The prevalence of common CFTR mutations in Iranian infertile men with non-CAVD obstructive azoospermia by using ARMS PCR techniques

The relationship between common mutations in CFTR, AR genes, Y chromosome microdeletions and karyotyping abnormalities with very severe oligozoospermia in Iranian men

BACKGROUND

Male infertility due to very severe oligozoospermia has been associated with some genetic risk factors.

OBJECTIVE

To investigate the distribution of the mutations in the CFTR gene, the CAG-repeat expansion of the AR gene, also Y chromosome microdeletions and karyotyping abnormalities in very severe oligozoospermia patients.

METHODS

In the present case-control study, 200 patients and 200 fertile males were enrolled. All patients and control group were karyotyped. Microdeletions were evaluated using multiplex PCR. Five common CFTR mutations were genotyped using the ARMS-PCR technique. The CAG-repeat expansion in the AR gene was evaluated for each individual using sequencing.

RESULTS

Overall 4% of cases shows a numerical and structural abnormality. 7.5% of patients had a deletion in one of the AZF regions on Yq, and 3.5% had a deletion in two regions. F508del was the most common (4.5%) CFTR gene mutation; G542X, and W1282X were detected with 1.5% and 1% respectively. One patient was found to have AZFa microdeletion and F508del in heterozygote form; one patient had AZFb microdeletion with F508del. F508del was seen as compound heterozygous with G542X in one patient and with W1282X in the other patient. The difference in the mean of the CAG-repeats in the AR gene in patients and control groups was statistically significant (P = 0.04).

CONCLUSION

Our study shows the genetic mutations in men with severe oligozoospermia and given the possibility of transmission of these disorders to the next generation by fertilization, counseling and genetic testing are suggested for these couples before considering ICSI.

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

In brief

The genetic heterogeneity of CFTR gene mutations in Chinese patients with congenital absence of the vas deferens (CAVD) differs from the hotspot mutation pattern in Caucasians. This paper reviews and suggests a more suitable screening strategy for the Chinese considering the dilemma of CFTR genetic blocking.

Abstract

Congenital absence of the vas deferens (CAVD) is a major cause of obstructive azoospermia and male infertility, with CFTR gene mutation as the main pathogenesis. Other genes such as ADGRG2, SLC9A3, and PANK2 have been discovered and proven to be associated with CAVD in recent studies. Multiple CFTR hotspot mutations have been found in Caucasians in several foreign countries, and relevant genetic counseling and preimplantation genetic diagnosis (PGD) have been conducted for decades. However, when we examined research on Chinese CAVD, we discovered that CFTR mutations show heterogeneity in the Chinese Han population, and there is currently no well-established screening strategy. Therefore, we have reviewed the literature, combining domestic and international research as well as our own, aiming to review research progress on the CFTR gene in China and discuss the appropriate scope for CFTR gene detection, the detection efficiency of other CAVD-related genes, and the screening strategy applicable to the Chinese Han population. This study provides more valuable information for genetic counseling and a theoretical basis for PGD and treatment for couples with CAVD when seeking reproductive assistance.

Prevalence of CBAVD in azoospermic men carrying pathogenic CFTR mutations - Evaluated in a cohort of 639 non-vasectomized azoospermic men

BACKGROUND

Men with obstructive azoospermia (OA) due to impaired development of the genital tract often carry at least one Cystic Fibrosis Transmembrane Conductance Regulator CFTR mutation.

OBJECTIVE

To determine the frequency of Congenital Bilateral Absence of Vas deferens (CBAVD) in men with azoospermia carrying CFTR gene mutations.

MATERIALS AND METHODS

Non-vasectomized men with azoospermia referred to our andrological center were consecutively included. All men underwent palpation of the scrotal parts of the Vasa deferentia, ultrasonography of the testicles and hormone profile, and genetic analyses. Testicular biopsy was usually performed. A panel of 32 of the most important CFTR mutations was examined from genomic DNA isolated from blood lymphocytes. Either multiplex PCR analysis or a next-generation sequencing technique was performed.

RESULTS

Among the 639 men with azoospermia, 69 (10.8%) had at least one CFTR mutation. Of the 43 patients with at least one of the two CFTR mutations, ΔF508 and R117H, 19 (44.2%) showed CBAVD, 2 (4.7%) Congenital Unilateral Absence of Vas deferens (CUAVD), and 22 (51.2%) presence of the scrotal parts of the Vasa deferentia. In contrast, only 1/21 men (4.8%) with an isolated IVS8-5T variant showed CBAVD. Among the further 20 men with an isolated IVS8-5T variant, 11 had a history of cryptorchidism. Among the 570 men without CFTR mutations, CBAVD was found in only two men and CUAVD in one. FSH level was higher and testicular volume lower in men with present Vasa deferentia compared to those without (P < .001; Student's t test). Thirty-one men with either ΔF508 or R117H mutations, or both, had a testicular biopsy. Motile spermatozoa were found in 100% of 16 cases with CBAVD but in only 6 out of 15 cases with present Vasa deferentia (P < .01; Fisher's exact test).

DISCUSSION AND CONCLUSIONS

CBAVD was found in ~ 44% of men with ΔF508/R117H mutations. The data may support that CFTR mutations might affect male fertility through other mechanisms than obstruction of the genital tract. For a practical, clinical purpose analysis for only ΔF508, R117H and IVS8-5T seems sufficient until further research shows anything else.

A Survey of the Common Mutations and IVS8-Tn Polymorphism of Cystic Fibrosis Transmembrane Conductance Regulator Gene in Infertile Men with Nonobstructive Azoospermia and CBAVD in Iranian Population

Background

Studies have revealed a strong association between mutations of CFTR gene and the congenital bilateral absence of the vas deferens (CBAVD), but the role of this gene in other types of male infertility is still unclear. The purpose of this study was to investigate the frequency of the most common mutations of the CFTR gene (DF508, G542X, N1303K, G551D, and W1282X) in a population of infertile men with nonobstructive azoospermia (NOA) and CBAVD in Iran.

Methods

Blood samples were obtained from 50 NOA, 50 CBAVD, and 100 normal males (control). Genomic DNA was isolated from whole blood leukocytes, and the presence of common mutations of the CFTR gene was assessed by an amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Restriction fragment length polymorphism (PCR-RFLP) was also used to analyze IVS8-Tn polymorphism.

Results

It was found that 16%, 8%, and 8% of patients with CBAVD were heterozygote for DF508, G542X, and N1303K, respectively. The frequency of the 5T allele was 34% and higher than the normal group (p < 0.001). None of the common CFTR gene mutations were detected in NOA patients, and no significant difference was found in the distribution of the 5T allele between the NOA patients and the control group (5 vs. 3 p = 0.721).

Conclusion

Based on the present case-control study, the CFTR gene mutations and IVS8-Tn polymorphisms are correlated with CBAVD; however, extensive investigations are necessary to determine the exact relationship between the gene mutations and other forms of male infertility.

A Survey of the Common Mutations and IVS8-Tn Polymorphism of Cystic Fibrosis Transmembrane Conductance Regulator Gene in Infertile Men with Nonobstructive Azoospermia and CBAVD in Iranian Population

Background

Studies have revealed a strong association between mutations of CFTR gene and the congenital bilateral absence of the vas deferens (CBAVD), but the role of this gene in other types of male infertility is still unclear. The purpose of this study was to investigate the frequency of the most common mutations of the CFTR gene (DF508, G542X, N1303K, G551D, and W1282X) in a population of infertile men with nonobstructive azoospermia (NOA) and CBAVD in Iran.

Methods

Blood samples were obtained from 50 NOA, 50 CBAVD, and 100 normal males (control). Genomic DNA was isolated from whole blood leukocytes, and the presence of common mutations of the CFTR gene was assessed by an amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Restriction fragment length polymorphism (PCR-RFLP) was also used to analyze IVS8-Tn polymorphism.

Results

It was found that 16%, 8%, and 8% of patients with CBAVD were heterozygote for DF508, G542X, and N1303K, respectively. The frequency of the 5T allele was 34% and higher than the normal group (p < 0.001). None of the common CFTR gene mutations were detected in NOA patients, and no significant difference was found in the distribution of the 5T allele between the NOA patients and the control group (5 vs. 3 p = 0.721).

Conclusion

Based on the present case-control study, the CFTR gene mutations and IVS8-Tn polymorphisms are correlated with CBAVD; however, extensive investigations are necessary to determine the exact relationship between the gene mutations and other forms of male infertility.

CFTR variants and renal abnormalities in males with congenital unilateral absence of the vas deferens (CUAVD): a systematic review and meta-analysis of observational studies

PURPOSE

CFTR variant is the main genetic contributor to congenital (unilateral/bilateral) absence of the vas deferens (CAVD/CUAVD/CBAVD). We performed a systematic review to elucidate the genetic link between CFTR variants, CUAVD, and the associated risk of renal abnormality (RA).

METHODS

We searched relevant databases for eligible articles reporting CFTR variants in CUAVD. The frequency of CFTR variants and RA, and the odds ratios (ORs) for common alleles and RA risk, were pooled under random-/fixed-effect models. Subgroup analyses and heterogeneity tests were performed.

RESULTS

Twenty-three studies were included. Among CUAVD patients, 46% had at least one CFTR variant, with 27% having one and 5% having two. The allele frequency in CUAVD was 4% for F508del and 9% for 5T. The summary OR for 5T risk in CUAVD was 5.79 compared with normal controls and 2.82 compared with non-CAVD infertile males. The overall incidence of RA was 22% in CUAVD. The pooled OR for RA risk among CUAVD patients was 4.85 compared with CBAVD patients.

CONCLUSION

CFTR variants are common in CUAVD, and the 5T allele may be associated with increased CUAVD risk. CUAVD patients bear a higher RA risk than CBAVD patients, but this is not associated with CFTR variants.

Screening of Two Neighboring CFTR Mutations in Iranian Infertile Men with Non-Obstructive Azoospermia

The genetic association between cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations and male infertility due to congenital bilateral absence of vas deferens (CBAVD) is well established. Mutant CFTR, however may also be involved in the etiology of male infertility in non-CBAVD cases. The present study was conducted to estimate the frequency of ∆I507 and ∆F508 CFTR gene mutations in Iranian infertile males. We undertook the first study of association between these CFTR mutations and non-obstructive azoospermia in Iran. In this case-control study, 100 fertile healthy fathers and 100 non-obstructive azoospermia’s men were recruited from Isfahan Infertility Center (IIC) and Sari Saint Mary’s Infertility Center, between 2008 and 2009. Screening of F508del and I507del mutations was carried out by the multiplex-ARMS-PCR. Significance of differences in mutation frequencies between the patient and control groups was assessed by Fisher’s exact test. The ΔF508 was detected in three patients. However there are no significant association was found between the presence of this mutated allele and infertility [OR=9.2 (allele-based) and 7.2 (individual-based), P=0.179]. None of the samples carried the ΔI507 mutation. Altogether, we show that neither ΔI507 nor ΔF508 is involved in this population of Iranian infertile males with non-obstructive azoospermia.

Increased frequency of CFTR gene mutations identified in Indian infertile men with non-CBAVD obstructive azoospermia and spermatogenic failure

High incidence of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene is associated with congenital bilateral absence of the vas deferens (CBAVD) and is considered as the genital form of cystic fibrosis (CF). The CFTR gene may also be involved in the etiology of male infertility in cases other than CBAVD. The present study was conducted to identify the spectrum and frequency of CFTR gene mutations in infertile Indian males with non-CBAVD obstructive azoospermia (n=60) and spermatogenic failure (n=150). Conspicuously higher frequency of heterozygote F508del mutation was detected in infertile males with non-CBAVD obstructive azoospermia (11.6%) and spermatogenic failure (7.3%). Homozygous IVS(8)-5T allele frequency was also significantly higher in both groups in comparison to those in normal healthy individuals. Two mutations in exon 25 viz., R1358I and K1351R were identified as novel mutations in patients with non-CBAVD obstructive azoospermia. Mutation R1358I was predicted as probably damaging CFTR mutation. This is the first report from the Indian population, emphasizing increased frequency of CFTR gene mutations in male infertility other than CBAVD. Thus, it is suggested that screening of CFTR gene mutations may be required in infertile Indian males with other forms of infertility apart from CBAVD and willing for assisted reproduction technology.

Regulation of male fertility by CFTR and implications in male infertility

BACKGROUND

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated Cl(-) and HCO(3)(-) conducting channel, mutations of which are known to be associated with male infertility. However, the underlying mechanisms remain elusive.

METHODS

Literature databases were searched for papers on the topics related to CFTR and male fertility and infertility with relevant keywords. Unpublished data from authors' laboratory were also included for analysis.

RESULTS

Clinical evidence shows increased mutation frequency or reduced CFTR expression in men with congenital bilateral absence of vas deferens (CBAVD) or sperm abnormalities, such as azoospermia teratospermia and oligoasthenospermia. Studies on primary rodent Sertoli cells and germ cells, as well as testes from CFTR knockout mice or a cryptorchidism model, yield findings indicating the involvement of CFTR in spermatogensis through the HCO(3)(-)/sAC/cAMP/CREB(CREM) pathway and the NF-κB/COX-2/PGE(2) pathway. Evidence also reveals a critical role of CFTR in sperm capacitation by directly or indirectly mediating HCO(3)(-) entry that is essential for capacitation. CFTR is emerging as a versatile player with roles in mediating different signaling pathways pertinent to various reproductive processes, in addition to its long-recognized role in electrolyte and fluid transport that regulates the luminal microenvironment of the male reproductive tract.

CONCLUSIONS

CFTR is a key regulator of male fertility, a defect of which may result in different forms of male infertility other than CBAVD. It would be worthwhile to further investigate the potential of developing novel diagnostic and contraceptive methods targeting CFTR.