Enhanced frequency of CFTR gene variants in couples who are candidates for assisted reproductive technology treatment

Russian Regional Differences in Allele Frequencies of CFTR Gene Variants: Genetic Monitoring of Infertile Couples

A male factor, commonly associated with poor semen quality, is revealed in about 50% of infertile couples. CFTR gene (Cystic Fibrosis Transmembrane Conduction Regulator) variants are one of the common genetic causes of azoospermia-related male infertility. Notably, the spectrum and frequency of pathogenic CFTR variants vary between populations and geographical regions. In this work, we made an attempt to evaluate the allele frequency (AF) of 12 common CFTR variants in infertile Russian men and healthy individuals from different districts of Russia. Because of the limited number of population-based studies on Russian individuals, we characterized the population AFs based on data from the Registry of Russian cystic fibrosis (CF) patients. In addition to the CF patient registry, we estimated the local frequencies of the same set of variants based on the results of genotyping of CF patients in local biocollections (from St. Petersburg and Yugra regions). AFs of common CFTR variants calculated based on registry and biocollection data showed good concordance with directly measured population AFs. The estimated region-specific frequencies of CFTR variants allowed us to uncover statistically significant regional differences in the frequencies of the F508del (c.1521_1523del; p.Phe508del) and CFTRdele2,3(21kb) (c.54-5940_273+10250del21kb; p.Ser18ArgfsX) variants. The data from population-based studies confirmed previous observations that F508del, CFTRdele2,3(21kb), and L138ins (c.413_415dup; p.Leu138dup)variants are the most abundant among infertile patients, and their frequencies are significantly lower in healthy individuals and should be taken into account during genetic monitoring of the reproductive health of Russian individuals.

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.

One4Two®: An Integrated Molecular Approach to Optimize Infertile Couples' Journey

The current diagnostic path of infertile couples is long lasting and often ineffective. Genetic tests, in particular, appear as a limiting step due to their jeopardized use on one side, and to the limited number of genes evaluated on the other. In this context, the development and diffusion, also in routine diagnostic settings, of next generation sequencing (NGS)-based methods for the analyses of several genes in multiple subjects at a time is improving the diagnostic sensitivity of molecular analyses. Thus, we developed One4Two^®, a custom NGS panel to optimize the diagnostic journey of infertile couples. The panel validation was carried out in three steps analyzing a total of 83 subjects. Interestingly, all the previously identified variants were confirmed, assessing the analytic sensitivity of the method. Moreover, additional pathogenic variants have been identified underlying the diagnostic efficacy of the proposed method. One4Two^® allows the simultaneous analysis of infertility-related genes, disease-genes of common inherited diseases, and of polymorphisms related to therapy outcome. Thus, One4Two^® is able to improve the diagnostic journey of infertile couples by simplifying the whole process not only for patients, but also for laboratories and reproduction specialists moving toward an even more personalized medicine.

Male reproductive health in cystic fibrosis

The impact of cystic fibrosis (CF) on male reproductive health is profound. The vast majority of men with CF are infertile due to obstructive azoospermia. Multiple factors associated with CF contribute to an increased prevalence of testosterone deficiency, which adversely affects muscle mass, bone density, and quality of life. This article reviews the pathophysiology, diagnosis, and management of infertility and testosterone deficiency that occur in men with CF. With improving survival of CF patients, these topics are becoming more significant in their clinical care.

Cystic fibrosis gene mutations and polymorphisms in Saudi men with infertility

BACKGROUND

Some mutations of the cystic fibrosis transmembrane regulator (CFTR) gene may impair spermatogenesis or cause a congenital absence of the vas deferens that manifests as isolated male infertility.

OBJECTIVE

Assess the frequency and analyze the spectrum of CFTR gene variations in Saudi men with primary infertility.

DESIGN

Prospective, cross-sectional.

SETTING

Tertiary care specialist hospital in Jeddah.

PATIENTS AND METHODS

Genomic DNA was extracted from peripheral blood samples of Saudi men who presented with primary infertility to the outpatient andrology clinic with either azoospermia or oligoasthenoteratozoospermia. Polymerase chain reaction and direct sequencing were used to identify all variants of the CFTR gene.

MAIN OUTCOME MEASURES

Proportion of the patients with a mutant CFTR gene and the spectrum of CFTR gene variations.

SAMPLE SIZE

50 infertile Saudi men.

RESULTS

This study identified 10 CFTR gene variants in 7 (14%) subjects (100 chromosomes). The detected variants and polymorphisms were: c.1408G>A, c.4389G>A, c.2562T>G, c.869+11C>T, c.2909-92G>A, c.3469-65C>A, c.1210-6delT, c.1210-6T>A, c.2988+1G>A, and c.1210-13GT>TG.

CONCLUSION

We demonstrated that 14% of the study subjects had one or more CFTR mutations and these were compounded in most of the affected patients. The spectrum of CFTR gene mutations in these subjects was similar to the mutations reported in other studies throughout the world.

LIMITATIONS

Small sample size and the lack of a control group.

CONFLICTS OF INTEREST

None.

Human sperm ion channel (dys)function: implications for fertilization

BACKGROUND

Intensive research on sperm ion channels has identified members of several ion channel families in both mouse and human sperm. Gene knock-out studies have unequivocally demonstrated the importance of the calcium and potassium conductances in sperm for fertility. In both species, the calcium current is carried by the highly complex cation channel of sperm (CatSper). In mouse sperm, the potassium current has been conclusively shown to be carried by a channel consisting of the pore forming subunit SLO3 and auxiliary subunit leucine-rich repeat-containing 52 (LRRC52). However, in human sperm it is controversial whether the pore forming subunit of the channel is composed of SLO3 and/or SLO1. Deciphering the role of the proton-specific Hv1 channel is more challenging as it is only expressed in human sperm. However, definitive evidence for a role in, and importance for, human fertility can only be determined through studies using clinical samples.

OBJECTIVE AND RATIONALE

This review aims to provide insight into the role of sperm ion channels in human fertilization as evidenced from recent studies of sperm from infertile men. We also summarize the key discoveries from mouse ion channel knock-out models and contrast the properties of mouse and human CatSper and potassium currents. We detail the evidence for, and consequences of, defective ion channels in human sperm and discuss hypotheses to explain how defects arise and why affected sperm have impaired fertilization potential.

SEARCH METHODS

Relevant studies were identified using PubMed and were limited to ion channels that have been characterized in mouse and human sperm. Additional notable examples from other species are included as appropriate.

OUTCOMES

There are now well-documented fundamental differences between the properties of CatSper and potassium channel currents in mouse and human sperm. However, in both species, sperm lacking either channel cannot fertilize in vivo and CatSper-null sperm also fail to fertilize at IVF. Sperm-lacking potassium currents are capable of fertilizing at IVF, albeit at a much lower rate. However, additional complex and heterogeneous ion channel dysfunction has been reported in sperm from infertile men, the causes of which are unknown. Similarly, the nature of the functional impairment of affected patient sperm remains elusive. There are no reports of studies of Hv1 in human sperm from infertile men.

WIDER IMPLICATIONS

Recent studies using sperm from infertile men have given new insight and critical evidence supporting the supposition that calcium and potassium conductances are essential for human fertility. However, it should be highlighted that many fundamental questions remain regarding the nature of molecular and functional defects in sperm with dysfunctional ion channels. The development and application of advanced technologies remains a necessity to progress basic and clinical research in this area, with the aim of providing effective screening methodologies to identify and develop treatments for affected men in order to help prevent failed ART cycles. Conversely, development of drugs that block calcium and/or potassium conductances in sperm is a plausible strategy for producing sperm-specific contraceptives.

The evolving role of genetic tests in reproductive medicine

Infertility is considered a major public health issue, and approximately 1 out of 6 people worldwide suffer from infertility during their reproductive lifespans. Thanks to technological advances, genetic tests are becoming increasingly relevant in reproductive medicine. More genetic tests are required to identify the cause of male and/or female infertility, identify carriers of inherited diseases and plan antenatal testing. Furthermore, genetic tests provide direction toward the most appropriate assisted reproductive techniques. Nevertheless, the use of molecular analysis in this field is still fragmented and cumbersome. The aim of this review is to highlight the conditions in which a genetic evaluation (counselling and testing) plays a role in improving the reproductive outcomes of infertile couples. We conducted a review of the literature, and starting from the observation of specific signs and symptoms, we describe the available molecular tests. To conceive a child, both partners' reproductive systems need to function in a precisely choreographed manner. Hence to treat infertility, it is key to assess both partners. Our results highlight the increasing importance of molecular testing in reproductive medicine.

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.

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.

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.

Genotype-phenotype correlation and functional studies in patients with cystic fibrosis bearing CFTR complex alleles

BACKGROUND

The effect of complex alleles in cystic fibrosis (CF) is poorly defined for the lack of functional studies.

OBJECTIVES

To describe the genotype-phenotype correlation and the results of either in vitro and ex vivo studies performed on nasal epithelial cells (NEC) in a cohort of patients with CF carrying cystic fibrosis transmembrane conductance regulator (CFTR) complex alleles.

METHODS

We studied 70 homozygous, compound heterozygous or heterozygous for CFTR mutations: p.[Arg74Trp;Val201Met;Asp1270Asn], n=8; p.[Ile148Thr;Ile1023_Val1024del], n=5; p.[Arg117Leu;Leu997Phe], n=6; c.[1210-34TG[12];1210-12T[5];2930C>T], n=3; p.[Arg74Trp;Asp1270Asn], n=4; p.Asp1270Asn, n=2; p.Ile148Thr, n=6; p.Leu997Phe, n=36. In 39 patients, we analysed the CFTR gating activity on NEC in comparison with patients with CF (n=8) and carriers (n=4). Finally, we analysed in vitro the p.[Arg74Trp;Val201Met;Asp1270Asn] complex allele.

RESULTS

The p.[Ile148Thr;Ile1023_Val1024del] caused severe CF in five compound heterozygous with a class I-II mutation. Their CFTR activity on NEC was comparable with patients with two class I-II mutations (mean 7.3% vs 6.9%). The p.[Arg74Trp;Asp1270Asn] and the p.Asp1270Asn have scarce functional effects, while p.[Arg74Trp;Val201Met;Asp1270Asn] caused mild CF in four of five subjects carrying a class I-II mutation in trans, or CFTR-related disorders (CFTR-RD) in three having in trans a class IV-V mutation. The p.[Arg74Trp;Val201Met;Asp1270Asn] causes significantly (p<0.001) higher CFTR activity compared with compound heterozygous for class I-II mutations. Furthermore, five of six compounds heterozygous with the p.[Arg117Leu;Leu997Phe] had mild CF, whereas the p.Leu997Phe, in trans with a class I-II CFTR mutation, caused CFTR-RD or a healthy status (CFTR activity: 21.3-36.9%). Finally, compounds heterozygous for the c.[1210-34TG[12];1210-12T[5];2930C>T] and a class I-II mutation had mild CF or CFTR-RD (gating activity: 18.5-19.0%).

CONCLUSIONS

The effect of complex alleles partially depends on the mutation in trans. Although larger studies are necessary, the CFTR activity on NEC is a rapid contributory tool to classify patients with CFTR dysfunction.

CFTR Deletion in Mouse Testis Induces VDAC1 Mediated Inflammatory Pathway Critical for Spermatogenesis

Cystic fibrosis is the most common genetic disease among Caucasians and affects tissues including lung, pancreas and reproductive tracts. It has been shown that Endoplasmic Reticulum (ER) stress and heat shock response are two major deregulated functional modules related to CFTR dysfunction. To identify the impact of CFTR deletion during spermatogenesis, we examined the expression of spermiogenesis-related genes in the testis of CFTR mutant mice (CF mice). We confirmed expression changes of MSY2, a germ cell specific RNA binding protein, resulting from deletion of CFTR in testis. Furthermore, real time PCR and Western blot results showed that an inflammatory response was activated in CF mice testis, as reflected by the altered expression of cytokines. We demonstrate for the first time that expression of MSY2 is decreased in CF mice. Our results suggest that CFTR deletion in testis influences inflammatory responses and these features are likely to be due to the unique environment of the seminiferous tubule during the spermatogenesis process. The current study also suggests avenues to understand the pathophysiology of CFTR during spermatogenesis and provides targets for the possible treatment of CFTR-related infertility.

A rigorous approach for selection of optimal variant sets for carrier screening with demonstration of clinical utility

Carrier screening for certain diseases is recommended by major medical and Ashkenazi Jewish (AJ) societies. Most carrier screening panels test only for common, ethnic-specific variants. However, with formerly isolated ethnic groups becoming increasingly intermixed, this approach is becoming inadequate. Our objective was to develop a rigorous process to curate all variants, for relevant genes, into a database and then apply stringent clinical validity classification criteria to each in order to retain only those with clear evidence for pathogenicity. The resulting variant set, in conjunction with next-generation DNA sequencing (NGS), then affords the capability for an ethnically diverse, comprehensive, highly specific carrier-screening assay. The clinical utility of our approach was demonstrated by screening a pan-ethnic population of 22,864 individuals for Bloom syndrome carrier status using a BLM variant panel comprised of 50 pathogenic variants. In addition to carriers of the common AJ founder variant, we identified 57 carriers of other pathogenic BLM variants. All variants reported had previously been curated and their clinical validity documented, or were of a type that met our stringent, preassigned validity criteria. Thus, it was possible to confidently report an increased number of Bloom’s syndrome carriers compared to traditional, ethnicity-based screening, while not reducing the specificity of the screening due to reporting variants of unknown clinical significance.

Prenatal diagnosis of cystic fibrosis: an experience of 181 cases

BACKGROUND

The demand for prenatal diagnosis (PD) of cystic fibrosis (CF) is increasing.

METHODS

We performed pre-test multidisciplinary counselling for 192 couples at CF reproductive risk. In 11/192 (5.7%) cases PD was not performed mainly because counselling revealed a reproductive risk for atypical (mild) CF, while 181 PDs were performed in couples revealed at high risk for CF mainly because they already had a CF child (148/181, 81.8%) or had been identified through cascade screening (28/181, 15.5%).

RESULTS

In 167/181 (92.3%) cases (including two dichorionic twin pregnancies), PD was performed on chorionic villi, and in 14 on amniocyte DNA. Only 1/181 PD was unsuccessful. In all other cases, single tandem repeat analysis excluded maternal contamination, and PD was made within 7 days of sampling. In total 116/180 (64.4%) PDs were made with dot-blot analysis; 40 (22.2%) required gene sequencing; in 4/180 cases we tested the gene for large rearrangements; in 23/180 (12.8%) cases linkage analysis was necessary because parental mutation(s) were unknown. Forty-two out of 180 (23.3%) PDs revealed an affected foetus. All couples but one interrupted pregnancy. The first twin PD revealed the absence (1 foetus) and the presence of one mutation (the other foetus); the second twin PD revealed one parental mutation (1 foetus) and both parental mutations (the other foetus); the couple planned selective interruption.

CONCLUSIONS

PD for CF should be performed in reference laboratories equipped for gene scanning and linkage analysis, with a multidisciplinary staff able to offer counselling to couples during all phases of PD.

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.

The CFTR M470V, intron 8 poly-T, and 8 TG-repeats detection in Chinese males with congenital bilateral absence of the vas deferens

Purpose. To evaluate the significance of molecular detection of cystic fibrosis transmembrane conductance regulator (CFTR) M470V, intron 8 poly-T, and intron 8 TG-repeats in congenital bilateral absence of the vas deferens (CBAVD). Methods. Eighty-nine male patients with CBAVD and 103 healthy males were included in this study. Polymerase chain reaction was performed to amplify the polymorphic regions using primers from conserved regions. M470V was genotyped using real-time PCR by cycling probe. The exon 9 DNA sequence was determined using an automated sequencer. TG-repeats and poly-T were identified by direct sequencing analysis. Results. The 5T allele distribution was 0.32, 0.66 for 7T, and 0.02 for 9T in CBAVD males, respectively. In contrast, the 5T allele distribution was 0.03, 0.96 for 7T, and 0.01 for 9T in healthy control. Study of the polymorphisms of the upstream of exon 9 revealed a higher frequency of 5T allele in the CBAVD males. All cases with TG13T5 haplotype and TG12T5 homozygous led to CBAVD. The CFTR TG12T5-V470 variant haplotype was associated with CBAVD. Conclusion. The 5T allele of intron 8 of CFTR has clinically significant association with CBAVD. TG13T5 and TG12T5 homozygously led to CBAVD, and TG12T5-V470 may also lead to CBAVD.

A new method to improve the clinical evaluation of cystic fibrosis patients by mucus viscoelastic properties

In cystic fibrosis (CF) patients airways mucus shows an increased viscoelasticity due to the concentration of high molecular weight components. Such mucus thickening eventually leads to bacterial overgrowth and prevents mucus clearance. The altered rheological behavior of mucus results in chronic lung infection and inflammation, which causes most of the cases of morbidity and mortality, although the cystic fibrosis complications affect other organs as well. Here, we present a quantitative study on the correlation between cystic fibrosis mucus viscoelasticity and patients clinical status. In particular, a new diagnostic parameter based on the correlation between CF sputum viscoelastic properties and the severity of the disease, expressed in terms of FEV1 and bacterial colonization, was developed. By using principal component analysis, we show that the types of colonization and FEV1 classes are significantly correlated to the elastic modulus, and that the latter can be used for CF severity classification with a high predictive efficiency (88%). The data presented here show that the elastic modulus of airways mucus, given the high predictive efficiency, could be used as a new clinical parameter in the prognostic evaluation of cystic fibrosis.

Changes in transcriptome of native nasal epithelium expressing F508del-CFTR and intersecting data from comparable studies

Background

Microarray studies related to cystic fibrosis (CF) airway gene expression have gone some way in clarifying the complex molecular background of CF lung diseases, but have made little progress in defining a robust “molecular signature” associated with mutant CFTR expression. Disparate methodological and statistical analyses complicate comparisons between independent studies of the CF transcriptome, and although each study may be valid in isolation, the conclusions reached differ widely.

Methods

We carried out a small-scale whole genome microarray study of gene expression in human native nasal epithelial cells from F508del-CFTR homozygotes in comparison to non-CF controls. We performed superficial comparisons with other microarray datasets in an attempt to identify a subset of regulated genes that could act as a signature of F508del-CFTR expression in native airway tissue samples.

Results

Among the alterations detected in CF, up-regulation of genes involved in cell proliferation, and down-regulation of cilia genes were the most notable. Other changes involved gene expression changes in calcium and membrane pathways, inflammation, defence response, wound healing and the involvement of estrogen signalling. Comparison of our data set with previously published studies allowed us to assess the consistency of independent microarray data sets, and shed light on the limitations of such snapshot studies in measuring a system as subtle and dynamic as the transcriptome. Comparison of in-vivo studies nevertheless yielded a small molecular CF signature worthy of future investigation.

Conclusions

Despite the variability among the independent studies, the current CF transcriptome meta-analysis identified subsets of differentially expressed genes in native airway tissues which provide both interesting clues to CF pathogenesis and a possible CF biomarker.

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.

The susceptibility of T5-TG12 of the CFTR gene in chronic bronchitis occurrence in a Chinese population in Jiangsu province, China

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have been implicated in the onset of cystic fibrosis and other clinical respiratory disorders. In the present study, we investigated the role of CFTR variations, poly-T, TG-repeats, and M470V in susceptibility to bronchial asthma and chronic bronchitis in a Chinese population in Jiangsu province, China. A total of 72 bronchial asthma patients, 68 chronic bronchitis patients, and 117 healthy subjects were included in this study. The Tn-TGm haplotype was sequenced and the CFTR variant M470V was detected using restriction fragment length polymorphism (RFLP). We found that the frequency of T5-TG12-V470 in chronic bronchitis patients was 0.07%, which was notably higher than that in healthy subjects (0.01%) and bronchial asthma patients (0.04%). Thus, the presence of the T5-TG12 haplotype of the CFTR gene is likely to play a role in the development and progression of respiratory conditions, such as chronic bronchitis.