Heterogeneity for mutations in the CFTR gene and clinical correlations in patients with congenital absence of the vas deferens

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.

Pathogenic Variants and Genotypes of the CFTR Gene in Russian Men with Cystic Fibrosis and CBAVD Syndrome

Pathogenic CFTR variants cause cystic fibrosis (CF), and CF-related disorders (CF-RD), including bilateral aplasia of the vas deferens (CBAVD). The spectrum of clinical manifestations depends on the CFTR genotype. The frequency and spectrum of the CFTR variants vary between populations and clinical groups. CFTR variants and genotypes were analyzed in Russian men with CF (n = 546) and CBAVD syndrome (n = 125). Pathogenic variants were detected in 93.95% and 39.2% of the CF and CBAVD alleles, respectively. The most frequent c.1521_1523del (F508del; p.Phe508del) variant was found in 541 (49.5%) CF alleles. A total of 162 CFTR genotypes were revealed in CF patients, including 152 homozygous and 394 compound-heterozygous. The most common CF-genotype was F508del/F508del (24.9%). Other frequent CF-genotypes were F508del/3849+10kbC>T, F508del/CFTRdele2,3, and F508del/E92K. CF-causing variants and/or 5T allele were found in 88% of CBAVD patients: 5T/CFTRmut (48.0%), CFTRmut/N (17.6%), CFTRmut/CFTRmut (6.4%), 5T/5T (10.4%), 5T/N (5.6%) and N/N (12.0%), with the most common CBAVD-genotype being F508del/5T (29.6%). The allele frequencies of F508del, CFTRdele2,3 394delTT, and 3849+10kbC>T were significantly higher in CF patients. L138ins/L138ins, 2184insA/E92K, and L138ins/N genotypes were found in CBAVD, but not in CF patients. The results indicate certain differences in the frequency of some CFTR variants and genotypes in Russian CF and CBAVD patients.

Whole Exome Sequencing Identifies a Rare CFTR Mutation in Brothers With Anomalies of the Vas Deferens: A Case Study

Congenital bilateral absence of the vas deferens (CBAVD) occurs in almost all men with cystic fibrosis. Prevailing theories on this pathophysiology relate to pathogenic mutations in the cystic fibrosis transmembrane regulator gene leading to agenesis or obliteration of vas deferens in utero. In this study, we present a case of two brothers with congenital anomalies of the vas deferens who were found to have carried a rare, heterozygous cystic fibrosis transmembrane regulator variant p.r347h without pulmonary or gastrointestinal signs or symptoms of cystic fibrosis .

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.

Analysis of the genotypic profile and its relationship with the clinical manifestations in people with cystic fibrosis: study from a rare disease registry

Background

Cystic fibrosis (CF) has a vast and heterogeneous mutational spectrum in Europe. This variability has also been described in Spain, and there are numerous studies linking CFTR variants with the symptoms of the disease. Most of the studies analysed determinate clinical manifestations or specific sequence variants in patients from clinical units. Others used registry data without addressing the genotype–phenotype relationship. Therefore, the objective of this study is to describe the genetic and clinical characteristics of people with CF and to analyse the relationship between both using data from the rare disease registry of a region in southeastern Spain.

Methods

A cross-sectional study was carried out in people with a confirmed diagnosis of CF registered in the Rare Diseases Information System (SIER) of the Region of Murcia (Spain). The patients were classified into two genotypes according to the functional consequence that the genetic variants had on the CFTR protein.

Results

There were 192 people diagnosed with CF reported in the Region of Murcia as of 31 December 2018. Seventy-six genotypes and 49 different variants were described, with c.1521_1523delCTT (p. Phe508del) being the most common in 58.3% of the CF patients and 37.0% of the alleles. In addition, 67% of the patients were classified as a high-risk genotype, which was associated with a lower percentage of FEV₁ (OR: 5.3; 95% CI: 1.2, 24.4), an increased risk of colonization by Pseudomonas aeruginosa (OR: 7.5; 95% CI: 1.7, 33.0) and the presence of pancreatic insufficiency (OR: 28.1; 95% CI: 9.3, 84.4) compared to those with a low-risk genotype.

Conclusions

This is the first study in Spain that describes the mutational spectrum and its association with clinical manifestations in patients with CF using data from a rare disease registry. The results obtained allow planning for the health resources needed by people with this disease, thus contributing to the development of personalized medicine that helps to optimize health care in CF patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02373-y.

Congenital Bilateral Absence of the Vas Deferens

Congenital bilateral absence of the vas deferens (CBAVD) is clinically characterized by the absence of the bilateral vas deferens; the main clinical manifestation is infertility, accounting for 1–2% of male infertility cases. CBAVD may be accompanied by congenital abnormalities in the urogenital system and cystic fibrosis (CF)-related clinical manifestations. CBAVD can develop as a mild manifestation of CF or can be isolated. The main pathogenic mechanism of CBAVD is gene mutation, and CBAVD and CF have a common genetic mutation background. CFTR mutation is the main pathogenic cause of CBAVD and CF, and ADGRG2 mutation is the second most common cause. Although lack of the vas deferens in CBAVD patients causes infertility due to the inability to release sperm, the testes of CBAVD patients have spermatogenic function. Therefore, CBAVD patients can achieve fertility through sperm retrieval surgery and assisted reproductive technology (ART). However, gene mutations in CBAVD patients can have an impact on the ART outcome, and there is a risk of passing on gene mutations to offspring. For CBAVD patients and their spouses, performing genetic counseling (which currently refers mainly to CFTR mutation screening) helps to reduce the risks of genetic mutations being passed on to offspring and of offspring having CF with concomitant CBAVD.

A patient with 47, XYY mosaic karyotype and congenital absence of bilateral vas deferens: a case report and literature review

Background

The incidence of 47, XYY syndrome in live-born male infants is 1/1000. Due to its variable clinical symptoms, the diagnosis is easy to miss. The incidence of congenital bilateral absence of the vas deferens (CBAVD) in infertile men is 1–2%. The main cause is the mutation of CFTR and ADGAG2 genes.

Case presentation

The patient was a 33-year-old man who visited a doctor 5 years ago due to infertility. The investigation revealed that the patient’s secondary sexual characteristics, testicular, and penis development were normal, and there was no gynecomastia, but the bilateral vas deferens and epididymis were not palpable. Transrectal ultrasound showed that the left seminal vesicle was missing, and the right seminal vesicle was atrophied. No abnormality was observed in Y chromosome microdeletion. Karyotype analysis indicated that the patient was 46, XY/47, XYY mosaic. Genetic testing found heterozygous mutations at two sites of CFTR (c263T > G and c2249C > T).

Conclusions

Herein, we report the rare case of a male patient with clinical manifestations of infertility, chromosome 46, XY/47, XXY mosaic type, simultaneously manifested as the absence of bilateral vas deferens. Two pathogenic heterozygous CFTR gene mutations were found. Given the low genetic risk of the disease, we recommend that patients undergo intracytoplasmic sperm injection (ICSI) for fertility assessment.

Incidental finding of a congenital unilateral absence of the vas deferens during robotic inguinal hernia repair: missing a crucial landmark. A case report

INTRODUCTION

We report on a case of congenital unilateral atresia of the vas deferens encountered during a robotic-assisted transabdominal preperitoneal (TAPP) inguinal hernia repair.

CASE REPORT

Our 65-years-old male patient was scheduled for a bilateral robotic-assisted TAPP inguinal hernia repair because of bilateral symptomatic groin hernia. Standard intraoperative dissection obtaining a critical view of the myopectineal orifice did not allow for an identification of the vas deferens (VD) on the left side. On the right side, a normal VD was identified. There was no suspicion of an intraoperative lesion or ligation of the VD. Both gonadal and inferior epigastric vessels were present on both sides. Upon clinical evaluation, no VD was palpable in the scrotum on the left side. The diagnosis of a congenital unilateral absence of the vas deferens was made. Additional abdominal computed tomography scan revealed a congenital agenesis of the left kidney, ureter, vesicula seminalis and vas deferens.

DISCUSSION

The accidental finding of a congenital absence of the vas deferens during inguinal hernia repair is rare. However, surgeons performing inguinal hernia repair should be aware of this condition and the clinical implications it poses, as this could prevent unnecessary exploration and missed diagnosis of associated underlying conditions.

Probability of high-risk genetic matching with oocyte and semen donors: complete gene analysis or genotyping test?

PURPOSE

To estimate the probability of high-risk genetic matching when assisted reproductive techniques (ART) are applied with double gamete donation, following an NGS carrier test based on a complete study of the genes concerned. We then determine the results that would have been obtained if the genotyping tests most widely used in Spanish gamete banks had been applied.

METHODS

In this descriptive observational study, 1818 gamete donors were characterised by NGS. The pathogenic variants detected were analysed to estimate the probability of high-risk genetic matching and to determine the results that would have been obtained if the three most commonly used genotyping tests in ART had been applied.

RESULTS

The probability of high-risk genetic matching with gamete donation, screened by NGS and complete gene analysis, was 5.5%, versus the 0.6-2.7% that would have been obtained with the genotyping test. A total of 1741 variants were detected, including 607 different variants, of which only 22.6% would have been detected by all three genotyping tests considered and 44.7% of which would not have been detected by any of these tests.

CONCLUSION

Our study highlights the considerable heterogeneity of the genotyping tests, which present significant differences in their ability to detect pathogenic variants. The complete study of the genes by NGS considerably reduces reproductive risks when genetic matching is performed with gamete donors. Accordingly, we recommend that carrier screening in gamete donors be carried out using NGS and a complete study with nontargeted analysis of the variants of the screened genes.

Genetic mutation analysis of 22 patients with congenital absence of vas deferens: A single-center study†

Congenital absence of the vas deferens (CAVD), a congenital malformation of the male reproductive system, causes obstructive azoospermia and male infertility. Currently, the cystic fibrosis transmembrane conductance regulator (CFTR) has been recognized as the main pathogenic gene in CAVD, with some other genes, such as adhesion G-protein coupled receptor G2 (ADGRG2), solute carrier family 9 isoform 3 (SLC9A3), sodium channel epithelial 1 subunit beta (SCNN1B), and carbonic anhydrase 12 (CA12) being candidate genes in the pathogenesis of CAVD. However, the frequency and spectrum of these mutations, as well as the pathogenic mechanisms of CAVD, have not been fully investigated. Here, we sequenced all genes with potentially pathogenic mutations using next-generation sequencing and verified all identified variants by Sanger sequencing. Further bioinformatic analysis was performed to predict the pathogenicity of mutations. We described the distribution of the p.V470M, poly-T, and TG-repeat CFTR polymorphisms, and identified novel missense mutations in the CFTR and SLC9A3 genes, respectively. Taken together, we identified mutations in the CFTR, ADGRG2, SLC9A3, SCNN1B, and CA12 genes in 22 patients with CAVD, thus broadening the genetic spectrum of Chinese patients with CAVD.

Development of a multivariable prediction model for congenital unilateral absence of the vas deferens in male partners of infertile couples

BACKGROUND

Congenital unilateral absence of vas deferens has been diagnosed in fertile and normozoospermic males and is associated with the risk of unilateral renal absence or cystic fibrosis transmembrane conductance regulator mutations; but no prediction model currently exists to diagnose this condition.

OBJECTIVES

The study aims to identify clinical and biological variables that may have a predictive value for the diagnosis of congenital unilateral absence of vas deferens in male partners of infertile couples MATERIALS AND METHODS: We designed a retrospective, cross-sectional, case-control study on electronic health records of a single tertiary-care andrological centre collected between 1998 and 2018. We included all subjects diagnosed with congenital unilateral absence of vas deferens using combined scrotal and transrectal ultrasounds. Controls were confirmed free of congenital unilateral absence of vas deferens by the same way. Both groups received standardised exploration procedures. Multivariable logistic regression model was built in a backward stepwise manner. Model performance and calibration were assessed. The study is reported according to TRIPOD statement.

RESULTS

We included 69 congenital unilateral absence of vas deferens cases and 78 controls. Cases had a lower semen volume than controls. The congenital unilateral absence of vas deferens risk was associated with history of cryptorchidism and both levels of semen fructose and α-glucosidase. These predictors were confirmed by a random forest algorithm. The area under the curve was 0.886 (95% interval: 0.81-0.92). Calibration was performed with the Hosmer-Lemeshow test (p = 0.88).

DISCUSSION AND CONCLUSION

History of cryptorchidism, semen fructose and α-glucosidase were identified as relevant and independent predictors for the diagnosis of congenital unilateral absence of vas deferens. The model enables to identify male patients with a high risk of congenital unilateral absence of vas deferens to whom a transrectal ultrasounds would be proposed to confirm the diagnosis, whatever their semen parameters. It will also help to address the risks of unilateral renal absence and of cystic fibrosis transmembrane conductance regulator mutations carrying during the management of infertile couples.

Identification of pleiotropy at the gene level between psychiatric disorders and related traits

Major mental disorders are highly prevalent and make a substantial contribution to the global disease burden. It is known that mental disorders share clinical characteristics, and genome-wide association studies (GWASs) have recently provided evidence for shared genetic factors as well. Genetic overlaps are usually identified at the single-marker level. Here, we aimed to identify genetic overlaps at the gene level between 7 mental disorders (schizophrenia, autism spectrum disorder, major depressive disorder, anorexia nervosa, ADHD, bipolar disorder and anxiety), 8 brain morphometric traits, 2 cognitive traits (educational attainment and general cognitive function) and 9 personality traits (subjective well-being, depressive symptoms, neuroticism, extraversion, openness to experience, agreeableness and conscientiousness, children's aggressive behaviour, loneliness) based on publicly available GWASs. We performed systematic conditional regression analyses to identify independent signals and select loci associated with more than one trait. We identified 48 genes containing independent markers associated with several traits (pleiotropy at the gene level). We also report 9 genes with different markers that show independent associations with single traits (allelic heterogeneity). This study demonstrates that mental disorders and related traits do show pleiotropy at the gene level as well as the single-marker level. The identification of these genes might be important for prioritizing further deep genotyping, functional studies, or drug targeting.

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.

Congenital absence of the vas deferens: Cystic fibrosis transmembrane regulatory gene mutations

Congenital absence of the vas deferens (CAVD) is a rare genetic condition first discovered in the mid-18th century related to mutations in the cystic fibrosis transmembrane regulatory genes. The condition is typically found during work-up of male infertility, and the majority of cases can be diagnosed with complete history and physical examination and pertinent investigations. The condition can be separated into three subcategories, and genetic advances have led to a much better understanding behind the disease, its pathogenesis, and options for treatment. In this review, we discuss the genetics, pathogenesis, embryology, and diagnosis of treatment of CAVD. Future work in this area likely will aim to better understand the epigenetic factors that influence the development of the condition in order to identify potential upstream therapeutic targets.

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.

Carriers of cystic fibrosis among sperm donors: complete CFTR gene analysis versus CFTR genotyping

OBJECTIVE

To determine the frequency of cystic fibrosis (CF) carriers among sperm donors in Spain studied through a complete analysis of the CFTR gene and to compare the results with those that would have been obtained by the 4 genotyping panels of the CFTR gene most commonly used as a carrier test in the context of assisted reproduction in our country.

DESIGN

Descriptive observational study.

SETTING

Private center.

PATIENTS

Nine hundred thirty-five sperm donors, from January 2014 to June 2019.

INTERVENTION

None.

MAIN OUTCOME MEASURE

Presence of pathogenic variants in the CFTR gene.

RESULTS

17% of the donors were carriers of at least 1 pathogenic variant in CFTR, with 39 different pathogenic variants detected. Only 4 of these 39 variants (10.27%) would have been detected by the 4 genotyping tests considered, and 22 variants (56.41%) would not have been detected by any of the genotyping tests. The pathogenic variants of the CFTR gene included in the different genotyping tests analyzed vary widely, and <50% are common to all of them.

CONCLUSIONS

Although the was not based in the general population, these results show that the use of genotyping tests is associated with a high reproductive risk, because the rate of detection of CF carriers was lower when these panels were applied, in comparison with the complete study of the CFTR gene. We recommend that complete sequencing of the CFTR gene by next-generation sequencing be performed as a screening method for CF in sperm donors.

Genetics of the congenital absence of the vas deferens

Congenital absence of the vas deferens (CAVD) may have various clinical presentations depending on whether it is bilateral (CBAVD) or unilateral (CUAVD), complete or partial, and associated or not with other abnormalities of the male urogenital tract. CBAVD is usually discovered in adult men either during the systematic assessment of cystic fibrosis or other CFTR-related conditions, or during the exploration of isolated infertility with obstructive azoospermia. The prevalence of CAVDs in men is reported to be approximately 0.1%. However, this figure is probably underestimated, because unilateral forms of CAVD in asymptomatic fertile men are not usually diagnosed. The diagnosis of CAVDs is based on clinical, ultrasound, and sperm examinations. The majority of subjects with CAVD carry at least one cystic fibrosis-causing mutation that warrants CFTR testing and in case of a positive result, genetic counseling prior to conception. Approximately 2% of the cases of CAVD are hemizygous for a loss-of-function mutation in the ADGRG2 gene that may cause a familial form of X-linked infertility. However, despite this recent finding, 10–20% of CBAVDs and 60–70% of CUAVDs remain without a genetic diagnosis. An important proportion of these unexplained CAVDs coexist with a solitary kidney suggesting an early organogenesis disorder (Wolffian duct), unlike CAVDs related to CFTR or ADGRG2 mutations, which might be the result of progressive degeneration that begins later in fetal life and probably continues after birth. How the dysfunction of CFTR, ADGRG2, or other genes such as SLC29A3 leads to this involution is the subject of various pathophysiological hypotheses that are discussed in this review.

Male partners of infertile couples with congenital unilateral absence of the vas deferens are mainly non-azoospermic

BACKGROUND

Men with congenital unilateral absence of vas deferens were reported to be mainly azoospermic, with both unilateral renal absence and mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) but some have neither.

OBJECTIVES

To assess whether in infertile couples the male partners with congenital unilateral absence of vas deferens are mainly azoospermic men.

MATERIAL AND METHODS

Retrospective study in a unique university hospital; reproductive, clinical, CFTR analysis and seminal data of male partners of infertile couples (from 1998 to 2018) were analysed. Diagnosis of congenital unilateral absence of vas deferens was based on transrectal ultrasounds (TRUS): complete or partial absence of one vas deferens with complete contralateral vas deferens confirmed in 63 men. Distribution of sperm count in three classes: azoospermia, oligozoospermia or normozoospermia. Ultrasound determination of renal status; seminal biomarkers assays; and search for CFTR mutations.

RESULTS

Among the 63 men, 39.7% displayed azoospermia, 27% oligozoospermia and 33.3% normozoospermia; 42% of the non-azoospermic men (16/38) had previously obtained a natural pregnancy. We found unilateral renal absence in 17/59 patients (29%). Among 50 men with CFTR testing, five carried an allele associated with cystic fibrosis belonging to the 29 men without renal anomalies, indicating a high allelic frequency (8.6%). The 63 patients displayed high rates of surgical histories for undescended testicles or inguinal hernia, low values of semen volume and of total seminal glycerophosphocholine.

CONCLUSIONS

Our results indicate that men with congenital unilateral absence of vas deferens mainly display oligozoospermia or normozoospermia and that they were previously fertile. They clearly confirm, first, that CFTR testing is recommended in congenital unilateral absence of vas deferens men and it should be mandatory for those with normal kidneys; and, second, that TRUS is needed for the diagnosis of congenital unilateral absence of vas deferens. As congenital unilateral absence of vas deferens may be present whatever the sperm count, biological warnings are represented by semen volume and seminal epididymal markers and clinical warnings by surgical histories of undescended testes or inguinal hernia.

A rare frameshift variant in trans with the IVS9-5T allele of CFTR in a Chinese pedigree with congenital aplasia of vas deferens

PURPOSE

Congenital aplasia of vas deferens (CAVD) is an atypical form of cystic fibrosis (CF) and causes obstructive azoospermia and male infertility. Compound heterozygous variants of CFTR are the main cause of CAVD. However, most evidence comes from genetic screening of sporadic cases and little is from pedigree analysis. In this study, we performed analysis in a Chinese pedigree with two CAVD patients in order to determine the genetic cause of this familial disorder.

METHODS

In the present study, we performed whole-exome sequencing and co-segregation analysis in a Chinese pedigree involving two patients diagnosed with CAVD.

RESULTS

We identified a rare frameshift variant (NM_000492.3: c.50dupT;p.S18Qfs*27) and a frequent CBAVD-causing variant (IVS9-TG13-5T) in both patients. The frameshift variant introduced a premature termination codon and was not found in any public databases or reported in the literature. Co-segregation analysis confirmed these two variants were in compound heterozygous state. The other male members, who harbored the frameshift variant and benign IVS9-7T allele, did not have any typical clinical manifestations of CF or CAVD.

CONCLUSION

Our findings may broaden the mutation spectrum of CFTR in CAVD patients and provide more familial evidence that the combination of a mild variant and a severe variant in trans of CFTR can cause vas deferens malformation.

Genetics of male infertility

Male infertility is a multifactorial pathological condition affecting approximately 7% of the male population. The genetic landscape of male infertility is highly complex as semen and testis histological phenotypes are extremely heterogeneous, and at least 2,000 genes are involved in spermatogenesis. The highest frequency of known genetic factors contributing to male infertility (25%) is in azoospermia, but the number of identified genetic anomalies in other semen and aetiological categories is constantly growing. Genetic screening is relevant for its diagnostic value, clinical decision making, and appropriate genetic counselling. Anomalies in sex chromosomes have major roles in severe spermatogenic impairment. Autosome-linked gene mutations are mainly involved in central hypogonadism, monomorphic teratozoospermia or asthenozoospermia, congenital obstructive azoospermia, and familial cases of quantitative spermatogenic disturbances. Results from whole-genome association studies suggest a marginal role for common variants as causative factors; however, some of these variants can be important for pharmacogenetic purposes. Results of studies on copy number variations (CNVs) demonstrate a considerably higher CNV load in infertile patients than in normozoospermic men, whereas whole-exome analysis has proved to be a highly successful diagnostic tool in familial cases of male infertility. Despite such efforts, the aetiology of infertility remains unknown in about 40% of patients, and the discovery of novel genetic factors in idiopathic infertility is a major challenge for the field of androgenetics. Large, international, and consortium-based whole-exome and whole-genome studies are the most promising approach for the discovery of the missing genetic aetiology of idiopathic 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.

Congenital bilateral absence of the vas deferens as an atypical form of cystic fibrosis: reproductive implications and genetic counseling

Congenital bilateral absence of the vas deferens (CBAVD) is found in 1% to 2% of males with infertility and is present in 6% of obstructive azoospermia cases. Nearly 95% of men with cystic fibrosis (CF, an autosomal recessive disorder) have CBAVD. There are genetic links between CBAVD and CF. Some mutations in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR) can lead to CBAVD as a monosymptomatic form of CF. With the use of assisted reproductive techniques (ART), especially testicular or epididymal sperm aspiration, intracytoplasmic sperm injection, and in vitro fertilization, it is possible that men with CBAVD can produce offspring. Therefore, genetic counseling should be offered to couples undergoing ART to discuss the probability of having offspring that carry CFTR gene mutations. The aim of this review was to present the main cause of CBAVD, to call attention to its implications for assisted reproduction, and to show the importance of genetic counseling for couples where men have CBAVD, as they can have offspring with a lethal disease.

Congenital absence of vas deferens and ectopic kidney

INTRODUCTION

Congenital absence of the vas deferens (CUAVD) is a rare clinical entity, usually discovered accidently during surgical procedures of the urogenital zone, CUAVD has the prevalence of 0.5-1.0% in male population and it is associated with various forms of congenital genitourinary malformations like renal agenesis. we present a case of a 21 years old, male, managed in our private hospital for varicoceles and discovered to have CUAVD and ectopic kidney.

PRESENTATION OF CASE

A 21 years old male, with no significant medical or surgical history presented to our out-patient clinic complaining of scrotal heaviness and pain. upon physical examination he was discovered to have a bilateral varicocele and was scheduled for a bilateral varicocelectomy, during the procedure he was discovered with left side CUAVD.

DISCUSSION

Congenital unilateral absence of the vas deference is a very rare clinical entity in the male population it has an incidence of 0.5-1.0%. it is usually discovered during evaluation for infertility or surgical procedures of the urogenital zone. Unilateral congenital absence of the vas deference is more associated with renal agenesis (73.3%), compared to the bilateral form (11.8%)_. CAVD is responsible of 1-2% of male infertility.

CONCLUSION

Congenital absence of the vas deference is a unique clinical entity due to its great association with a large variety of urogenital abnormalities, we present this case to stress the importance of including scrotal examination in the routine physical exam to reduce the late diagnosis of such abnormality and it associated comorbidities.

New era of cystic fibrosis: Full mutational analysis and personalized therapy

Despite its apparently simple genetics, cystic fibrosis (CF) is a rather complex genetic disease. A lot of variability in the steps of the path from the cystic fibrosis transmembrane conductance regulator (CFTR) gene to the clinical manifestations originates an uncertain genotype - phenotype relationship. A major determinant of this uncertainty is the incomplete knowledge of the CFTR mutated genotypes, due to the high number of CFTR mutations and to the higher number of their combinations in trans and in cis. Also the very limited knowledge of functional effects of CFTR mutated alleles severely impairs our diagnostic and prognostic ability. The final phenotypic modulation exerted by CFTR modifier genes and interactome further complicates the framework. The next generation sequencing approach is a rapid, low-cost and high-throughput tool that allows a near complete structural characterization of CFTR mutated genotypes, as well as of genotypes of several other genes cooperating to the final CF clinical manifestations. This powerful method perfectly complements the new personalized therapeutic approach for CF. Drugs active on specific CFTR mutational classes are already available for CF patients or are in phase 3 trials. A complete genetic characterization has been becoming crucial for a correct personalized therapy. However, the need of a functional classification of each CFTR mutation potently arises. Future big efforts towards an ever more detailed knowledge of both structural and functional CFTR defects, coupled to parallel personalized therapeutic interventions decisive for CF cure can be foreseen.

Nationwide genetic analysis for molecularly unresolved cystic fibrosis patients in a multiethnic society: implications for preconception carrier screening

Background

Preconception carrier screening for cystic fibrosis (CF) is usually performed using ethnically targeted panels of selected mutations. This has been recently challenged by the use of expanded, ethnically indifferent, pan‐population panels. Israel is characterized by genetically heterogeneous populations carrying a wide range of CFTR mutations. To assess the potential of expanding the current Israeli preconception screening program, we sought the subset of molecularly unresolved CF patients listed in the Israeli CF data registry comprising ~650 patients.

Methods

An Israeli nationwide genotyping of 152 CF cases, representing 176 patients lacking molecular diagnosis, was conducted. Molecular analysis included Sanger sequencing for all exons and splice sites, multiplex ligation probe amplification (MLPA), and next‐generation sequencing of the poly‐T/TG tracts.

Results

We identified 54 different mutations, of which only 16 overlapped the 22 mutations included in the Israeli preconception screening program. A total of 29/54 (53.7%) mutations were already listed as CF causing by the CFTR2 database, and only 4/54 (7.4%) were novel. Molecular diagnosis was reached in 78/152 (51.3%) cases. Prenatal diagnosis of 24/78 (30.8%) cases could have been achieved by including all CFTR2‐causing mutations in the Israeli panel.

Conclusions

Our data reveal an overwhelming hidden abundance of CFTR gene mutations suggesting that expanded preconception carrier screening might achieve higher preconception detection rates.

A Case of Cryptorchidism with Ipsilateral Congenital Unilateral Absence of the Vas Deferens and Contralateral Renal Agenesis

Introduction and Aims. Congenital absence of the vas deferens is an uncommon anomaly and this clinical condition is responsible for up to 1-2% of male infertility. It can be either unilateral or bilateral and the associated anomalies include cryptorchidism, seminal vesicles and ejaculatory ducts anomalies, and renal anomalies such as renal agenesis. We hereby present a case of congenital unilateral absence of vas deferens, which was found incidentally during an evaluation of undescended testis in a patient with ipsilateral renal agenesis. Case Presentation. A 10-month-old boy was referred to the urology clinic with an undescended right testis. Preoperative abdominal ultrasonography showed agenesis of the right kidney and the absence of right vas deferens and epididymis was confirmed during laparoscopic orchiectomy performed due to short right spermatic cord. There were no other concomitant anomalies of the genitourinary system observed in evaluation. Conclusion. Congenital unilateral absence of the vas deferens with cryptorchidism and renal agenesis is a rare diagnostic entity. Cryptorchidism or absent vas deferens found incidentally should lead the physician to evaluate the status of the contralateral vas deferens and conduct a renal tract ultrasound study.

NGS-Based Assay for the Identification of Individuals Carrying Recessive Genetic Mutations in Reproductive Medicine

Next-generation sequencing (NGS) has the capacity of carrier screening in gamete donation (GD) programs. We have developed and validated an NGS carrier-screening test (qCarrier test) that includes 200 genes associated with 368 disorders (277 autosomal recessive and 37 X-linked). Carrier screening is performed on oocyte donation candidates and the male partner of oocyte recipient. Carriers of X-linked conditions are excluded from the GD program, whereas donors are chosen who do not carry mutations for the same gene/disease as the recipients. The validation phase showed a high sensitivity (>99% sensitivity) detecting all single-nucleotide variants, 13 indels, and 25 copy-number variants included in the validation set. A total of 1,301 individuals were analysed with the qCarrier test, including 483 candidate oocyte donors and 635 receptor couples, 105 females receiving sperm donation, and 39 couples seeking pregnancy. We identified 56% of individuals who are carriers for at least one genetic condition and 1.7% of female donors who were excluded from the program due to a carrier state of X-linked conditions. Globally, 3% of a priori assigned donations had a high reproductive risk that could be minimized after testing. Genetic counselling at different stages is essential for helping to facilitate a successful and healthy pregnancy.

Diagnostic Testing in Cystic Fibrosis

Cystic Fibrosis (CF) is a rare, multisystem disease leading to significant morbidity and mortality. CF is caused by defects in the cystic fibrosis transmembrane conductance regulator protein (CFTR), a chloride and bicarbonate transporter. Early diagnosis and access to therapies provides benefits in nutrition, pulmonary health, and cognitive ability. Several screening and diagnostic tests are available to support a diagnosis. We discuss the characteristics of screening and diagnostic tests for CF and guideline-based algorithms using these tools to establish a diagnosis. We discuss classification and management of common "diagnostic dilemmas," including the CFTR-related metabolic syndrome and other CFTR-associated diseases.

Novel mutations and polymorphisms in the CFTR gene associated with three subtypes of congenital absence of vas deferens

OBJECTIVE

To study the new genotypes in congenital absence of vas deferens (CAVD) and the correlation with different phenotypes, and to investigate the pathogenesis of the disease based on bioinformatics analysis.

DESIGN

Case-control study.

SETTING

University-affiliated tertiary teaching hospital.

PATIENT(S)

Nineteen patients with CAVD and azoospermia. The time period of the study was from May 2013 to April 2014.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sanger sequencing was performed in the coding regions and intron-exon boundaries of the cystic fibrosis transmembrane regulator CFTR gene on the polymerase chain reaction (PCR) products. Mutations/variations were identified and compared with the control subjects, and bioinformatics analysis searched in the dbSNP and 1000 Genomes Project. Functional effects of the novel mutations were predicted. Structural modeling of the wild and mutant proteins was also performed.

RESULT(S)

A total of 8 mutations were identified in 12 patients, 4 of which were novel (c.4433C>G, c.3469-3C>A, c.1357delT, and c.3407C>T). The mutation c.4433C>G occurred in the PSD-95/DLG/ZO-1 (PDZ)-binding motif in the CFTR protein, which was predicted to disrupt the interaction between CFTR and CFTR-associated ligand (CAL). Another missense mutation, c.3407C>T, was predicted to damage and destroy the transmembrane adenosine triphosphate (ATP)-binding cassette domain. The splicing mutation, c.3469-3C>A, was predicted to truncate exon 22 by Human Splicing Finder. The frameshift mutation, c.1357delT, was predicted to introduce a premature stop codon at position 453 and lead to 1,012 amino acids truncation at the carboxyl terminus of the CFTR protein.

CONCLUSION(S)

This study illustrates the significance of whole exon sequencing of the CFTR gene in patients with CAVD. It is essential for determining the pathogenesis of novel mutations using bioinformatics analysis and to identify correlation between new genotypes and phenotypes.

Genetic and electrophysiological characteristics of recurrent acute pancreatitis

OBJECTIVES

The aim was to present the workup of patients with acute recurrent pancreatitis (ARP) for genetic analysis and electrophysiological testing.

METHODS

Patients with ARP with unknown etiology were referred for genetic testing and evaluation of cystic fibrosis transmembrane conductor regulator (CFTR) function by nasal potential difference (NPD) testing.

RESULTS

A total of 67 patients were evaluated. The mean age was 23 ± 17 years (median 17.0 years, range 1.5-72 years); 90% were Jewish and 10% Arab. Ten (15%) patients carried PRSS1 gene mutation (K23R(7), R122H(2), and D21A(1)). One patient had K172E/- (chymotrypsin C [CTRC]) mutation, 1 had I42M (serine protease inhibitor Kazal type 1 [SPINK1])/V235I (CTRC) together with ΔF508/5T, 1 patient had R67H (SPINK1)/V235I (CTRC), and 1 patient had V235I (CTRC)/-. Ten of 67 (15%) patients submitted for CFTR gene testing carried mutations (ΔF508/L997F, ΔF508/5T(11TG), W1282/5T(12TG), W1282X/Y1014C, ΔF508/R31C, R117H/-, R117H/Y1014C, D1152H/-, 5T(11TG)/-, and L997F/-). Fifty-four (80%) patients underwent sweat testing. Of these, 5 had sweat chloride ≥60 mEq/L, and 22 patients had sweat chloride from 40 to 60 mEq/L. Of the 56 (83%) patients had nasal potential difference testing, 4 (6%) with abnormal results.

CONCLUSIONS

One-third (34%) of patients with ARP carry mutations for hereditary pancreatitis including rare mutations (K23R), and 12.5% have evidence of cftr mutations and 10% had CFTR dysfunction underscoring the importance of genetic and functional workup of these patients.

Congenital bilateral absence of the vas deferens: the impact of spermatogenesis quality on intracytoplasmic sperm injection outcomes in 108 men

In azoospermic men with congenital bilateral absence of the vas deferens (CBAVD), it is not known whether the outcomes of intracytoplasmic sperm injection (ICSI) depend on the quality of testicular spermatogenesis (as determined histopathologically). We retrospectively studied the impact of spermatogenesis quality on ICSI outcomes in 108 azoospermic men with CBAVD consulting in a university hospital's department of andrology and reproductive biology. As part of an ICSI program, sperm samples were obtained from the epididymis [by microsurgical epididymal sperm aspiration (MESA); n = 47] or the testis [by testicular sperm extraction (TESE); n = 14] or both (MESA + TESE, n = 47). In the TESE group (i.e., TESE-only and MESA + TESE), spermatogenesis was normal in 21 of the 108 men (19.4%) and hypospermatogenesis occurred in 33 (30.5%). The fertilization rate was significantly lower in the hypospermatogenic group than in the normospermatogenesis group (65.6 and 72.9%, respectively; p = 0.02); this was also true for the embryo cleavage rate (88.6 and 92.1%, respectively; p = 0.007), and the proportion of embryos with fewer than 30% of enucleate fragments (79.5 and 86.9%, respectively; p = 0.02). Our study results showed that impaired spermatogenesis had a negative impact on certain early-stage biological outcomes of ICSI. In CBAVD, male factors are likely to exert a harmful effect on the early stages of embryo development.

SNaPshot assay for the detection of the most common CFTR mutations in infertile men

Congenital bilateral absence of vas deferens (CBAVD) is the most common CFTR-related disorder (CFTR-RD) that explains about 1-2% of the male infertility cases. Controversial data have been published regarding the involvement of CFTR mutations in infertile men with non-obstructive azoospermia and oligozoospermia. Here, we describe single base extension (SNaPshot) assay for detection of 11 common CFTR mutations: F508del, G542X, N1303K, 621+1G->T, G551D, R553X, R1162X, W1282X, R117H, 2184insA and 1717-1G->A and IVS8polyT variants. The assay was validated on 50 previously genotyped samples and was used to screen a total of 369 infertile men with different impairment of spermatogenesis and 136 fertile controls. Our results show that double heterozygosity of cystic fibrosis (CF) and CFTR-related disorder (CFTR-RD) mutations are found in a high percentage (22.7%) of infertile men with obstructive azoospermia, but not in other studied groups of infertile men. The SNaPshot assay described here is an inexpensive, fast and robust method for primary screening of the most common CFTR mutations both in patients with classical CF and CFTR-RD. It can contribute to better understanding of the role of CFTR mutations in impaired spermatogenesis, ultimately leading to improved management of infertile men.

Heterogeneous spectrum of mutations in CFTR gene from Indian patients with congenital absence of the vas deferens and their association with cystic fibrosis genetic modifiers

Cystic fibrosis (CF) is usually considered a rare disease in the Indian population. Two studies have reported on the frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in Indian males with congenital absence of the vas deferens (CAVD), however, data on the spectrum of CFTR gene mutations are still lacking. Therefore, the present study was designed to identify the spectrum of CFTR gene mutations as well as to investigate an association of CF genetic modifiers in the penetrance of CAVD in infertile Indian men. A total of 60 consecutive infertile males with a diagnosis of CAVD were subjected to CFTR gene analysis which revealed 13 different CFTR gene mutations and 1 intronic variant that led to aberrant splicing. p.Phe508del (n = 16) and p.Arg117His (n = 4) were among the most common severe forms of CFTR mutations identified. The IVS8-T5 allele, which is considered as a mild form of CFTR mutation, was found with an allelic frequency of 28.3%. Eight novel mutations were also identified in the CFTR gene from our patient cohort. It is noteworthy that the spectrum of CFTR gene mutation is heterogeneous, with exon 4 and exon 11 as hot spot regions. Moreover, we also found an association of the CF genetic modifiers, viz., transforming growth factor (TGF)-β1 and endothelial receptor type-A (EDNRA) genes with the CAVD phenotype. The findings are of considerable clinical significance because men suffering from infertility due to CAVD can decide to use artificial reproduction technology. The children of men with CAVD are at risk of carrying CFTR mutations; therefore, genetic counseling is a crucial step for such patients. With special reference to developing countries, such as India, where whole gene sequencing is not feasible, the outcome of our study will make the screening procedure for CFTR gene simpler and more cost-effective as we have identified hot spot regions of the CFTR gene which are more prone to mutation in Indian males with CAVD. Moreover, this is the first study from the Indian population to investigate the association of CF genetic modifiers with penetrance of the CAVD phenotype. The observed association of the genetic modifiers TGF-β1 and EDNRA in the penetrance of CAVD further supports their involvement in genesis of the vas deferens.

A case of congenital unilateral absence of the vas deferens

Background

Congenital unilateral absence of the vas deferens occurs in 0.5%–1.0% of males. It has been associated with various genitourinary abnormalities, including renal agenesis. We report a case of congenital unilateral absence of the vas deferens found incidentally during vasectomy in a patient with known unilateral renal agenesis.

Case presentation

A 24-year-old male presented to our urology clinic requesting vasectomy. His past history was significant for left renal agenesis. Following successful right vasectomy, several attempts to locate the left vas deferens were unsuccessful. We diagnosed congenital unilateral absence of the vas deferens. Follow-up semen analysis showed azoospermia.

Conclusion

As vasectomies are increasingly performed in outpatient settings, it is imperative that physicians be aware of this condition, which can be recognized by a simple physical exam. Recognition could prevent unnecessary surgery and prompt providers to investigate for associated abnormalities.

Next generation diagnostics of cystic fibrosis and CFTR-related disorders by targeted multiplex high-coverage resequencing of CFTR

BACKGROUND

Here we have developed a novel and much more efficient strategy for the complete molecular characterisation of the cystic fibrosis (CF) transmembrane regulator (CFTR) gene, based on multiplexed targeted resequencing. We have tested this approach in a cohort of 92 samples with previously characterised CFTR mutations and polymorphisms.

METHODS

After enrichment of the pooled barcoded DNA libraries with a custom NimbleGen SeqCap EZ Choice array (Roche) and sequencing with a HiSeq2000 (Illumina) sequencer, we applied several bioinformatics tools to call mutations and polymorphisms in CFTR.

RESULTS

The combination of several bioinformatics tools allowed us to detect all known pathogenic variants (point mutations, short insertions/deletions, and large genomic rearrangements) and polymorphisms (including the poly-T and poly-thymidine-guanine polymorphic tracts) in the 92 samples. In addition, we report the precise characterisation of the breakpoints of seven genomic rearrangements in CFTR, including those of a novel deletion of exon 22 and a complex 85 kb inversion which includes two large deletions affecting exons 4-8 and 12-21, respectively.

CONCLUSIONS

This work is a proof-of-principle that targeted resequencing is an accurate and cost-effective approach for the genetic testing of CF and CFTR-related disorders (ie, male infertility) amenable to the routine clinical practice, and ready to substitute classical molecular methods in medical genetics.

A comprehensive review of genetics and genetic testing in azoospermia

Azoospermia due to obstructive and non-obstructive mechanisms is a common manifestation of male infertility accounting for 10-15% of such cases. Known genetic factors are responsible for approximately 1/3 of cases of azoospermia. Nonetheless, at least 40% of cases are currently categorized as idiopathic and may be linked to unknown genetic abnormalities. It is recommended that various genetic screening tests are performed in azoospermic men, given that their results may play vital role in not only identifying the etiology but also in preventing the iatrogenic transmission of genetic defects to offspring via advanced assisted conception techniques. In the present review, we examine the current genetic information associated with azoospermia based on results from search engines, such as PUBMED, OVID, SCIENCE DIRECT and SCOPUS. We also present a critical appraisal of use of genetic testing in this subset of infertile patients.

Management of male infertility due to congenital bilateral absence of vas deferens should not ignore the diagnosis of cystic fibrosis

Microsurgical or percutaneous epididymal sperm aspiration and intracytoplasmic sperm injection (ICSI) are proposed to overcome male infertility due to congenital bilateral absence of vas deferens (CBAVD). CBAVD has been associated with mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and consequently, genetic counselling has to be addressed before beginning ICSI procedure. However, management of male infertility due to CBAVD should not ignore a mild form of cystic fibrosis. We describe the case of cystic fibrosis late diagnosis performed in a 49-year-old infertile men with CBAVD. CFTR molecular testing detected two mutations F508del and A455E corresponding to a cystic fibrosis genotype. Pneumological evaluation revealed a severe obstructive respiratory disease, bronchiectasis and high sweat chloride levels. Symptoms consistent with a cystic fibrosis have to be identified in infertile men with CBAVD before beginning assisted reproductive procedures.

Significance of CFTR gene mutations in patients with congenital aplasia of vas deferens with special regard to renal aplasia

Between 1994 and 2010, a total of 123 patients with obstructive azoospermia due to aplasia of vas deferens (CAVD) were surgically treated. In 110 patients, the condition was bilateral (CBAVD), 13 men had unilateral aplasia (CUAVD), and 10 patients additionally had aplasia of one kidney. All patients underwent CFTR genetic testing, which detected two mutations (homozygous or compound heterozygous condition) in 38%, one mutation in 34% and no mutation in 28% of the patients with CBAVD. Neither the azoospermic patients with congenital unilateral aplasia of vas deferens nor those with CBAVD and renal aplasia were found to have CFTR mutations. The results militate against the assumption that there is an association between the CFTR gene and unilateral aplasia of vas deferens or bilateral aplasia of vas deferens with renal involvement.

Disrupted post-transcriptional regulation of the cystic fibrosis transmembrane conductance regulator (CFTR) by a 5'UTR mutation is associated with a CFTR-related disease

Cystic fibrosis (CF) is characterized as a single-gene disorder with a simple, autosomal recessive mode of inheritance. However, translation of cystic fibrosis transmembrane conductance regulator (CFTR) genotype into CF phenotype is influenced by nucleotide sequence variations at multiple genetic loci, and individuals heterozygous for CFTR mutations are predisposed to a range of CFTR-related conditions, such as disseminated bronchiectasis. CF disease severity and CFTR-related conditions are more akin to complex, multifactorial traits, which are increasingly being associated with mutations that perturb gene expression. We have identified a patient with disseminated bronchiectasis, who is heterozygous for a single-nucleotide substitution in the CFTR 5' untranslated region (UTR) (c.-34C>T). The c.-34C>T mutation creates an upstream AUG codon and upstream open reading frame that overlaps, and is out of frame with, the CFTR protein coding sequence. Using luciferase reporter constructs, we have shown that the c.-34C>T mutation decreases gene expression by 85-99%, by reducing translation efficiency and mRNA stability. This is the first CFTR regulatory mutation shown to act at a posttranscriptional level that reduces the synthesis of normal CFTR (Class V), and reaffirms the importance of regulatory mutations as a genetic basis of multifactorial phenotypes.

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

PURPOSE

To evaluate five common cystic fibrosis trans-membrane conductance regulator (CFTR) mutations (ΔF508, G542X, R117H, W1282X and N1303K) in the Iranian infertile men with noncongenital absence of vas deferens (CAVD) obstructive azoospermia.

METHODS

The common CFTR gene mutations were tested on blood samples from 53 infertile men with non-CAVD obstructive azoospermia and 50 normal men as control individuals. Genomic DNA is extracted from the whole blood and the common CFTR mutations have been detected by the amplification refractory mutation system (ARMS) techniques.

RESULTS

The common CFTR mutations were found positive in 5/53)9.43%(for ΔF508 and 4/53)7.55%(for G542X mutation of all patients tested. Also, no CFTR mutations were detected in the normal men.

CONCLUSION

The common CFTR mutations were detected in 9/53(17%) infertile men with non-CAVD obstructive azoospermia. Pre-treatment CFTR mutation analysis remains critical to distinguish cystic fibrosis (CF) genotypes for men with non CAVD obstructive azoospermia.

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.

Screening of ΔF508 mutation and IVS8-poly T polymorphism in CFTR gene in Tunisian infertile men without CBAVD

It is well established that cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations are involved in congenital bilateral absence of the vas deferens (CBAVD), causing obstructive azoospermia and male infertility. Also, several studies reported a relatively high prevalence of CFTR gene mutations in healthy men presenting reduced sperm quality. In this study, we investigate ΔF508 mutation and IVS8-polyT polymorphism in CFTR gene in Tunisian infertile men without CBAVD. Genetic analyses were performed in 148 infertile patients and 126 fertile individuals. The polymorphic IVS8-polyT tract in CFTR gene was analysed in only 129 infertile patients and 54 individuals of control group. As well, we screened for Y chromosome microdeletions in all infertile patients. No ΔF508 mutation was diagnosed either in infertile patients or in control group. 5T allele of IVS8-polyT tract was found in both infertile men (4.26%) and fertile individuals (8.33%). 5T/5T genotype was observed only in two azoospermic patients without Y microdeletions. The most frequent genotype of IVS8-polyT tract in infertile men and controls was 7T/7T (69.75% and 59.25% respectively). There was no association between IVS8-polyT polymorphism and reduced semen quality. Neither ΔF508 mutation nor 5T allele is involved in pathogenesis of male infertility in Tunisian infertile patients without CBAVD.