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

Male Fertility as a Proxy for Health

Male fertility is affected by a wide range of medical conditions that directly and indirectly affect spermatogenesis. As such, it can be useful as both an indicator of current health and a predictive factor for future health outcomes. Herein, we discuss the current literature regarding the association between male fertility and systemic health conditions and exposures. We review the connection between male fertility and genetics, medications, diet, and environmental pollutants, as well as its effects on future oncologic, cardiovascular, and autoimmune conditions. Understanding this interplay will allow more health care providers to engage in health counseling that will not only improve men's reproductive outcomes but also their overall health.

An overview of CFTR mutation profiles and assisted reproductive technology outcomes in Chinese patients with congenital obstructive azoospermia

PURPOSE

The cystic fibrosis transmembrane conductance regulator (CFTR) is the most common causative gene attributed to congenital obstructive azoospermia (OA). The aim of this study was to conduct an epidemiological survey of congenital OA patients, to screen for CFTR mutations, and to follow their pregnancy outcomes in assisted reproductive technology (ART).

METHODS

This cohort study enrolled congenital OA patients undergoing ART and whole-exome sequencing from January 2018 to September 2023. Semen parameters, sex hormones, and seminal plasma biochemistry were evaluated. CFTR mutations identified in OA patients were analyzed. In addition, the laboratory outcomes, clinical outcomes, and neonatal outcomes were compared between OA patients carrying two CFTR mutations and the others after surgical sperm extraction-intracytoplasmic sperm injection (ICSI) treatment.

RESULTS

A total of 76 patients with congenital OA were enrolled. CFTR mutations were identified in 35 (46.1%) congenital OA patients. A total of 60 CFTR mutation sites of 27 types were identified, and 10 of them were novel. The average frequency was 1.71 (60/35) per person. The most common mutation was c.1210-11T > G (25%, 15/60). After ICSI treatment, there were no statistically significant differences in laboratory outcomes, clinical outcomes, and neonatal outcomes between OA patients carrying two CFTR mutations (n = 25) and other OA patients (n = 51).

CONCLUSION

Apart from the IVS9-5T mutation, the genetic mutation pattern of CFTR in Chinese OA patients is heterogeneous, which is significantly different from that of Caucasians. Although carrying two CFTR mutations or not had no effect on the pregnancy outcomes in OA patients after ICSI, genetic counseling is still recommended for such patients.

Compound heterozygous mutations in CFTR causing congenital bilateral absence of the vas deferens in a Chinese pedigree

BACKGROUND

Cystic fibrosis (CF) is an autosomal recessive disorder rarely found in Asian populations. Most males with CF are infertile because of obstructive azoospermia (OA) caused by congenital bilateral absence of the vas deferens (CBAVD). Compound heterozygous mutations of cystic fibrosis transmembrane conductance regulator (CFTR) are among the most common pathogenic factors in CBAVD. However, few genealogical analyses have been performed.

METHODS

In this study, whole-exome sequencing and cosegregation analysis were performed in a Chinese pedigree involving two siblings with CBAVD. Moreover, in vitro gene expressions were used to analyze the pathogenicity of a novel CFTR mutation.

RESULTS

We identified compound heterozygous mutations of CFTR comprising the known disease-causing variant c.1210-11T>G (also known as IVS9-5 T) and c.2144delA;p.q715fs in two siblings with CBAVD. To verify the effects in vitro, we transfected vectors expressing wild-type and mutated CFTR into 293T cells. The results showed that the CFTR protein containing the frameshift mutation (c.2144delA) was 60 kD smaller. With testicular sperm aspiration/intracytoplasmic sperm injection-embryo transfer (TESA/ICSI-ET), both CBAVD patients fathered healthy offspring.

CONCLUSION

Our study revealed that compound heterozygous mutations of CFTR are involved in CBAVD, expanding the known CFTR gene mutation spectrum of CBAVD patients and providing more evidence that compound heterozygous mutations can cause familial CBAVD.

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.

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

In brief

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

Abstract

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

Mutations in CFTR genes are associated with oligoasthenospermia in infertile men undergoing IVF

Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation has been clearly defined in congenital absence of the vas deferens (CAVD), which is an important cause of obstructive azoospermia. However, the association between oligoasthenospermia and CFTR gene mutation remains controversial. To confirm this issue, 151 infertile Chinese men were screened for CFTR mutation by NGS approach, including 18 CAVD patients, 72 patients with severe oligoasthenospermia and 61 controls with normal sperm parameters. Frequency of mutation in exons of CFTR gene were 66.7% in CAVD patients (12/18) (p < 0.001) and 8.33% in severe oligoasthenospermic patients (6/72) (p < 0.05), both of which were significantly more frequent than that in the controls (0/61). In terms of introns mutation of CFTR gene, there was no significant difference in frequency of 5T between oligoasthenospermic men (5/144, 3.47%) and the controls (4/122, 3.28%) (p = 0.645). In addition, 6 novel mutations in exons of CFTR gene in this study (c.3736A>G, c.635T>G, c.482delA, c.1858C>T, c.2042A>T, c.1586A>C) have not been reported in the Cystic Fibrosis Mutation Database before. Thus, our study provides evidence that CFTR gene mutation may be the aetiology of severe oligoasthenospermia other than CAVD. It may be necessary to screen for CFTR mutations in men with severe oligoasthenospermia before receiving assisted reproductive technology.

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.

Male fertility as a marker for health

Male reproduction is a complex biological process, and male factor infertility is increasingly recognized as a biomarker for overall male health. Emerging data suggest associations between male reproduction and medical disease (genetic, infectious, chronic comorbid conditions), psychological disease, environmental exposures, dietary habits, medications and substances of abuse, and even socioeconomic factors. There is also evidence that a diagnosis of male fertility is associated with future disease risk including cancer, metabolic disease and mortality. As such, there is a growing view that the male fertility evaluation is an opportunity to improve a man's health beyond his immediate reproductive goals, and also highlights the necessity of a multidisciplinary approach.

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

BACKGROUND

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

DISCUSSION AND CONCLUSIONS

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

New insights to guide patient care: the bidirectional relationship between male infertility and male health

Male reproduction is a complex process, and numerous medical conditions have the potential to alter spermatogenesis. In addition, male factor infertility may be a biomarker for future health. In the present review, we discuss the current literature regarding the association between systemic diseases and fertility, which may impact clinical outcomes or semen parameters. A number of conditions that have systemic consequences were identified, including genetic (e.g., cystic fibrosis, DNA mismatch repair alterations), obesity, psychological stress, exogenous testosterone, and a variety of common medications. As such, the infertility evaluation may offer an opportunity for health counseling beyond the discussion of reproductive goals. Moreover, male infertility has been suggested as a marker of future health, given that poor semen parameters and a diagnosis of male infertility are associated with an increased risk of hypogonadism, cardiometabolic disease, cancer, and even mortality. Therefore, male fertility requires multidisciplinary expertise for evaluation, treatment, and counseling.

Genetics of the congenital absence of the vas deferens

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

A novel mutation (-195C>A) in the promoter region of CFTR gene is associated with Chinese Congenital Bilateral Absence of Vas Deferens (CBAVD)

Congenital bilateral absence of vas deferens (CBAVD), a frequent cause of obstructive azoospermia and male infertility in Chinese, is mainly due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This study aim to explore the promoter region of CFTR gene in CBAVD patients and study the mutations by functional analysis, and to discuss the significance of mutation testing in this area. We performed screening analysis on 65 CBAVD patients and 50 controls to detect mutations in the CFTR gene, and studied the functions of promoter mutations using reporter gene constructs, transient transfection techniques and subsequent assessment of transcriptional activity and expression levels. Mutations c.-195C>A and c.-34C>T in the promoter region of the CFTR gene were detected in 4 of our Chinese CBAVD patients, one of which was novel (c.-195C>A) and located in the conservative area, as well as the binding site of SP1 transcription factor through the prediction of bioinformatics analysis. By reverse transcription qPCR assay and luciferase assay, we validated it as a functional disease-causing variant that down-regulates the CFTR gene expression, and this effect was related to the amount of transcription factors. This study was the first to explore the promoter region of the CFTR gene in Chinese, and we believe that mutations in this region are associated with Chinese CBAVD patients. We also suggest a systematic strategy for genotyping Chinese CBAVD couples, which should help in developing reproductive counseling.

Associations between DNAH1 gene polymorphisms and male infertility: A retrospective study

Genetic abnormalities could account for 10% to 15% of male infertility cases, so increasing attention is being paid to gene mutations in this context. DNAH1 gene polymorphisms are highly correlated with astheno-teratozoospermia, but limited information has been reported on pathogenic variations in DNAH1 in the Chinese population. We explored 4 novel variations of the DNAH1 gene in Chinese infertile patients. Mutation screening of the DNAH1 gene was performed on 87 cases of asthenozoospermia with targeted high-throughput sequencing technology; another 200 nonobstructive azoospermia cases were further analyzed to investigate the prevalence of DNAH1 variations. The effects of the variations on protein function were further assessed by bioinformatic prediction. For carriers of DNAH1 variations, genetic counseling should be considered. Assisted reproductive technologies should be performed for these individuals and microsurgery should be considered for patients with azoospermia. DNAH1 variations were identified in 6 of 287 patients. These included 8 heterozygous variations in exons and a splicing site. Among these, 4 variations (g.52400764G>C, g.52409336C>T, g.52430999_52431000del, g.52412624C>A) had already been registered in the 1000 Genomes and Exome Aggregation Consortium databases. The other 4 novel variations (g.52418050del, g.52404762T>G, g.52430536del, g.52412620del) were all predicted to be pathogenic by in silico analysis. The variations g.52418050del and g.52430999_52431000del were detected in 1 patient who was more severe than another patient with the variation g.52430999_52431000del. Physicians should be aware of genetic variants in male infertility patients and DNAH1 mutations should be considered in patients with asthenospermia or azoospermia.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Novel function of LHFPL2 in female and male distal reproductive tract development

Congenital reproductive tract anomalies could impair fertility. Female and male reproductive tracts are developed from Müllerian ducts and Wolffian ducts, respectively, involving initiation, elongation and differentiation. Genetic basis solely for distal reproductive tract development is largely unknown. Lhfpl2 (lipoma HMGIC fusion partner-like 2) encodes a tetra-transmembrane protein with unknown functions. It is expressed in follicle cells of ovary and epithelial cells of reproductive tracts. A spontaneous point mutation of Lhfpl2 (LHFPL2^G102E) leads to infertility in 100% female mice, which have normal ovarian development, ovulation, uterine development, and uterine response to exogenous estrogen stimulation, but abnormal upper longitudinal vaginal septum and lower vaginal agenesis. Infertility is also observed in ~70% mutant males, which have normal mating behavior and sperm counts, but abnormal distal vas deferens convolution resulting in complete and incomplete blockage of reproductive tract in infertile and fertile males, respectively. On embryonic day 15.5, mutant Müllerian ducts and Wolffian ducts have elongated but their duct tips are enlarged and fail to merge with the urogenital sinus. These findings provide a novel function of LHFPL2 and a novel genetic basis for distal reproductive tract development; they also emphasize the importance of an additional merging phase for proper reproductive tract development.