CFTR mutation screening in an assisted reproductive clinic

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.

Preventable Hazards from in Vitro Fertilization - A Case Series of CF Patients from Bulgaria

Pre-implantation genetic diagnosis (PGD) is not often performed when donor gametes are used, due to its high cost. This is with the presumption that the donors are healthy. We report on five cases of babies with confirmed cystic fibrosis (CF), being the result from in vitro fertilization (IVF) with donor (4 cases) or own gametes (one case). There has been no family history for CF in any of the families affected. The clinical presentation in the children ranged from meconium ileus to recurrent respiratory infections and severe nasal polyposis. The age of diagnosis also varied from birth until 9 years. Since one of the presented cases was discovered in a very renowned private IVF clinic, the clinic changed their own protocol, and currently they test every donor for CF carriership. The percentage of CF carriers in the donor population is roughly the same as the one predicted in the general population of Bulgaria - 1/33. Although PGD is costly, the costs for proper care for a CF patient are currently much higher. The more economical option would to screen every donor for CF carriership. IVF requires a lot of physical and psychological stamina. The couples that go through this procedure also require a great deal of hope. It is essential to be more preconscious for possible congenital diseases. We advocate every IVF center to test the donors for CF carriership or to provide PGD for their clients.

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.

Cystic fibrosis transmembrane conductance regulator in follicular fluid and cumulus cells and its relationship with age

Oocyte quality deteriorates with female age and numerous indicators of oocyte quality exist. In the present study, the levels of cystic fibrosis transmembrane conductance regulator (CFTR) in the follicular fluid (FF) and cumulus cells (CCs) of infertile females in 3 different age groups were assessed to determine the relationship between CFTR and female age. The general features of the 3 groups, including age, body mass index, infertility duration, basal hormone levels and the number of retrieved oocytes were compared. The FF CFTR levels of the 3 groups were also compared and multiple age-related indicators of oocyte quality were analyzed, including the estradiol levels on the human chorionic gonadotropin injection day, the morphologically normal oocyte rate and the available or high-quality embryo rate. Immunofluorescence and PCR analyses were performed to examine CFTR expression in CCs around oocytes. The results indicated differences in general features and several indicators of oocyte quality among the 3 groups and significant differences in CFTR. The FF CFTR level was positively correlated with age, which was confirmed by immunofluorescence and PCR. Collectively, these results indicated that CFTR expression in FF and CCs may be associated with oocyte quality based on the age of individuals undergoing the assisted reproduction technique.

Genetics in human reproduction

Approximately 50% of the causes of infertility are of genetic origin. The objective of this study was to analyze the role of genetics in human reproduction by reviewing the main genetic causes of infertility and the use of preimplantation genetic testing in Brazil. This literature review comprised articles in English and Portuguese published on databases PubMed, Scielo, and Bireme from 1990 to 2019. Randomized clinical trials and specialized guidelines were given preference whenever possible. Genetic cause can be traced back to up to 20% of the cases of severe azoospermia or oligozoospermia. Subjects with these conditions are good candidates for genetic screening. In women, genetic causes of infertility (fragile X syndrome, X-trisomy, and Turner's syndrome, some of which diagnosed with karyotyping) culminate with premature ovarian failure. Genetic screening helps advise couples of the risk of experiencing early reproductive capacity loss and of the chances of their offspring carrying genetic disorders. In addition to enhancing the prevention of serious diseases in the offspring of couples at increased risk of genetic diseases, preimplantation genetic screening improves the success rates of assisted reproduction procedures by allowing the selection of euploid embryos for transfer. The interface between genetics and human reproduction has gained significant relevance, but discussions are still needed on which procedures are clinically and ethically acceptable and how they should be regulated.

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.

Scrotal Ultrasonic Features of Congenital Bilateral Absence of Vas Deferens

OBJECTIVE

This article discusses scrotal ultrasonic features of patients with a congenital bilateral absence of the vas deferens (CBAVD).

METHODS

Thirty-six patients with CBAVD were examined to obtain image characteristics of the bilateral testicle and epididymis by ultrasound. Each patient received a pathological examination of the sperm by percutaneous epididymal biopsy.

RESULTS

Scrotal ultrasonic features were as follows: (1) testicular volumes were normal in all the 36 patients; (2) 21% (15/72) of the heads of epididymis, 67% (48/72) of the heads and bodies of epididymis, and 12% (9/72) of the heads, bodies, and tails of epididymis could be shown in the 72 epididymides of the 36 patients; (3) cystic or tubular dilation of the epididymis was obvious in all 72 abnormal epididymides; and (4) bilateral vas deferens could not be found in these patients. Johnsen's grading of sperm in all the 36 patients received a score of 7 or higher (scale of 10, lower numbers denote greater dysfunction).

CONCLUSIONS

Ultrasonography images of the scrotum revealed characteristics that were commonly present in patients with CBAVD. Therefore, this method is helpful to diagnose CBAVD by identifying the features of epididymis structural abnormalities and cystic or tubular dilation of the epididymis.

Differential Diagnostic Value of Obstructive and Nonobstructive Azoospermia by Scrotal Ultrasound

Our objective was to assess the differential diagnostic value of classification of obstructive versus nonobstructive azoospermia by scrotal ultrasound. Forty patients with azoospermia were selected for our study (ages, 23-35; average, 29 ± 5.34 years). Patients were divided into the obstructive (17) or nonobstructive (23) azoospermia category. Twenty "healthy" volunteers were selected for the control group. We observed the testis, epididymis, and vas deferens in all subjects. Testicular volumes were calculated and compared with the control group for both obstructive and nonobstructive groups. Cystic or tubular dilation of the epididymis was found in all patients with obstructive azoospermia. The patients with nonobstructive azoospermia had no significant abnormalities of the epididymis. There was no difference in the testicular volumes between the patients with obstructive azoospermia and healthy controls (P > 0.05). However, the testicular volumes of patients with nonobstructive azoospermia were smaller than those of healthy volunteers (P < 0.05). It is helpful to identify obstructive and nonobstructive azoospermia by scrotal ultrasound, because it is a less invasive method that can be used to isolate probable treatment options.

Preimplantation genetic diagnosis for cystic fibrosis: a case report

Cystic fibrosis is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator gene. This disorder produces a variable phenotype including lung disease, pancreatic insufficiency, and meconium ileus plus bilateral agenesis of the vas deferens causing obstructive azoospermia and male infertility. Preimplantation genetic diagnosis is an alternative that allows identification of embryos affected by this or other genetic diseases. We report a case of couple with cystic fibrosis; the woman had the I148 T mutation and the man had the Delta F508 gene mutation. The couple underwent in vitro fertilization, associated with preimplantation genetic diagnosis, and with subsequent selection of healthy embryos for uterine transfer. The result was an uneventful pregnancy and delivery of a healthy male baby.

Clinical diagnostic Next-Generation sequencing: the case of CFTR carrier screening

A 23-mutation panel for CFTR carrier screening is recommended to women of reproductive age by the American College of Obstetricians and Gynecologists. In the present study the optimized efficiency regarding the carrier rate of Next-Generation sequencing (NGS) technology is compared to the one of limited mutation detection panels. A total of 824 consequent cases were subjected to the commercial Cystic Fibrosis Genotyping Assay. Some 188 negative samples randomly selected from the initial group of probands were further subjected to an extended mutation panel characterized by 92% detection rate, as well as to massive parallel sequencing. Twenty-two probands subjected to the commercial assay proved to carry one mutation included in the ACOG panel (carrier rate 0.0267). The latter panels revealed the presence of mutations not included in the ACOG panel in four probands, resulting to an increase of carrier rate of 0.0106 in the case of in-house panel and an increase of rate of 0.0213 if NGS was used. The above data seem to support the implementation of NGS in the routine CFTR carrier screening.

Prenatal and preconception population carrier screening for cystic fibrosis in Australia: where are we up to?

AIMS

To describe prenatal and preconception population carrier screening for cystic fibrosis (CF) in Australia and consider progress towards establishing a universal program.

METHOD

Medline and Embase databases (1989-2013) were searched for all publications with Australian data. Existing programs for CF carrier screening in Australia were reviewed and professional peak body websites accessed to determine recommendations.

RESULTS

Twenty-two studies met the inclusion criteria. Key stakeholder groups believe that prenatal and preconception carrier screening for CF should be available. Health-economic analyses support that CF carrier screening can be cost-effective. There are small programs for CF carrier screening, in Victoria, New South Wales and Queensland. The Human Genetics Society of Australasia (HGSA) specifically recommend that screening be offered to women and couples planning a pregnancy and in the early stages of pregnancy. Other peak bodies indirectly endorse the availability of CF carrier screening. Barriers to screening include not being offered screening, the cost of testing, inequity of access and an incorrect perception that not having a family history of CF lowers risk.

CONCLUSIONS

There is support for prenatal and preconception CF carrier screening by the community, health professionals and peak professional bodies in Australia. The barriers to development of a national screening program could be overcome with greater physician engagement and government support.

IMPLICATIONS

In the interest of equity, government funded testing should be routinely offered to all pregnant women and couples planning a pregnancy.

Relevance of genetic investigation in male infertility

Genetic causes can be directly responsible for various clinical conditions of male infertility and spermatogenic impairment. With the increased use of assisted reproduction technologies our understanding of genetic basis of male infertility has large implications not only for understanding the causes of infertility but also in determining the prognosis and management of such couples. For these reasons, the genetic investigations represent today an essential and useful tool in the treatment of male infertility. Several evidences are available for the clinical practice regarding the diagnosis; however, there are less information relative to the treatment of the genetic causes of male infertility. Focus of this review is to discuss the main and more common genetic causes of male infertility to better direct the genetics investigation in the treatment of spermatogenic impairment.

Ion/Water Channels for Embryo Implantation Barrier

Successful implantation involves three distinct processes, namely the embryo apposition, attachment, and penetration through the luminal epithelium of the endometrium to establish a vascular link to the mother. After penetration, stromal cells underlying the epithelium differentiate and surround the embryo to form the embryo implantation barrier, which blocks the passage of harmful substances to the embryo. Many ion/water channel proteins were found to be involved in the process of embryo implantation. First, ion/water channel proteins play their classical role in establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane. Second, most of ion/water channel proteins are regulated by steroid hormone (estrogen or progesterone), which may have important implications to the embryo implantation. Last but not least, these proteins do not limit themselves as pure channels but also function as an initiator of a series of consequences once activated by their ligand/stimulator. Herein, we discuss these new insights in recent years about the contribution of ion/water channels to the embryo implantation barrier construction during early pregnancy.

Cystic fibrosis carrier screening

Carrier screening for cystic fibrosis (CF) has been available since the early 1990s, yet there are few programs, and none funded as part of a national health care strategy. The aim of this paper is to provide a description of carrier screening for CF and examine the progress that has been made towards the establishment of universal population-based carrier screening programs. This is an evidence based commentary on population-based carrier screening for CF. Peak body recommendations were examined and existing programs for CF carrier screening are reviewed. The attitudes from the non-CF community, CF healthcare professionals and people with CF were studied. Data from health economic assessments is examined. The future of carrier screening for CF in the context of advancing genetic technologies and potentially curative therapies is considered.