Involvement of CFTR gene alterations in obstructive and nonobstructive infertility in men

The prevalence of common CFTR gene mutations and polymorphisms in infertile Iranian men with very severe oligozoospermia

Due to progress in infertility etiology, several genetic bases of infertility are revealed today. This study aimed to investigate the distribution of mutations in the CFTR gene, M470V polymorphism, and IVS8 poly T. Furthermore, we aimed to examine the hotspot exons (4, 7, 9, 10, 11, 20, and 21 exons) to find a new mutation in cystic fibrosis transmembrane conductance regulator (CFTR) gene among infertile Iranian men very severe oligozoospermia (<1 million sperm/mL ejaculate fluid). In the present case-control study, 200 very severe oligozoospermia (20-60s) and 200 fertile men (18-65s) were registered. Five common CFTR mutations were genotyped using the ARMS-PCR technique. The M470V polymorphism was checked out by real-time PCR, and poly T and exons were sequenced. The F508del was the most common (4.5%) CFTR gene mutation; G542X and W1282X were detected with 1.5% and 1%, respectively. N1303K and R117H were detected in 0.5% of cases. F508del was seen as a heterozygous compound with G542X in one patient and with W1282X in the other patient. Also, in the case of M470V polymorphism, there are differences between the case and control groups (p=0.013). Poly T assay showed statistical differences in some genotypes. The study showed no new mutation in the exons mentioned above. Our results shed light on the genetic basis of men with very severe oligozoospermia in the Iranian population, which will support therapy decisions among infertile men.

Identification and selection of healthy spermatozoa in heterozygous carriers of the Phe508del-variant of the CFTR-gene in assisted reproduction

The pathogenic variant Phe508del of the CFTR-gene is the most frequent cause of cystic fibrosis (CF). Whereas male CF-patients are infertile due to bilateral agenesis of the efferent ducts, the fertility status of male heterozygous carriers is uncertain. We aimed at demonstrating the involvement of the CFTR-ion channel during sperm capacitation and to potentially select variant-free spermatozoa in heterozygous carriers of the CFTR-variant using flow cytometry (FC). Using FC and sorting, single cell polymerase chain reaction, immuno-fluorescent staining an experimental study was performed on nine fertile semen donors and three heterozygous infertile men carrying the Phe508del gene variant. Chemical inhibition of CFTR interfered with sperm capacitation. Most viable spermatozoa of heterozygous carriers of the Phe508del variant of the CFTR-gene show immune-fluorescent CFTR. Sperm capacitation in Phe508del carriers was similar to that in healthy semen donors. Distribution of the Phe508del allele in trio data of CF-affected families corresponded to the expected recessive inheritance pattern. Infertility in Phe508del heterozygous men is unlikely to be caused by the pathogenic variant although some contribution cannot be excluded. Normal sperm capacitation in carriers of pathogenic variants of the Phe508del-gene may in part explain the high prevalence of a potentially lethal recessive disorder.

CFTR gene variants as a reason for impaired spermatogenesis: a pilot study and a Meta-analysis of published data

There is increasing data that IVS8-5T variand and TG repeats could lead to impaired spermatogenesis. To investigate this we performed Sanger sequencing on 50 Bulgarian men with a sperm count below 5 × 10⁶/mL and 20 normal fertile men. Frequencies of the results were compared among the two groups. A meta-analysis was perfomed by using the data for 6,423 patients and 5,834 control subjects, tested for the IVS8-5T polymorphism. One case subject (2.0%) was homozygote for the 5 T/5T variant whereas two (4.0%) were heterozygotes for the 5 T/7T variant. No 5 T alleles were found in the control group. The genotypes of the two groups showed a statistically significant difference (p = 0.04, α < 0.05). Also, the odds ratio was 3.73, but this was unsignificant (p = 0.38). All control subjects had 11 TG repeats and for the test group: 47 (94.0%) men with 11 TG repeats and three (6.00%) with 10 TG repeats. Fisher's test showed no significant difference (p = 0.55). The meta-analysis showed that IVS8-5T variant was a risk factor for impaired spermatogenesis (OR = 2.84, p < 0.05) and this was more prominent for non-European (OR = 4.50, p < 0.05) compared to European (OR = 1.28, p < 0.05) men. The IVS8 - 5 T variant could be associated with disorders of sperm production.

CFTR gene mutations and polymorphism are associated with non-obstructive azoospermia: From case-control study

A variety of experimental studies have yielded evidence that the cystic fibrosis transmembrane conductance regulator (CFTR) protein participates in the process of spermatogenesis. However, the association between CFTR gene and non-obstructive azoospermia (NOA) disease remained to be a question. First, we reviewed available data from the PubMed and Embase databases before May 2016 to find the most common mutations of CFTR gene in NOA patients. Second, an original case-control study was conducted on NOA patients (n=100) and a control group consisting of fertile males (n=100), selected from August 2015 to March 2017, to detect CFTR gene mutations and polymorphism. Peripheral blood samples from NOA patients and normal controls were analyzed for the presence of specific sequences of CFTR gene by polymerase chain reaction amplification followed by direct sequencing. From our comprehensive review, 12 case-control studies were found concerning the relation between CFTR gene mutations and polymorphism and NOA disease. Fifty-four mutations were mentioned and IVS8 poly-T, TG repeats, F508del and R117H mutations were the most common ones. Based on that, we detected IVS8 poly-T, TG repeats, F508del, R117H and M470V mutations in our case control study. We found that the T5 allele was present at a significantly higher rate in NOA patients than in the control group (5.00% versus 0.00%, p<0.01) with increased risk having NOA [Odds ratios (OR) 2.05, 95% confidence intervals (CI) 1.85-2.27]. The T5 variant was always accompanied by TG12 (10/10) and V470 allele participated in most TG12T5 haplotypes (8/10). TG12T5-V470 haplotype also enhanced risk of having NOA [OR 2.04, 95% CI 1.84-2.26]. F508del and R117H mutations were not found in either group. In conclusion, the polyvariant mutant genes of CFTR: T5 allele and TG12-T5-V470 genotype are correlated with NOA, but F508del and R117H mutations have low possibility to be associated with NOA.

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.

Novel regulators of spermatogenesis

Spermatogenesis is a multistep process that supports the production of millions of sperm daily. Understanding of the molecular mechanisms that regulate spermatogenesis has been a major focus for decades. Yet, the regulators involved in different cellular processes of spermatogenesis remain largely unknown. Human diseases that result in defective spermatogenesis have provided hints on the molecular mechanisms regulating this process. In this review, we have summarized recent findings on the function and signaling mechanisms of several genes that are known to be associated with disease or pathological processes, including CFTR, CD147, YWK-II and CT genes, and discuss their potential roles in regulating different processes of spermatogenesis.

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.

CFTR mutations in men with congenital bilateral absence of the vas deferens (CBAVD): a systemic review and meta-analysis

BACKGROUND

Numerous studies have reported CFTR mutations in CBAVD (congenital bilateral absence of the vas deferens) patients, but their results are not completely consistent. Here, we present a systemic review and meta-analysis with emphasis on clarifying further the genetic association of CFTR mutations with CBAVD.

METHODS

We searched the MEDLINE database until March, 2011 for eligible articles reporting CFTR mutations in CBAVD. Relevant data from each included study were abstracted by two independent reviewers. The overall frequency of CFTR mutations in CBAVD and the odds ratio (OR) for common specific alleles were pooled under random-effect or fixed-effect model as appropriate. Subgroup analysis was performed by ethnicity, and potential heterogeneity and bias were both assessed.

RESULTS

Among CBAVD patients, 78% had at least one CFTR mutation, 46% having two and 28% only one. Moreover, the common heterozygous F508del/5T and F508del/R117H were observed in 17 and 4% of CBAVD cases respectively, and the allele frequency in CBAVD was 17% for F508del, 25% for 5T and 3% for R117H. Subgroup analysis indicated an increased frequency of cases with two mutations in Caucasian patients than in Non-Caucasian (68 versus 50%, P= 0.012), but no differences for cases with at least one mutation (88 versus 77%, P= 0.163) or with only one mutation (17 versus 25%, P= 0.115). Caucasian patients had higher F508del frequency, but lower 5T frequency, than Non-Caucasian (22 versus 8%, P= 0.001; 20 versus 31%, P= 0.009). Summary OR was 9.25 for 5T [95% confidence interval (CI) 7.07-12.11, P= 0.000], with moderate heterogeneity (I(2)= 49.20%, P= 0.019) and evident bias (Egger's test, P= 0.005), and it was 19.43 for 5T/(TG)12_13 (95% CI 10.48-30.03, P= 0.000) without any evidence of heterogeneity (I(2)= 0.1%, P= 0.391) and bias (Egger's test, P= 0.160). The OR for 5T/(TG)12_13 was significantly higher than that for 5T allele (P= 0.000).

CONCLUSIONS

In summary, our results demonstrate a high frequency of CFTR mutations in CBAVD patients, and these exhibit evident ethnic differences. In addition, 5T allele and 5T/(TG)12_13 may contribute to the increased risk for CBAVD, with the 5T penetrance probably being modulated by adjacent (TG)12_13.

The decline of fertility in male uremic patients is correlated with low expression of the cystic fibrosis transmembrane conductance regulator protein (CFTR) in human sperm

BACKGROUND

The present study was designed to investigate the possible association between infertility of male uremic patients and expression of the cystic fibrosis transmembrane conductance regulator (CFTR) protein in their sperm.

METHODS

Semen was collected and analyzed. Serum levels of FSH, LH and testosterone were measured by radioimmunoassay. The sperm CFTR expressions of 21 uremic patients and 15 renal transplant patients were measured and compared with those of 32 healthy and 33 infertile men.

RESULTS

Only 9 ± 5.9% of sperm from uremic patients expressed CFTR, significantly less than those of the renal transplant patients (29 ± 14.3%, P< 0.001), the infertile men (42 ± 20.7%, P< 0.001) and the healthy men (51 ± 20.5%, P< 0.001). Furthermore, significantly fewer sperm from renal transplant patients expressed CFTR than those of the infertile men (P< 0.05) and the healthy men (P< 0.01). LH levels in uremic patients were significantly higher than in all other groups, whereas FSH levels in uremic patients were only significantly higher than in infertile and healthy men. There was no significant difference in testosterone level among the four categories.

CONCLUSIONS

Sperm CFTR expression is depressed in uremic patients but recovers to some degree after renal transplant along with some improvement in fertility, indicating a 'reversible' change. These results suggest that the CFTR expression rate in sperm is correlated with the decline of uremic patients' fertility, and may be considered as a potential marker to assess the fertility of male uremic patients.

Recommendations for the classification of diseases as CFTR-related disorders

Several diseases have been clinically or genetically related to cystic fibrosis (CF), but a consensus definition is lacking. Here, we present a proposal for consensus guidelines on cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (CFTR-RDs), reached after expert discussion and two dedicated workshops. A CFTR-RD may be defined as "a clinical entity associated with CFTR dysfunction that does not fulfil diagnostic criteria for CF". The utility of sweat testing, mutation analysis, nasal potential difference, and/or intestinal current measurement for the differential diagnosis of CF and CFTR-RD is discussed. Algorithms which use genetic and functional diagnostic tests to distinguish CF and CFTR-RDs are presented. According to present knowledge, congenital bilateral absence of vas deferens (CBAVD), acute recurrent or chronic pancreatitis and disseminated bronchiectasis, all with CFTR dysfunction, are CFTR-RDs.

Defective CFTR-dependent CREB activation results in impaired spermatogenesis and azoospermia

Cystic fibrosis (CF) is the most common life-limiting recessive genetic disease among Caucasians caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) with over 95% male patients infertile. However, whether CFTR mutations could affect spermatogenesis and result in azoospermia remains an open question. Here we report compromised spermatogenesis, with significantly reduced testicular weight and sperm count, and decreased cAMP-responsive element binding protein (CREB) expression in the testes of CFTR knockout mice. The involvement of CFTR in HCO₃⁻ transport and the expression of the HCO₃⁻ sensor, soluble adenylyl cyclase (sAC), are demonstrated for the first time in the primary culture of rat Sertoli cells. Inhibition of CFTR or depletion of HCO₃⁻ could reduce FSH-stimulated, sAC-dependent cAMP production and phosphorylation of CREB, the key transcription factor in spermatogenesis. Decreased CFTR and CREB expression are also observed in human testes with azoospermia. The present study reveals a previously undefined role of CFTR and sAC in regulating the cAMP-CREB signaling pathway in Sertoli cells, defect of which may result in impaired spermatogenesis and azoospermia. Altered CFTR-sAC-cAMP-CREB functional loop may also underline the pathogenesis of various CF-related diseases.

Association of genetic variants in CFTR gene, IVS8 c.1210-12T[5_9] and c.1210-35_1210-12GT[8_12], with spermatogenetic failure: case-control study and meta-analysis

It has been proposed that the genetic variants of IVS8 c.1210-12T[5_9] and adjacent c.1210-35_1210-12GT[8_12] in cystic fibrosis transmembrane conductance regulator gene might contribute to the spermatogenetic failure, but numerous genetic association studies that aimed to test this hypothesis reported conflicting results. So, in order to clarify such inconsistencies, we first conducted an original case-control study in Chinese Han population that consisted of 126 non-obstructive azoospermia, 169 severe oligospermia and 213 fertile male controls, and subsequently performed a meta-analysis of the available data, including our results. Our case-control study revealed that the frequencies of the T[5] allele and the T[5]+GT[12] combination in patients with non-obstructive azoospermia were both significantly higher than those in the fertile controls (13.1 versus 2.8%, P<0.01; 97.0 versus 41.7%, P<0.01, respectively), thus indicating a high risk susceptibility to non-obstructive azoospermia for males with T[5] allele or T[5]+GT[12]. However, as for the patients with severe oligospermia, both the T[5] allele frequency and T[5]+GT[12] did not differ from that for the control subjects (4.4 versus 2.8%, P>0.01; 53.3 versus 41.7%, P>0.01, respectively). In addition, our meta-analysis showed a significant increased risk of non-obstructive azoospermia for males with T[5] allele [odds ratio (OR) 3.45, 95% confidence intervals (CI) 2.29-5.20, P=0.000] and T[5]+GT[12] (OR 7.57, 95% CI 2.53-22.65, P=0.000) compared with males carrying other alleles. By contrast, neither T[5] allele itself nor T[5]+GT[12] combination had any effects on the risk of severe oligospermia (OR 0.96, 95% CI 0.42-2.21, P=0.002; OR 1.33, 95% CI 0.64-2.76, P=0.447). On the basis of these results, it can be concluded that the T[5] allele itself, or in combination with GT[12] repeat, may increase the susceptibility risk of non-obstructive azoospermia, but not that of severe oligospermia.

All azoospermic males should be screened for cystic fibrosis mutations before intracytoplasmic sperm injection

We assessed the frequency of CFTR mutations in groups with varying degrees of sub-fertility and compared these groups to a fertile male group with proven paternity. Screening for CFTR mutations should be routine for all azoospermic males, irrespective of obstructive or non-obstructive etiology, prior to proposing ICSI treatment. CFTR testing has no value in the investigation of non-azoospermic infertile males.

CFTR is essential for sperm fertilizing capacity and is correlated with sperm quality in humans

BACKGROUND

Our previous studies have demonstrated the cystic fibrosis transmembrane conductance regulator (CFTR) is important for capacitation and male fertility in mouse and guinea pig spermatozoa. However, the exact function of CFTR on human sperm fertilizing capacity, and correlation with sperm quality has not been established. The present study may shed light on some unexplained male infertility, and on a possible new method for diagnosis of male infertility and strategy for male contraception.

METHODS

To assess the effect of CFTR on human sperm fertilizing capacity, we examined sperm capacitation and the acrosome reaction using chlortetracycline staining, analyzed sperm hyperactivation by computer-assisted semen analysis (CASA), measured intracellular cAMP levels using ElA and evaluated sperm penetration of zona-free hamster eggs assay in fertile men. The percentage of spermatozoa expressing CFTR from fertile, healthy and infertile men (mainly teratospermic, asthenoteratospermic, asthenospermic and oligospermic) was conducted by indirect immunofluorescence staining.

RESULTS

Progesterone significantly facilitated human sperm capacitation and ZP3 triggered the acrosome reaction, both were significantly inhibited by CFTR inhibitor-172 (CFTRinh-172; 10 nM-1 microM) in a dose-dependent manner. The presence of 100 nM CFTRinh-172 markedly depressed intracellular cAMP levels, sperm hyperactivation and sperm penetration of zona-free hamster eggs. In addition, the percentage of spermatozoa expressing CFTR in the fertile men was significantly higher than healthy and infertile men categories (P < 0.01).

CONCLUSIONS

CFTR is essential for human sperm fertilizing capacity and the impairment of CFTR expression in spermatozoa is correlated with a reduction of sperm quality. These results suggest that defective expression of CFTR in human sperm may lead to the reduction of sperm fertilizing capacity.

Genetic characterization of two 46,XX males without gonadal ambiguities

PURPOSE

To evaluate hypotheses which explain phenotypic variability in sex determining region Y positive 46,XX males. We investigate two 46,XX males without gonadal ambiguities.

METHODS

Cytogenetic and molecular analyses were used to identify the presence of Y chromosome material and to map the translocation breakpoint. Finally, the pattern of X chromosome inactivation was studied using the methylation assay at the androgen receptor locus.

RESULTS

The presence of Y chromosome material, including the sex determining region Y gene, was demonstrated in both men. However, the amount of translocated Y chromosome material differed between the patients. Different X chromosome inactivation patterns were found in the patients; random in one patient and non-random in the other.

CONCLUSIONS

We found a lack of association between phenotype and X chromosome inactivation pattern. Our cytogenetic and molecular analyses show support for the position effect hypothesis explaining the phenotypic variability in XX males.

Critical role of CFTR in uterine bicarbonate secretion and the fertilizing capacity of sperm

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated Cl- channel expressed in a wide variety of epithelial cells, mutations of which are responsible for hallmark defective Cl- and HCO3- secretion seen in cystic fibrosis (CF). However, the physiological role of CFTR in reproductive tracts is far from understood although infertility has been observed in CF patients of both sexes. Previously we have demonstrated the expression of CFTR in the female reproductive tract and the involvement of CFTR in mediating anion secretion by the endometrium. Our recent results show that endometrial epithelial cells possess a cAMP-activated HCO3- transport mechanism, which could be impaired with channel blockers known to block CFTR or antisense against CFTR. Co-culture of sperm with CFTR antisense-treated endometrial cells or HCO3- secretion-defective CF epithelial cells resulted in reduced sperm capacitation and egg-fertilizing ability. Addition of HCO3- to the culture media and transfection of wild-type CFTR into CF cells rescued the fertilizing capacity of sperm. Immunostaining and Western blot revealed that CFTR is expressed in rodent sperm and intracellular measurement of pH during sperm capacitation indicated that the entry of HCO3- into sperm could be inhibited by CFTR inhibitor. These results are consistent with a critical role of CFTR in controlling uterine HCO3- secretion and sperm fertilizing capacity, suggesting that CFTR may be a potential target for post-meiotic regulation of fertility.

Increased frequency of cystic fibrosis transmembrane conductance regulator gene mutations in infertile males

OBJECTIVE

To investigate the frequency of mutations of the cystic fibrosis transmembrane regulator (CFTR) gene in males with reduced sperm quality before intracytoplasmic sperm injection (ICSI).

DESIGN

The nine most frequent cystic-fibrosis-causing mutations in the German population and IVS8T alleles were analyzed.

SETTING

University-based centers for reproductive medicine and clinical genetics.

PATIENT(S)

An unselected group of 597 males with oligo-, astheno-, terato-, crypto-, oligoasthenoteratozoospermia, or azoospermia, which underwent pre-ICSI genetic counseling over a 5-year period.

INTERVENTION(S)

Blood samples were collected from the patients during genetic counseling.

MAIN OUTCOME MEASURE(S)

Frequency of mutations of CFTR gene in infertile males.

RESULT(S)

A heterozygous CFTR mutation was observed in 34 of 597 patients (5.70%). None of the patients had two CFTR mutations. Given that our mutation panel recognizes about 82% of heterozygotes, it can be assumed that the frequency of CFTR heterozygotes in our cohort is about 6.94%. The frequency of CFTR mutations in our cohort did not correlate with a reduced sperm count.

CONCLUSION(S)

The frequency of cystic fibrosis in the German population is 1:3300. Thus, a CFTR heterozygosity of 3.42% can be estimated. This indicates that in our cohort of infertile males, the frequency of CFTR heterozygosity is twofold higher than in the general population (P<.0001).

Molecular evaluation of CFTR sequence variants in male infertility of testicular origin

Although the involvement of the CFTR gene has been well established in congenital agenesia of vas deferens, its role in non-obstructive (NOb) infertility is still a matter of debate. In order to definitively define the involvement of the CFTR gene in spermatogenic impairment and a potential synergistic contribution to known genetic and clinical factors, genetic variants in the entire coding sequence and the immediately flanking regions of the CFTR gene, along with a thorough clinical evaluation, were analysed in 83 NOb infertile patients and 87 clinically well-defined fertile individuals as controls. The results of our study showed no statistical difference between CFTR carrier frequency in the infertile and fertile population. Specifically, the IVS8-6(5T) allele carrier frequency was similar in NOb infertile patients when compared with fertile men, but it is noteworthy that, when fertile men were classified into having optimal and suboptimal fertility, no 5T allele was found among the 35 men with optimal fertility parameters. In conclusion, extensive CFTR analysis in infertile individuals and fertile population as adequate control definitively excludes the involvement of the CFTR gene variants in sperm production and stresses the importance of carefully identifying those individuals with obstructive defects, in whom CFTR screening will be beneficial.

Paracentric inversion of chromosome 7(q22-31) associated with nonobstructive azoospermia

OBJECTIVE

To examine an unusual paracentric inversion of chromosome 7 found in an azoospermic man.

DESIGN

Case report.

SETTING

Infertility clinic at a private hospital.

PATIENT(S)

An azoospermic but otherwise apparently healthy man.

INTERVENTION(S)

Karyotyping with peripheral blood lymphocytes, microdissection testicular sperm extraction (TESE), and intracytoplasmic sperm injection (ICSI).

MAIN OUTCOME MEASURE(S)

Sperm count and GBG banding.

RESULTS

A karyogram revealed paracentric inversion of chromosome 7 with breakpoints at 7q22 and 7q31. Testicular histopathology confirmed the Sertoli cell-only syndrome. Successful pregnancy and delivery were achieved with microdissection TESE and ICSI.

CONCLUSION(S)

Paracentric inversion of chromosome 7(q22-31) associated with nonobstructive azoospermia is rare. Chromosome 7q22-31 may be responsible for impaired spermatogenesis.

Molecular pathology of the CFTR locus in male infertility

Congenital bilateral absence of the vas deferens (CBAVD) is a form of infertility with an autosomal recessive genetic background in otherwise healthy males. CBAVD is caused by cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations on both alleles in approximately 80% of cases. Striking CFTR genotypic differences are observed in cystic fibrosis (CF) and in CBAVD. The 5T allele is a CBAVD mutation with incomplete penetrance. Recent evidence confirmed that a second polymorphic locus exists and is a major CFTR modifier. The development of minigene models have led to results suggesting that CFTR exon 9 is skipped in humans because of unusual suboptimal 5' splice sites. An extremely rare T3 allele has been reported and it has recently been confirmed that the T3 allele dramatically increases exon 9 skipping and should be considered as a 'CF' mutation. Routine testing for the most prevalent mutations in the CF Caucasian population will miss most CFTR gene alterations, which can be detected only through exhaustive scanning of CFTR sequences. Finally, a higher than expected frequency of CFTR mutations and/or polymorphisms is now found in a growing number of monosymptomatic disorders, which creates a dilemma for setting nosologic boundaries between CF and diseases related to CFTR.

High frequency of (TG)mTn variant tracts in the cystic fibrosis transmembrane conductance regulator gene in men with high semen viscosity

OBJECTIVE

To evaluate a possible correlation between abnormal semen consistency and cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations and variant tracts.

DESIGN

Study of CFTR mutations and variant tracts in men with high semen viscosity as compared with normospermic men.

SETTING

University-based centers for andrology, clinical biochemistry, and cystic fibrosis.

PATIENT(S)

Forty-six male partners from infertile couples with sine causa high semen viscosity compared with 72 normospermic men.

INTERVENTION(S)

Semen sample collection.

MAIN OUTCOME MEASURE(S)

We obtained the (TG)mTn polymorphic tracts and a panel of 31 mutations of CFTR, semen viscosity, and semen variables.

RESULT(S)

The frequencies of the (TG)12 and T5 variant alleles were statistically significantly higher in men with high semen viscosity (17.4% and 7.6%, respectively) than in the normospermic control group (6.9% and 1.4%, respectively). The frequency of the genotypes carrying (TG)12 or T5 was statistically significantly higher in men with high semen viscosity (39.1%) than in the normospermic control group (16.7%). Four men with high semen viscosity showed the variant (TG)12T5 haplotype; one of these men presented variant tracts on both alleles. None of the normospermic controls showed a (TG)12T5 haplotype.

CONCLUSION(S)

Semen hyperviscosity could be considered a "minimal clinical expression" of cystic fibrosis; CFTR gene sequence variations may constitute the genetic basis for this disease.