. The novel and reported CFTR gene mutations were L926W (2.5%, P=0.26), R1453Q (2.5%, P=0.26), F508del (8.75%, P=0.03) and c.1210-12[5] (42.5%, P=0.002). A total of 13 (16.2%) female partners were found to be a CF carrier. Nine couples had a risk of transmitting mutant CFTR allele to the offspring.

Interpretation & conclusions:

The heterogeneous spectrum of CFTR gene in Indian population suggests the necessity of screening CBAVD men and female partners for accurate genetic counselling prior to undergoing ICSI.

External and Genetic Conditions Determining Male Infertility

We explain environmental and genetic factors determining male genetic conditions and infertility and evaluate the significance of environmental stressors in shaping defensive responses, which is used in the diagnosis and treatment of male infertility. This is done through the impact of external and internal stressors and their instability on sperm parameters and their contribution to immunogenetic disorders and hazardous DNA mutations. As chemical compounds and physical factors play an important role in the induction of immunogenetic disorders and affect the activity of enzymatic and non-enzymatic responses, causing oxidative stress, and leading to apoptosis, they downgrade semen quality. These factors are closely connected with male reproductive potential since genetic polymorphisms and mutations in chromosomes 7, X, and Y critically impact on spermatogenesis. Microdeletions in the Azoospermic Factor AZF region directly cause defective sperm production. Among mutations in chromosome 7, impairments in the cystic fibrosis transmembrane conductance regulator CFTR gene are destructive for fertility in cystic fibrosis, when spermatic ducts undergo complete obstruction. This problem was not previously analyzed in such a form. Alongside karyotype abnormalities AZF microdeletions are the reason of spermatogenic failure. Amongst AZF genes, the deleted in azoospermia DAZ gene family is reported as most frequently deleted AZF. Screening of AZF microdeletions is useful in explaining idiopathic cases of male infertility as well as in genetic consulting prior to assisted reproduction. Based on the current state of research we answer the following questions: (1) How do environmental stressors lessen the quality of sperm and reduce male fertility; (2) which chemical elements induce oxidative stress and immunogenetic changes in the male reproductive system; (3) how do polymorphisms correlate with changes in reproductive potential and pro-antioxidative mechanisms as markers of pathophysiological disturbances of the male reproductive condition; (4) how do environmental stressors of immunogenetic disorders accompany male infertility and responses; and (5) what is the distribution and prevalence of environmental and genetic risk factors.

The CFTR gene mild variants poly-T, TG repeats and M470V detection in Indian men with congenital bilateral absence of vas deferens

The aim of the study was to detect the frequency of the CFTR gene variants poly-T, TG repeats and c.1408A>G p.Met470Val (M470V) in Indian men with congenital bilateral absence of the vas deferens (CBAVD). Men diagnosed with CBAVD (n = 76), their female partners (n = 76) and healthy men from general population (n = 50) were recruited. Genomic DNA was isolated and the polymorphic regions of IVS9- c.1210-12T [5] and M470V were amplified using specific primers followed by Sanger's DNA sequencing. A statistically significant increase in the frequency of heterozygous IVS9- c.1210-12T [5] (39.4%) was observed in CBAVD men as compared to controls (14%). The allelic distribution of c.1210-12T [5], c.1210-12T [7] and c.1210-12T [9] in CBAVD men was 21%, 64.4% and 13% and that in healthy controls was 7%, 73% and 20% respectively. Longest TG repeat c.1210-34TG [13] was found in association with c.1210-12T [5] with an allelic frequency of 5.9% in CBAVD men. We found a significant association of c.1210-34TG [12]/c.1210-34TG [13] - c.1210-12[5] -V470 allele in CBAVD men. Twelve female partners harboured a heterozygous c.1210-12T [5] allele. The study emphasises the need to screen both partners for the polymorphisms M470V, poly-T, TG tract repeats in addition to population-specific known CFTR gene mutations.

Association of cystic fibrosis transmembrane-conductance regulator gene mutation with negative outcome of intracytoplasmic sperm injection pregnancy in cases of congenital bilateral absence of vas deferens

OBJECTIVE

To evaluate intracytoplasmic sperm injection (ICSI) results with regard to congenital bilateral absence of vas deferens (CBAVD) versus non-CBAVD obstruction, cystic fibrosis transmembrane-conductance regulator (CFTR) mutations versus non-CFTR mutations, and miscarriages or stillbirths versus live births per embryo transferred.

DESIGN

Retrospective study with detailed chart review.

SETTING

Center for reproductive medicine.

PATIENT(S)

Nine hundred forty-five men with obstructive azoospermia.

INTERVENTION(S)

One thousand four hundred fourteen ICSI cycles classified as CBAVD versus non-CBAVD obstruction, CFTR mutations versus non-CFTR mutations, and miscarriages/stillbirths versus live births per embryo transferred.

MAIN OUTCOME MEASURE(S)

Frequency of CFTR mutations and rates of fertilization, good embryos, clinical pregnancy, miscarriages and stillbirths, ectopic pregnancy, and live births.

RESULT(S)

CFTR mutations were more prevalent in men with CBAVD than in those with non-CBAVD obstruction. The rate of miscarriages and stillbirths per embryo transferred was higher in men with CBAVD than in those with non-CBAVD obstruction, whereas the rate of live births per embryo transferred was lower in men with CBAVD than in those with non-CBAVD obstruction. The rate of miscarriages and stillbirths per embryo transferred was higher in men with CFTR mutations than in those with non-CFTR mutations. The frequency of CFTR mutations was higher in patients who experienced miscarriages/stillbirths than in those with live births.

CONCLUSION(S)

The frequency of CFTR mutations was higher in cases of CBAVD versus non-CBAVD obstruction. Possibly as a result of CFTR mutations, patients with CBAVD had a significantly increased risk of miscarriage and stillbirth and a reduced rate of live birth compared with patients with non-CBAVD.