Mutations in the cystic fibrosis gene in patients with congenital absence of the vas deferens

The Role of Pancreatitis Risk Genes in Endocrine Insufficiency Development After Acute Pancreatitis in Children

BACKGROUND & AIMS

Acute pancreatitis (AP) is increasingly recognized as a risk factor for diabetes mellitus (DM). We aimed to study the association of pancreatitis genes with pancreatic endocrine insufficiency (pre-DM and DM) development post-AP in children.

METHODS

This was an observational cohort study that enrolled subjects ≤21 years with their first episode of AP and followed them for 12 months for the development of pancreatic endocrine insufficiency. Pancreatitis risk genes (CASR, CEL, CFTR, CLDN2, CPA1, CTRC, PRSS1, SBDS, SPINK1, and UBR1) were sequenced. A genetic risk score was derived from all genes with univariable P < .15.

RESULTS

A total 120 subjects with AP were genotyped. Sixty-three subjects (52.5%) had at least 1 reportable variant identified. For modeling the development of pancreatic endocrine insufficiency at 1 year, 6 were excluded (2 with DM at baseline, 3 with total pancreatectomy, and 1 death). From this group of 114, 95 remained normoglycemic and 19 (17%) developed endocrine insufficiency (4 DM, 15 pre-DM). Severe AP (58% vs 20%; P = .001) and at least 1 gene affected (79% vs 47%; P = .01) were enriched among the endocrine-insufficient group. Those with versus without endocrine insufficiency were similar in age, sex, race, ethnicity, body mass index, and AP recurrence. A model for pre-DM/DM development included AP severity (odds ratio, 5.17 [1.66-16.15]; P = .005) and genetic risk score (odds ratio, 4.89 [1.83-13.08]; P = .002) and had an area under the curve of 0.74.

CONCLUSIONS

In this cohort of children with AP, pancreatitis risk genes and AP disease severity were associated with pre-DM or DM development post-AP.

Update on advances in cystic fibrosis towards a cure and implications for primary care clinicians

During the past quarter century, the diagnosis and treatment of cystic fibrosis (CF) have been transformed by molecular sciences that initiated a new era with discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The knowledge gained from that breakthrough has had dramatic clinical impact. Although once a diagnostic dilemma with long delays, preventable deaths, and irreversible pathology, CF can now be routinely diagnosed shortly after birth through newborn screening programs. This strategy of pre-symptomatic identification has eliminated the common diagnostic "odyssey" that was a failure of the healthcare delivery system causing psychologically traumatic experiences for parents. Therapeutic advances of many kinds have culminated in CFTR modulator treatment that can reduce the effects of or even correct the molecular defect in the chloride channel -the basic cause of CF. This astonishing advance has transformed CF care as described fully herein. Despite this impressive progress, there are challenges and controversies in the delivery of care. Issues include how best to achieve high sensitivity newborn screening with acceptable specificity; what course of action is appropriate for children who are identified through the unavoidable incidental findings of screening tests (CFSPID/CRMS cases and heterozygote carriers); how best to ensure genetic counseling; when to initiate the very expensive but life-saving CFTR modulator drugs; how to identify new CFTR modulator drugs for patients with non-responsive CFTR variants; how to adjust other therapeutic modalities; and how to best partner with primary care clinicians. Progress always brings new challenges, and this has been evident worldwide for CF. Consequently, this article summarizes the major advances of recent years along with controversies and describes their implications with an international perspective.

Male Factor Infertility: What Every OB/GYN Should Know

Male factor infertility plays a role in approximately 30% of infertility cases. Various causes of male factor infertility exist including congenital, acquired, idiopathic, or environmental factors. Identifying the underlying etiology of male factor infertility is a key step toward providing appropriate counseling, effective treatment options, and improving outcomes for couples with infertility. Although the recent advances and developments in assisted reproductive technology have undoubtedly improved fertility outcomes, clinicians must understand the scope of reproductive urologists in the evaluation and treatment of male infertility to provide comprehensive counseling, appropriate referral, comprehensive evaluation, and correct surgical sperm retrieval techniques when needed.

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.

New statistical selection method for pleiotropic variants associated with both quantitative and qualitative traits

BACKGROUND

Identification of pleiotropic variants associated with multiple phenotypic traits has received increasing attention in genetic association studies. Overlapping genetic associations from multiple traits help to detect weak genetic associations missed by single-trait analyses. Many statistical methods were developed to identify pleiotropic variants with most of them being limited to quantitative traits when pleiotropic effects on both quantitative and qualitative traits have been observed. This is a statistically challenging problem because there does not exist an appropriate multivariate distribution to model both quantitative and qualitative data together. Alternatively, meta-analysis methods can be applied, which basically integrate summary statistics of individual variants associated with either a quantitative or a qualitative trait without accounting for correlations among genetic variants.

RESULTS

We propose a new statistical selection method based on a unified selection score quantifying how a genetic variant, i.e., a pleiotropic variant associates with both quantitative and qualitative traits. In our extensive simulation studies where various types of pleiotropic effects on both quantitative and qualitative traits were considered, we demonstrated that the proposed method outperforms the existing meta-analysis methods in terms of true positive selection. We also applied the proposed method to a peanut dataset with 6 quantitative and 2 qualitative traits, and a cowpea dataset with 2 quantitative and 6 qualitative traits. We were able to detect some potentially pleiotropic variants missed by the existing methods in both analyses.

CONCLUSIONS

The proposed method is able to locate pleiotropic variants associated with both quantitative and qualitative traits. It has been implemented into an R package 'UNISS', which can be downloaded from http://github.com/statpng/uniss.

Nature and nurture: understanding phenotypic variation in inborn errors of immunity

The overall disease burden of pediatric infection is high, with widely varying clinical outcomes including death. Among the most vulnerable children, those with inborn errors of immunity, reduced penetrance and variable expressivity are common but poorly understood. There are several genetic mechanisms that influence phenotypic variation in inborn errors of immunity, as well as a body of knowledge on environmental influences and specific pathogen triggers. Critically, recent advances are illuminating novel nuances for fundamental concepts on disease penetrance, as well as raising new areas of inquiry. The last few decades have seen the identification of almost 500 causes of inborn errors of immunity, as well as major advancements in our ability to characterize somatic events, the microbiome, and genotypes across large populations. The progress has not been linear, and yet, these developments have accumulated into an enhanced ability to diagnose and treat inborn errors of immunity, in some cases with precision therapy. Nonetheless, many questions remain regarding the genetic and environmental contributions to phenotypic variation both within and among families. The purpose of this review is to provide an updated summary of key concepts in genetic and environmental contributions to phenotypic variation within inborn errors of immunity, conceptualized as including dynamic, reciprocal interplay among factors unfolding across the key dimension of time. The associated findings, potential gaps, and implications for research are discussed in turn for each major influencing factor. The substantial challenge ahead will be to organize and integrate information in such a way that accommodates the heterogeneity within inborn errors of immunity to arrive at a more comprehensive and accurate understanding of how the immune system operates in health and disease. And, crucially, to translate this understanding into improved patient care for the millions at risk for serious infection and other immune-related morbidity.

Sexual and Reproductive Health Among Men With Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Due to the distribution of the CFTR protein, CF presents with a heterogeneous phenotype. Men with CF may present with infertility due to congenital abnormalities of the vas deferens. In addition, they may experience testosterone deficiency. Today, they can father biological children with assisted reproductive technologies. We reviewed the current literature on the pathophysiology of these conditions, describe interventions that allow men with CF to conceive biological children, and provide recommendations for management of CF patients with reproductive health concerns.

Prevalence of CFTR variants in primary immunodeficiency patients with bronchiectasis is an important modifying cofactor

BACKGROUND

Cystic fibrosis (CF) is one of the most common life-limiting autosomal-recessive disorders and is caused by genetic defects in the CF transmembrane conductance regulator (CFTR) gene. Some of the features of this multisystem disease can be present in primary immunodeficiency (PID).

OBJECTIVE

We hypothesized that a carrier CFTR status might be associated with worse outcome regarding structural lung disease in patients with PID.

METHODS

A within-cohort and population-level statistical genomic analysis of a large European cohort of PID patients was performed using genome sequence data. Genomic analysis of variant pathogenicity was performed.

RESULTS

Compared to the general population, p.Phe508del carriage was enriched in lung-related PID. Additionally, carriage of several pathogenic CFTR gene variants were increased in PID associated with structural lung damage compared to PID patients without the structural lung damage. We identified 3 additional biallelic cases, including several variants not traditionally considered to cause CF.

CONCLUSION

Genome sequencing identified cases of CFTR dysfunction in PID, driving an increased susceptibility to infection. Large national genomic services provide an opportunity for precision medicine by interpreting subtle features of genomic diversity when treating traditional Mendelian disorders.

A novel ADGRG2 truncating variant associated with X-linked obstructive azoospermia in a large Chinese pedigree

PURPOSE

In this study, we aimed to identify sterility-related variants in a Chinese pedigree with male infertility and to reveal the different phenotypes and intracytoplasmic sperm injection (ICSI) outcomes of the affected members.

METHODS

Physical examinations were performed on male patients. G-band karyotype analysis, copy number variation sequencing, and quantitative fluorescent PCR were conducted to detect common chromosomal disorders in the probands. Whole-exome sequencing and Sanger sequencing were applied to identify the pathogenic genes and the protein expression changes caused by the very mutation were identified by Western Blot in vitro.

RESULTS

A novel nonsense mutation (c.908C > G: p.S303*) in the ADGRG2 was identified in all infertile male patients of the pedigree, which was inherited from their mothers. This variant was absent from the human genome databases. This mutation was also unexpectedly found in a male member with normal reproductive capability. Members with the mutation had different genitalia phenotypes, ranging from normal to dilated phenotypes of the vas deferens, spermatic veins and epididymis. There was a truncated ADGRG2 protein in vitro after mutation. Of the three patients' wives treated with ICSI, only one successfully gave birth.

CONCLUSIONS

Our study is the first to report the c.908C > G: p.S303* mutation in the ADGRG2 in an X-linked azoospermia pedigree and is the first to report normal fertility in a member with this mutation, expanding the mutation spectrum and phenotype spectrum of this gene. In our study, ISCI had a success rate of only one-third in couples including men with azoospermia with this mutation.

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 .

Gene differential co-expression analysis of male infertility patients based on statistical and machine learning methods

Male infertility has always been one of the important factors affecting the infertility of couples of gestational age. The reasons that affect male infertility includes living habits, hereditary factors, etc. Identifying the genetic causes of male infertility can help us understand the biology of male infertility, as well as the diagnosis of genetic testing and the determination of clinical treatment options. While current research has made significant progress in the genes that cause sperm defects in men, genetic studies of sperm content defects are still lacking. This article is based on a dataset of gene expression data on the X chromosome in patients with azoospermia, mild and severe oligospermia. Due to the difference in the degree of disease between patients and the possible difference in genetic causes, common classical clustering methods such as k-means, hierarchical clustering, etc. cannot effectively identify samples (realize simultaneous clustering of samples and features). In this paper, we use machine learning and various statistical methods such as hypergeometric distribution, Gibbs sampling, Fisher test, etc. and genes the interaction network for cluster analysis of gene expression data of male infertility patients has certain advantages compared with existing methods. The cluster results were identified by differential co-expression analysis of gene expression data in male infertility patients, and the model recognition clusters were analyzed by multiple gene enrichment methods, showing different degrees of enrichment in various enzyme activities, cancer, virus-related, ATP and ADP production, and other pathways. At the same time, as this paper is an unsupervised analysis of genetic factors of male infertility patients, we constructed a simulated data set, in which the clustering results have been determined, which can be used to measure the effect of discriminant model recognition. Through comparison, it finds that the proposed model has a better identification effect.

Translational Bioinformatics for Human Reproductive Biology Research: Examples, Opportunities and Challenges for a Future Reproductive Medicine

Since 1978, with the first IVF (in vitro fertilization) baby birth in Manchester (England), more than eight million IVF babies have been born throughout the world, and many new techniques and discoveries have emerged in reproductive medicine. To summarize the modern technology and progress in reproductive medicine, all scientific papers related to reproductive medicine, especially papers related to reproductive translational medicine, were fully searched, manually curated and reviewed. Results indicated whether male reproductive medicine or female reproductive medicine all have made significant progress, and their markers have experienced the progress from karyotype analysis to single-cell omics. However, due to the lack of comprehensive databases, especially databases collecting risk exposures, disease markers and models, prevention drugs and effective treatment methods, the application of the latest precision medicine technologies and methods in reproductive medicine is limited.

Congenital absence of the vas deferens with hypospadias or without hypospadias: Phenotypic findings and genetic considerations

Congenital absence of the vas deferens (CAVD) is a major cause of obstructive azoospermia. Mutations of CFTR and ADGRG2 cause the majority of CAVD. Despite this, 10%–20% of CAVD patients remain without a clear genetic diagnosis. Herein, the CFTR and ADGRG2 genes were first sequenced using Sanger sequencing in 50 CAVD patients. Whole-exome sequencing (WES) was used to further identify potential novel genetic causes in CAVD with hypospadias. In total, 29 of 50 CAVD patients carried at least one CFTR mutation, but no ADGRG2 mutation was found. 5T was found to be the most frequent variant in our CAVD populations. Seven CAVD patients with hypospadias were further analyzed using WES. No homozygous or compound heterozygous mutations related to disorders of sex development (DSDs) or male infertility were identified by WES. CAVD with hypospadias presented lower testicular volume (9.71 ± 2.14 ml vs. 14.45 ± 2.93 ml, p &lt; 0.001) and higher FSH level (FSH: 7.28 ± 3.91 IU/L vs. 4.24 ± 1.96 IU/L, p = 0.027) than CAVD without hypospadias. It is worth noting that neither CFTR or ADGRG2 mutation nor homozygous or compound heterozygous gene mutations were identified in seven CAVD cases with hypospadias. However, nine heterozygous or hemizygous mutations were selected as potential pathogenic genes in CAVD with hypospadias. In conclusion, CFTR variants, especially 5T, play a major role in the Chinese CAVD population. CAVD with hypospadias shows relatively lower testicular spermatogenesis, suggesting a different genetic basis or pathogenic factor from cystic fibrosis/CAVD or unilateral renal agenesis/CAVD.

Clinical Utility of Medical Exome Sequencing: Expanded Carrier Screening for Patients Seeking Assisted Reproductive Technology in China

Purpose: Expanded carrier screening (ECS) is an effective method to identify at-risk couples (ARCs) and avoid birth defects. This study aimed to reveal the carrier spectrum in the Chinese population and to delineate an expanded carrier gene panel suitable in China.

Methods: Medical exome sequencing (MES), including 4,158 disease-causing genes, was offered to couples at two reproductive centers. It was initially used as a diagnostic yield for potential patients and then used for ECS. Clinical information and ECS results were retrospectively collected.

Results: A total of 2,234 couples, representing 4,468 individuals, underwent MES. In total, 254 individuals showed genetic disease symptoms, and 56 of them were diagnosed with genetic diseases by MES. Overall, 94.5% of them were carriers of at least one disease-causing variant. The most prevalent genes were GJB2 for autosomal recessive disorders and G6PD for X-linked diseases. The ARC rate was 9.80%, and couples were inclined to undergo preimplantation genetic testing when diseases were classified as “profound” or “severe.”

Conclusion: This study provided insight to establish a suitable ECS gene panel for the Chinese population. Disease severity significantly influenced reproductive decision-making. The results highlighted the importance of conducting ECS for couples before undergoing assisted reproductive technology.

C FTR variants are associated with chronic bronchitis in smokers

INTRODUCTION

Loss-of-function variants in both copies of the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF); however, there is evidence that reduction in CFTR function due to the presence of one deleterious variant can have clinical consequences. Here, we hypothesise that CFTR variants in individuals with a history of smoking are associated with chronic obstructive pulmonary disease (COPD) and related phenotypes.

METHODS

Whole-genome sequencing was performed through the National Heart, Lung, and Blood Institute TOPMed (TransOmics in Precision Medicine) programme in 8597 subjects from the COPDGene (Genetic Epidemiology of COPD) study, an observational study of current and former smokers. We extracted clinically annotated CFTR variants and performed single-variant and variant-set testing for COPD and related phenotypes. Replication was performed in 2118 subjects from the ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints) study.

RESULTS

We identified 301 coding variants within the CFTR gene boundary: 147 of these have been reported in individuals with CF, including 36 CF-causing variants. We found that CF-causing variants were associated with chronic bronchitis in variant-set testing in COPDGene (one-sided p=0.0025; OR 1.53) and in meta-analysis of COPDGene and ECLIPSE (one-sided p=0.0060; OR 1.52). Single-variant testing revealed that the F508del variant was associated with chronic bronchitis in COPDGene (one-sided p=0.015; OR 1.47). In addition, we identified 32 subjects with two or more CFTR variants on separate alleles and these subjects were enriched for COPD cases (p=0.010).

CONCLUSIONS

Cigarette smokers who carry one deleterious CFTR variant have higher rates of chronic bronchitis, while presence of two CFTR variants may be associated with COPD. These results indicate that genetically mediated reduction in CFTR function contributes to COPD related phenotypes, in particular chronic bronchitis.

A spectrum of recessiveness among Mendelian disease variants in UK Biobank

Recent work has found increasing evidence of mitigated, incompletely penetrant phenotypes in heterozygous carriers of recessive Mendelian disease variants. We leveraged whole-exome imputation within the full UK Biobank cohort (n ∼ 500K) to extend such analyses to 3,475 rare variants curated from ClinVar and OMIM. Testing these variants for association with 58 quantitative traits yielded 102 significant associations involving variants previously implicated in 34 different diseases. Notable examples included a POR missense variant implicated in Antley-Bixler syndrome that associated with a 1.76 (SE 0.27) cm increase in height and an ABCA3 missense variant implicated in interstitial lung disease that associated with reduced FEV1/FVC ratio. Association analyses with 1,134 disease traits yielded five additional variant-disease associations. We also observed contrasting levels of recessiveness between two more-common, classical Mendelian diseases. Carriers of cystic fibrosis variants exhibited increased risk of several mitigated disease phenotypes, whereas carriers of spinal muscular atrophy alleles showed no evidence of altered phenotypes. Incomplete penetrance of cystic fibrosis carrier phenotypes did not appear to be mediated by common allelic variation on the functional haplotype. Our results show that many disease-associated recessive variants can produce mitigated phenotypes in heterozygous carriers and motivate further work exploring penetrance mechanisms.

Genetic analysis and intracytoplasmic sperm injection outcomes of Chinese patients with congenital bilateral absence of vas deferens

PURPOSE

Congenital bilateral absence of the vas deferens (CBAVD) is a major cause of obstructive azoospermia and male factor infertility. CBAVD is mainly caused by mutations in the genes encoding CFTR (cystic fibrosis transmembrane conductance regulator) and ADGRG2 (adhesion G protein-coupled receptor G2). This study aimed to describe CFTR and ADGRG2 variations in 46 Chinese CBAVD patients and evaluated sperm retrieval and assisted reproductive technology outcomes.

METHODS

The CFTR and ADGRG2 genes were sequenced and analyzed by whole-exome sequencing (WES), and variations were identified by Sanger sequencing. Bioinformatic analysis was performed. We retrospectively reviewed the outcomes of patients undergoing sperm retrieval surgery and intracytoplasmic sperm injection (ICSI).

RESULTS

In total, 35 of 46 (76.09%) patients carried at least one variation in CFTR, but no copy number variants or ADGRG2 variations were found. In addition to the IVS9-5 T allele, there were 27 CFTR variations, of which 4 variations were novel and predicted to be damaging by bioinformatics. Spermatozoa were successfully retrachieved in 46 patients, and 39 of the patients had their own offspring through ICSI.

CONCLUSION

There are no obvious hotspot CFTR mutations in Chinese CBAVD patients besides the IVS9-5 T allele. Therefore, WES might be the best detection method, and genetic counseling should be different from that provided to Caucasian populations. After proper counseling, all patients can undergo sperm retrieval from their epididymis or testis, and most of them can have their own children through ICSI.

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.

Precision Medicine Based on CFTR Genotype for People with Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive genetic condition that is caused by variants in the cystic fibrosis transmembrane conductance regulator gene. This causes multisystem disease due to dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) ion channel at the apical surface of epithelia. Until recently, treatment was directed at managing the downstream effects in affected organs, principally improving airway clearance and treating infection in the lungs and improving malabsorption in the gastrointestinal tract. Care delivered by multidisciplinary teams has yielded incremental improvements in outcomes. However, the development of small-molecule CFTR modulator drugs over the last decade has heralded a new era of CF therapeutics. Modulators target the underlying defect and improve CFTR function. Either monotherapy or a combination of modulators is used depending on the specific genotype and class of CFTR disease-causing variants that an individual has. Both ivacaftor and the ivacaftor/tezacaftor/elexacaftor combination have been demonstrated to be associated with clinically very significant benefits in randomised trials and have rapidly been made available as part of standard care in many countries. CFTR modulators represent one of the best examples of precision medicine to date. They are expensive, however, and equity of access to them worldwide remains an issue. Studies and approvals are also ongoing for children under the age of 6 years for ivacaftor/tezacaftor/elexacaftor. Furthermore, no modulators are available for around 10% of the people with CF. In this review, we firstly summarise the genetics, pathophysiology and clinical problems associated with CF. We then discuss the development of CFTR modulators and key clinical trials to support their use along with other potential future therapeutic approaches.

Clinical Phenotypes of Cystic Fibrosis Carriers

Cystic fibrosis (CF) is an autosomal recessive genetic disorder caused by mutations in CFTR, the cystic fibrosis transmembrane conductance regulator gene. People with CF experience a wide variety of medical conditions that affect the pulmonary, endocrine, gastrointestinal, pancreatic, biliary, and reproductive systems. Traditionally, CF carriers, with one defective copy of CFTR, were not thought to be at risk for CF-associated diseases. However, an emerging body of literature suggests that heterozygotes are at increased risk for many of the same conditions as homozygotes. For example, heterozygotes appear to be at increased risk for chronic pancreatitis, atypical mycobacterial infections, and bronchiectasis. In the United States alone, there are almost 10 million CF carriers. Universal newborn screening and prenatal genetic screening will identify more. Thus, there is a critical need to develop more precise estimates of health risks attributable to the CF carrier state across the lifespan.

The Changing Face of Cystic Fibrosis: An Update for Anesthesiologists

Cystic fibrosis (CF) is the most common fatal genetic disease in North America. While CF is more common among Whites, it is increasingly being recognized in other races and ethnicities. Although there is no cure, life expectancy has steadily improved, with the median survival exceeding 46 years in the United States. There are now more adults than children with CF in the United States. CF is caused by mutations in a gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) protein, expressed in many epithelial cells. More than 2100 CFTR mutations have been linked to CF, and newer CFTR modulator drugs are being used to improve the production, intracellular processing, and function of the defective CFTR protein. CF is a multisystem disease that affects primarily the lungs, pancreas, hepatobiliary system, and reproductive organs. Anesthesiologists routinely encounter CF patients for various surgical and medical procedures, depending on the age group. This review article focuses on the changing epidemiology of CF, advances in the classification of CFTR mutations, the latest innovations in CFTR modulator therapies, the impact of the coronavirus disease pandemic, and perioperative considerations that anesthesiologists must know while caring for patients with CF.

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.

A review of cystic fibrosis: Basic and clinical aspects

Cystic fibrosis is an autosomal recessive disease caused by mutations of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). Here we summarize, at the basic descriptive level, clinical and genetic characteristics of cystic fibrosis gene mutations, while emphasizing differences between CF mutations found in Chinese pediatric CF patients compared to those found in Caucasian CF patients. In addition, we describe animal models used to study human cystic fibrosis disease and highlight unique features of each model that mimic specific human CF-associated signs and symptoms. At the clinical level, we summarize CF clinical manifestations and diagnostic, treatment, and prognostic methods to provide clinicians with information toward reducing CF misdiagnosis and missed diagnosis rates.

Challenging the dogma of the healthy heterozygote: Implications for newborn screening policies and practices

Heterozygous (carrier) status for an autosomal recessive condition is traditionally considered to lack significance for an individual's health, but this assumption has been challenged by a growing body of evidence. Carriers of several autosomal recessive disorders and some X-linked diseases are potentially at risk for the pathology manifest in homozygotes. This minireview provides an overview of the literature regarding health risks to carriers of two common autosomal recessive conditions on the Recommended Uniform Screening Panel: sickle cell disease [sickle cell trait (SCT)] and cystic fibrosis (CF). We also consider and comment on bioethical and policy implications for newborn blood screening (NBS). Health risks for heterozygotes, while relatively low for individuals, are often influenced by intrinsic (e.g., other genomic variants or co-morbidities) and extrinsic (environmental) factors, which present opportunities for personalized genomic medicine and risk counseling. They create a special challenge, however, for developing screening/follow-up policies and for genetic counseling, particularly after identification and reporting of heterozygote status through NBS. Although more research is needed, this minireview of the SCT and CF literature to date leads us to propose that blanket terms such as "healthy heterozygotes" or "unaffected carriers" should be superseded in communications about NBS results, in favor of a more nuanced paradigm of setting expectations for health outcomes with "genotype-to-risk." In the molecular era of NBS, it remains clear that public health needs to become better prepared for the full range of applied genetics.

Antisense oligonucleotide-based drug development for Cystic Fibrosis patients carrying the 3849+10 kb C-to-T splicing mutation

Background:

Antisense oligonucleotide (ASO)-based drugs for splicing modulation were recently approved for various genetic diseases with unmet need. Here we aimed to develop an ASO-based splicing modulation therapy for Cystic Fibrosis (CF) patients carrying the 3849 + 10 kb C-to-T splicing mutation in the CFTR gene.

Methods:

We have screened, in FRT cells expressing the 3849 + 10 kb C-to-T splicing mutation, ~30 2ʹ-O-Methyl-modified phosphorothioate ASOs, targeted to prevent the recognition and inclusion of a cryptic exon generated due to the mutation. The effect of highly potent ASO candidates on the splicing pattern, protein maturation and CFTR function was further analyzed in well differentiated primary human nasal and bronchial epithelial cells, derived from patients carrying at least one 3849 + 10 kb C-to-T allele.

Results:

A highly potent lead ASO, efficiently delivered by free uptake, was able to significantly increase the level of correctly spliced mRNA and completely restore the CFTR function to wild type levels in cells from a homozygote patient. This ASO led to CFTR function with an average of 43% of wild type levels in cells from various heterozygote patients. Optimized efficiency of the lead ASO was further obtained with 2ʹ-Methoxy Ethyl modification (2ʹMOE).

Conclusion:

The highly efficient splicing modulation and functional correction, achieved by free uptake of the selected lead ASO in various patients, demonstrate the ASO therapeutic potential benefit for CF patients carrying splicing mutations and is aimed to serve as the basis for our current clinical development.

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.

[Cystic fibrosis: From gene discovery to precision medicine]

The discovery in 1989 that cystic fibrosis, the most common life-shortening hereditary disease in Caucasians, was caused by mutations in cystic fibrosis transmembrane conductance regulator (CFTR) gene, put in motion whole new areas of research, diagnosis, and therapeutic development. In this review, we focus on the most important advances in our understanding of the molecular basis of CFTR dysfunction. To date, over 2,000 CFTR mutations belonging to six protein-defect classes have been identified, increasing vastly our understanding of genotype/phenotype correlations. In the last 30 years, major achievements have been made in neonatal screening, antenatal diagnosis, and crucially with recent breakthroughs in the development of CFTR-directed therapies that may be effective for 90% of patients, paving the way for precision medicine.

Andrological findings in infertile men with two (biallelic) CFTR mutations: results of a multicentre study in Germany and Austria comprising 71 patients

STUDY QUESTION

When should cystic fibrosis transmembrane conductance regulator (CFTR) mutation analysis be recommended in infertile men based on andrological findings?

SUMMARY ANSWER

CFTR mutation analysis is recommended in all men with unexplained azoospermia in the presence of normal gonadotropin levels.

WHAT IS KNOWN ALREADY

While 80-97% of men with congenital bilateral absence of the vas deferens (CBAVD) are thought to carry CFTR mutations, there is uncertainty about the spectrum of clinical and andrological abnormalities in infertile men with bilallelic CFTR mutations. This information is relevant for evidence-based recommendations to couples requesting assisted reproduction.

STUDY DESIGN, SIZE, DURATION

We studied the andrological findings of patients with two CFTR mutations who were examined in one of the cooperating fertility centres in Germany and Austria. In the period of January till July 2019, the completed and anonymized data sheets of 78 adult male patients were returned to and analysed by the project leader at the Institute of Human Genetics in Innsbruck, Austria.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Minimum study entry criteria were the presence of two (biallelic) CFTR mutations and results of at least one semen analysis. Andrological assessments were undertaken by standardized data sheets and compared with normal reference values. Seventy-one patients were eligible for the study (n = 30, 42% from Germany, n = 26, 37% from Austria, n = 15, 21% other nations).

MAIN RESULTS AND THE ROLE OF CHANCE

Gonadotropin levels (FSH, LH) were normal, 22% of patients had reduced testosterone values. Mean right testis volume was 23.38 ml (SD 8.77), mean left testis volume was 22.59 ml (SD 8.68) and thereby statistically increased compared to normal (P < 0.01). although the means remained in the reference range of 12-25 ml. Semen analysis revealed azoospermia in 70 of 71 (99%) patients and severe oligozoospermia <0.1 × 106/ml in one patient. Four semen parameters, i.e. ejaculate volume, pH, α-glucosidase and fructose values, were significantly reduced (P < 0.01). Only 18% of patients had a palpatory and sonographically diagnosed CBAVD, while in 31% the diagnosis of CBAVD was uncertain, in 12% patients, the vas deferens was present but hypoplastic, and in 39% the vas deferens was normally present bilaterally. Seminal vesicles were not detectable in 37% and only unilaterally present in 37% of patients. Apart from total testes volume, clinical findings were similar in patients with two confirmed pathogenic CFTR mutations (Group I) compared with patients who carried one pathogenic mutation and one CFTR variant of unknown significance (Group II).

LIMITATIONS, REASONS FOR CAUTION

We could not formally confirm the in trans position of genetic variants in most patients as no family members were available for segregation studies. Nonetheless, considering that most mutations in our study have been previously described without other rare variants in cis, and in view of the compatible andrological phenotype, it is reasonable to assume that the biallelic genotypes are correct.

WIDER IMPLICATIONS OF THE FINDINGS

Our study reveals that CFTR mutation analysis has a broader indication than just the absence of the vas deferens. We recommend to completely sequence the CFTR gene if there is a suspicion of obstructive azoospermia, and to extend this analysis to all patients with unexplained azoospermia in the presence of normal gonadotropin levels.

STUDY FUNDING/COMPETING INTEREST(S)

German Research Foundation Clinical Research Unit 'Male Germ Cells: from Genes to Function' (DFG CRU326, grants to F.T.). There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Molecular analysis of CFTR gene mutations among Iraqi cystic fibrosis patients

Background

Cystic fibrosis (CF) is an autosomal recessive multisystem disease that results from mutation(s) of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. More than 2100 mutations and polymorphisms have been reported in this gene so far. Incidence and genotyping of CF are under-identified in Iraq. This study aims to determine the types and frequencies of certain CFTR mutations among a sample of Iraqi CF patients. Two groups of patients were included: 31 clinically confirmed CF patients in addition to 47 clinically suspected patients of CF. All confirmed patients had typical, moderate-severe clinical presentation and course of the disease. Molecular analysis was performed on the majority of enrolled patients using the CF-stripAssay® kit supplied by ViennaLab diagnostics, GmbH, Austria.

Results

The mutation-detection rate from the tested 34 mutations in this study was 19.5% and the 8 detected mutations were as follows: 3120+1G>A and W1282X were found in 3 (4.17%) patients each; F508del and R1162X were found in 2 (2.78%) patients each; 3272-26A>G, R347P, I507del, and 2183AA>G were found in 1 (1.38%) patient each. Polymorphic variants of IVS8, namely 5T, 7T, and 9T, were detected in ~ 70%. These results were nearly similar to what was reported in regional countries.

Conclusion

Cystic fibrosis seems to be not rare as previously thought. 3120+1G>A and W1282X are the two most commonly detected mutations. F508del needs to be included in all future tests, while the I507del mutation was uniquely reported in this study but not in regional studies.

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.

Genetics of CFTR and male infertility

Cystic fibrosis (CF) is a rare autosomal-recessive disorder manifested as multisystem organ dysfunction. The cystic fibrosis transmembrane conductance regulator (CFTR) protein functions as an ion transporter on the epithelium of exocrine glands, regulating secretion viscosity. The CFTR gene, encoded on chromosome 7, is required for the production and trafficking of the intact and functional CFTR protein. Literally thousands of human CFTR allelic mutations have been identified, each with varying impact on protein quality and quantity. As a result, individuals harboring CFTR mutations present with a spectrum of symptoms ranging from CF to normal phenotypes. Those with loss of function but without full CF may present with CFTR-related disorders (CFTR-RDs) including male infertility, sinusitis, pancreatitis, atypical asthma and bronchitis. Studies have demonstrated associations between higher rates of CFTR mutations and oligospermia, epididymal obstruction, congenital bilateral absence of the vas deferens (CBAVD), and idiopathic ejaculatory duct obstruction (EDO). Genetic variants are detected in over three-quarters of men with CBAVD, the reproductive abnormality most classically associated with CFTR aberrations. Likewise, nearly all men with clinical CF will have CBAVD. Current guidelines from multiple groups recommend CFTR screening in all men with clinical CF or CBAVD though a consensus on the minimum number of variants for which to test is lacking. CFTR testing is not recommended as routine screening for men with other categories of infertility. While available CFTR panels include 30 to 96 of the most common variants, complete gene sequencing should be considered if there is a high index of suspicion in a high-risk couple (e.g., partner is CFTR mutation carrier). CF treatments to date have largely targeted end-organ complications. Novel CFTR-modulator treatments aim to directly target CFTR protein dysfunction, effectively circumventing downstream complications, and possibly preventing symptoms like vasal atresia at a young age. Future gene therapies may also hold promise in preventing or reversing genetic changes that lead to CF and CFTR-RD.

Genetic testing for men with infertility: techniques and indications

Genetic testing is an integral component in the workup of male infertility as genetic conditions may be responsible for up to 15% of all cases. Currently, three genetic tests are commonly performed and recommended by major urologic associations: karyotype analysis (KA), Y-chromosome microdeletion testing, and CFTR mutation testing. Despite widespread adoption of these tests, an etiology for infertility remains elusive in up to 80% of cases. Recent work has identified intriguing new targets for genetic testing which may soon see clinical relevance. This review will discuss the indications and techniques for currently offered genetic tests and briefly explore ongoing research directions within this field.

How do we counsel men with obstructive azoospermia due to CF mutations?-a review of treatment options and outcomes

Obstructive azoospermia (OA) is a rare cause of male infertility, with Congenital Bilateral Absence of The Vas Deferens (CBAVD) being a major cause. A wealth of literature has established an irrefutable link between CFTR mutations and CBAVD, with CBAVD affecting almost all men with cystic fibrosis (CF) disease and a significant portion of men that are CFTR mutation carriers. In the past two decades, assisted reproductive technologies have made the prospect of fathering children a viable possibility in this subset of men, using a combination of sperm extraction techniques and intracystoplasmic sperm injection (ICSI). In order to assess techniques for sperm retrieval, as well as reproductive outcomes, a systemic search of the MEDLINE database was conducted for all articles pertaining to management options for CBAVD, and also all reports describing outcomes of these procedures in the CBAVD population. Both epididymal and testicular sperm extraction (TESE) are viable options for men with CBAVD, and though rigorous data are lacking, live birth rates range from 8% to 50% in most small retrospective series and subset analyses. In addition, there does not appear to be significant differences in the rate of live birth or complications and miscarriages between the various techniques, though further investigation into other factors that limit reproductive potential of men with CFTR mutations and CBAVD is warranted.

Genes Regulating Spermatogenesis and Sperm Function Associated With Rare Disorders

Spermatogenesis is a cell differentiation process that ensures the production of fertilizing sperm, which ultimately fuse with an egg to form a zygote. Normal spermatogenesis relies on Sertoli cells, which preserve cell junctions while providing nutrients for mitosis and meiosis of male germ cells. Several genes regulate normal spermatogenesis, some of which are not exclusively expressed in the testis and control multiple physiological processes in an organism. Loss-of-function mutations in some of these genes result in spermatogenesis and sperm functionality defects, potentially leading to the insurgence of rare genetic disorders. To identify genetic intersections between spermatogenesis and rare diseases, we screened public archives of human genetic conditions available on the Genetic and Rare Diseases Information Center (GARD), the Online Mendelian Inheritance in Man (OMIM), and the Clinical Variant (ClinVar), and after an extensive literature search, we identified 22 distinct genes associated with 21 rare genetic conditions and defective spermatogenesis or sperm function. These protein-coding genes regulate Sertoli cell development and function during spermatogenesis, checkpoint signaling pathways at meiosis, cellular organization and shape definition during spermiogenesis, sperm motility, and capacitation at fertilization. A number of these genes regulate folliculogenesis and oogenesis as well. For each gene, we review the genotype–phenotype association together with associative or causative polymorphisms in humans, and provide a description of the shared molecular mechanisms that regulate gametogenesis and fertilization obtained in transgenic animal models.

Multidisciplinary approach to patients with manifestations and pulmonary complications of cystic fibrosis

Cystic fibrosis (CF) is a genetic disease, with autosomal recessive transmission, multisystemic, characterized by a remarkable clinical polymorphism and significant lethal prospective. Respiratory manifestations dominate the clinical picture, being present in all patients. The aim of the paper was to analyze the incidence of clinical manifestations, especially respiratory ones, as well as the contribution of interdisciplinary consultations to the positive diagnosis of CF, in a group of 16 patients who were hospitalized and treated in the II^nd Pediatric Clinic and II^nd Medical Clinic of the Emergency County Hospital, Craiova, Romania, in a period of 20 years. The 16 patients diagnosed with and treated of CF had all shown increased values of sweat chloride concentration of over 60 mmol/L. The main symptoms and clinical signs encountered in these patients were cough (75%), sputum (62.5%), dyspnea (50%), wheezing (50%), stature hypotrophy (100%), pallor (37.5%), cyanosis (25%). All 16 patients had an acute exacerbation of chronic pulmonary disease. Of the total hospitalizations, the death was recorded only in the case of one female patient. The association of some clinical aspects specific with a positive result of the sweat test or the presence of the two pathological alleles made room for determining a positive diagnosis. The multisystemic nature of this disease requires a multidisciplinary approach to these patients. Histopathologically, there was a correspondence between lung morphological lesions and the results of imaging investigations.

Pharmacogenomics with red cells: a model to study protein variants of drug transporter genes

The PharmacoScan pharmacogenomics platform screens for variation in genes that affect drug absorption, distribution, metabolism, elimination, immune adverse reactions and targets. Among the 1,191 genes tested on the platform, 12 genes are expressed in the red cell membrane: ABCC1, ABCC4, ABCC5, ABCG2, CFTR, SLC16A1, SLC19A1, SLC29A1, ATP7A, CYP4F3, EPHX1 and FLOT1. These genes represent 5 ATP-binding cassette proteins, 3 solute carrier proteins, 1 ATP transport protein and 3 genes associated with drug metabolism and adverse drug reactions. Only ABCG2 and SLC29A1 encode blood group systems, JR and AUG, respectively. We propose red cells as an ex vivo model system to study the effect of heritable variants in genes encoding the transport proteins on the pharmacokinetics of drugs. Altered pharmacodynamics in red cells could also cause adverse reactions, such as haemolysis, hitherto unexplained by other mechanisms.

Quantitative Evaluation of CFTR Pre-mRNA Splicing Dependent on the (TG)mTn Poly-Variant Tract

Genetic analysis in cystic fibrosis (CF) is a difficult task. Within the many causes of variability and uncertainty, a major determinant is poor knowledge of the functional effect of most DNA variants of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. In turn, knowledge of the effect of a CFTR variant has dramatic diagnostic, prognostic and, in the era of CF precision medicine, also therapeutic consequences. One of the most challenging CFTR variants is the (TG)mTn haplotype, which has variable functional effect and controversial clinical consequences. The exact quantification of the anomalous splicing of CFTR exon 10 (in the HGVS name; exon 9 in the legacy name) and, consequently, of the residual wild-type functional CFTR mRNA, should be mandatory in clinical assessment of patients with potentially pathological haplotype of this tract. Here, we present a real time-based assay for the quantification of the proportion of exon 10+/exon 10− CFTR mRNA, starting from nasal brushing. Our assay proved rapid, economic and easy to perform. Specific primers used for this assay are either disclosed or commercially available, allowing any laboratory to easily perform it. A simplified analysis of the data is provided, facilitating the interpretation of the results. This method helps to enhance the comprehension of the genotype–phenotype relationship in CF and CFTR-related disorders (CFTR-RD), crucial for the diagnosis, prognosis and personalized therapy of CF.

Male infertility due to testicular disorders

CONTEXT

Male infertility is defined as the inability to conceive following 1 year of regular unprotected intercourse. It is the causative factor in 50% of couples and a leading indication for assisted reproductive techniques (ART). Testicular failure is the most common cause of male infertility, yet the least studied to date.

EVIDENCE ACQUISITION

The review is an evidence-based summary of male infertility due to testicular failure with a focus on etiology, clinical assessment, and current management approaches. PubMed-searched articles and relevant clinical guidelines were reviewed in detail.

EVIDENCE SYNTHESIS/RESULTS

Spermatogenesis is under multiple levels of regulation and novel molecular diagnostic tests of sperm function (reactive oxidative species and DNA fragmentation) have since been developed, and albeit currently remain as research tools. Several genetic, environmental, and lifestyle factors provoking testicular failure have been elucidated during the last decade; nevertheless, 40% of cases are idiopathic, with novel monogenic genes linked in the etiopathogenesis. Microsurgical testicular sperm extraction (micro-TESE) and hormonal stimulation with gonadotropins, selective estrogen receptor modulators, and aromatase inhibitors are recently developed therapeutic approaches for men with the most severe form of testicular failure, nonobstructive azoospermia. However, high-quality clinical trials data is currently lacking.

CONCLUSIONS

Male infertility due to testicular failure has traditionally been viewed as unmodifiable. In the absence of effective pharmacological therapies, delivery of lifestyle advice is a potentially important treatment option. Future research efforts are needed to determine unidentified factors causative in "idiopathic" male infertility and long-term follow-up studies of babies conceived through ART.

Disease gene discovery in male infertility: past, present and future

Identifying the genes causing male infertility is important to increase our biological understanding as well as the diagnostic yield and clinical relevance of genetic testing in this disorder. While significant progress has been made in some areas, mainly in our knowledge of the genes underlying rare qualitative sperm defects, the same cannot be said for the genetics of quantitative sperm defects. Technological advances and approaches in genomics are critical for the process of disease gene identification. In this review we highlight the impact of various technological developments on male infertility gene discovery as well as functional validation, going from the past to the present and the future. In particular, we draw attention to the use of unbiased genomics approaches, the development of increasingly relevant functional assays and the importance of large-scale international collaboration to advance disease gene identification in male infertility.

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.

Analysis of CNVs of CFTR gene in Chinese Han population with CBAVD

Background

Congenital bilateral absence of vas deferens (CBAVD) is an important disease of male infertility, which affects 1%–2% of infertile population. In addition to common mutations of CFTR, copy number variants (CNVs) have also been implicated as one of the pathogenesis of CBAVD. The present study aimed to investigate the genetic contribution of CFTR CNVs in Chinese Han population with CBAVD.

Methods

Two hundred and sixty‐three CBAVD patients were recruited. Genomic DNA was extracted from peripheral blood samples. The Multiplex Ligation‐dependent Probe Amplification assay was performed which targets the region of the CFTR gene.

Results

Among 263 Chinese men affected with CBAVD in this study, 5 (1.90%) patients were detected for copy number variants in the region of CFTR gene (4 of them carried partial deletions and 1 of them carried partial duplication of CFTR gene).

Conclusions

The study showed that the rate of CFTR CNVs in Chinese population with CBAVD were basically consistent with the previous reports. And the study first revealed genetic risk of CNVs of CFTR on a large sample size of CBAVD patients in Chinese Han population, which prompted that it was necessary to detect CNVs of CFTR in Chinese Han people with CBAVD.

Mutations of the cystic fibrosis transmembrane conductance regulator gene in males with congenital bilateral absence of the vas deferens: Reproductive implications and genetic counseling (Review)

Congenital bilateral absence of the vas deferens (CBAVD) is predominantly caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CBAVD accounts for 2–6% of male infertility cases and up to 25% of cases of obstructive azoospermia. With the use of pre-implantation genetic diagnosis, testicular or epididymal sperm aspiration, intracytoplasmic sperm injection and in vitro fertilization, patients affected by CBAVD are able to have children who do not carry CFTR gene mutations, thereby preventing disease. Therefore, genetic counseling should be provided to couples receiving assisted reproductive techniques to discuss the impact of CFTR gene mutations on reproductive health. In the present article, the current literature concerning the CFTR gene and its association with CBAVD is reviewed.

Mutation analysis of the cystic fibrosis transmembrane conductance regulator gene in Chinese congenital absence of vas deferens patients

To find the variant spectrum of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and evaluate its frequent variants in Chinese congenital absence of vas deferens (CAVD) patients. A total of 276 patients with azoospermia and CAVD (aged from 21 to 44 years old) were investigated from May 2013 to September 2019 in the Third Affiliated Hospital of Sun Yat-sen University. Additionally, 50 healthy, unrelated volunteers were recruited as controls (aged from 21 to 46 years old). The 5'-UTR, exons and their flanking side of the CFTR gene were sequenced by high-throughput sequencing technology. The results were compared with those retrieved from the Ensembl Genome Browser. In addition, all 13 novel variants were further confirmed independently by Sanger sequencing and evaluated in the bioinformatics web servers. A schematic of the variant spectrum of the CFTR gene, including 13 novel variants (12 in CAVD patients, one in the control group), is shown, and the frequent variants in Chinese CAVD patients were 5 T (27.54%), c.-8G > C (7.25%), p.Q1352H (5.98%), and p.I556V (3.08%). 5 T was found to be the most frequent variant. p.Q1352H had a significantly high allelic frequency in CAVD patients (P < 0.05). c.-8G > C and p.I556V had high allelic frequencies but showed no difference between patients and controls (P > 0.05). p.Q1352H is the most common and important missense variant in Chinese patients with CAVD, while the pathological effects of C.-8G > C and p.I556V may be weak after evaluation.

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.

Characterization of clinical and genetic spectrum of Chinese patients with cystic fibrosis

Background

Cystic fibrosis (CF) is a rare autosomal recessive disorder caused by biallelic mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The clinical features and mutation spectrum of CF have been well characterized in Caucasians, while limited studies were conducted in Chinese patients.

Subjects and methods

A total of 20 individuals from 19 families were diagnosed with CF in this study. We analyzed the clinical features and screened all coding exons of CFTR using a combination of Sanger sequencing and multiplex ligation-dependent probe amplification analysis.

Results

The median age at onset was 9.3 years in our cohort, while the median age at diagnosis was 19 years. The respiratory system was most frequently affected in this study: all patients (100%, 19/19) presented diffuse bronchiectasis and 61.1% (11/18) of patients showed a forced expiratory volume in 1 s below 80% predicted. Six patients (6/20, 30%) exhibited allergic bronchopulmonary aspergillosis (ABPA). Only 4 (4/20, 20%) patients presented pancreatic exocrine insufficiency (PI). Three adult male patients receiving examinations for congenital bilateral absence of the vas deferens were all found positive for the condition. A total of 22 distinct mutations were detected in this cohort, with the variant p.G970D as the most common variant (12/38 alleles, 31.6%). Four variants (p.Y109D, p.I203F, p.D572E, and exon 2–3 deletion) were novel, which expanded the mutation spectrum of Chinese CF patients.

Conclusions

Chinese CF patients showed different clinical features and a distinct CFTR mutation spectrum compared with Caucasians. There is a significant diagnosis delay, suggesting the current underdiagnosis of CF in China.

Haplotype analysis of the CFTR gene on normal and mutant CFTR genes

BACKGROUND

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are responsible for Cystic Fibrosis (CF) disease. Since the distribution of polymorphisms varies among populations, a comparison between the frequency of CFTR polymorphisms in patients and healthy population may further identify their role in CF disease. The results obtained from this research may facilitate the prediction of disease phenotype in prenatal diagnosis or newborn screening program as well as determine the possible associations between haplotypes and specific mutations.

METHODS

Blood samples collected from 27 unrelated West Iranian families contain at least one CF patient and 55 control families with no history of CF. Samples were analyzed for c.1210-12 T [5-9], c.1242-35-1242-12GT [8-10], c.744-33GATT [6-8] and c.869 + 11C > T polymorphisms by automated direct DNA sequencing following DNA extraction.

RESULTS

Our results showed that the T7 allele is the most common allele in normal and non-ΔF508 CF chromosomes with the frequencies of 93.6% and 100%, respectively. Conversely, T9 was the only allele detected in ΔF508 chromosomes. Moreover, the c.1242-35-1242-12GT analysis showed that (TG)11 repeat was the most common dinucleotide repeat in both, non-ΔF508 and normal chromosomes with the frequencies of 91% and 71%, respectively. The c.744-33GATT and c.869 + 11C > T polymorphism analyses indicated that (GATT)6 and T allele are only found in ΔF508 CF chromosomes. Besides, the [T7-TG11-GATT7-C] haplotype was the most common haplotype in both, normal and non-ΔF508 CF subjects while the [T9-TG10- GATT6-T] haplotype was only detected in CF patients carrying ΔF508 mutation.

CONCLUSIONS

Our findings identified an informative haplotype that could be used in genetic counseling, prenatal diagnosis and future screening of CF in Iran.