PGD for cystic fibrosis patients and couples at risk of an additional genetic disorder combined with 24-chromosome aneuploidy testing

ISPD 2021 Debate - All IVF cycles should involve pre-implantation genetic testing to improve fetal health and pregnancy outcomes

For three decades, couples at increased risk for a genetic disorder have been offered preimplantation genetic testing (PGT). Simultaneously, PGT for aneuploidy (PGT-A) to improve in vitro fertilization (IVF) outcomes was introduced, but evidence of value-added remains inconsistent. Recently, lower genetic testing costs and shorter turnaround time have reinvigorated PGT-A. Additionally, a shift from blastomere (day 3) to blastocyst (day 5) transfer and embryo freezing advances support PGT without the time constraints of immediate transfer. PGT-A transformed from a time-constrained analysis of 1-2 cells to an "add on" study for all IVF. But should it be offered to all IVF patients? And if not, under what conditions? Pre-debate polling found 64% opposed to PGT for all IVF cycles with concerns voiced about cost, informed consent, and a "slippery slope". Leaving aside the inconsistent evidence of IVF improvement whether measured as miscarriage or livebirths with PGT-A, the debaters grappled with patient and provider desires versus the ethical concerns for the unborn child. However, the audience was not swayed; two thirds remained opposed to PGT for all IVF cycles. This article is protected by copyright. All rights reserved.

Preimplantation genetic testing for carriers of BRCA1/2 pathogenic variants

The detection of germline BRCA1/2 pathogenic variant has relevant implications for the patients and their family members. Family planning, prophylactic surgery and the possibility of preimplantation genetic testing for monogenic disorders (PGT-M) to avoid transmittance of pathogenic variants to the offspring are relevant topics in this setting. PGT-M is valuable option for BRCA carriers, but it remains a controversial and underdiscussed topic. Although the advances in PGT technologies have improved pregnancy rate, there are still several important challenges associated with its use. The purpose of this review is to report the current evidence on PGT-M for BRCA1/2 carriers, ethical concerns and controversy associated with its use, reproductive implications of BRCA pathogenic variants, underlying areas in which an educational effort would be beneficial as well as possibilities for future research efforts in the field.

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.

Preimplantation Genetic Testing for Monogenic Kidney Disease

BACKGROUND AND OBJECTIVES

A genetic cause can be identified for an increasing number of pediatric and adult-onset kidney diseases. Preimplantation genetic testing (formerly known as preimplantation genetic diagnostics) is a reproductive technology that helps prospective parents to prevent passing on (a) disease-causing mutation(s) to their offspring. Here, we provide a clinical overview of 25 years of preimplantation genetic testing for monogenic kidney disease in The Netherlands.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is a retrospective cohort study of couples counseled on preimplantation genetic testing for monogenic kidney disease in the national preimplantation genetic testing expert center (Maastricht University Medical Center+) from January 1995 to June 2019. Statistical analysis was performed through chi-squared tests.

RESULTS

In total, 98 couples were counseled regarding preimplantation genetic testing, of whom 53% opted for preimplantation genetic testing. The most frequent indications for referral were autosomal dominant polycystic kidney disease (38%), Alport syndrome (26%), and autosomal recessive polycystic kidney disease (9%). Of couples with at least one preimplantation genetic testing cycle with oocyte retrieval, 65% experienced one or more live births of an unaffected child. Of couples counseled, 38% declined preimplantation genetic testing for various personal and technical reasons.

CONCLUSIONS

Referrals, including for adult-onset disease, have increased steadily over the past decade. Though some couples decline preimplantation genetic testing, in the couples who proceed with at least one preimplantation genetic testing cycle, almost two thirds experienced at least one live birth rate.

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.

Preimplantation Genetic Testing: Where We Are Today

BACKGROUND

Preimplantation genetic testing (PGT) is widely used today in in-vitro fertilization (IVF) centers over the world for selecting euploid embryos for transfer and to improve clinical outcomes in terms of embryo implantation, clinical pregnancy, and live birth rates.

METHODS

We report the current knowledge concerning these procedures and the results from different clinical indications in which PGT is commonly applied.

RESULTS

This paper illustrates different molecular techniques used for this purpose and the clinical significance of the different oocyte and embryo stage (polar bodies, cleavage embryo, and blastocyst) at which it is possible to perform sampling biopsies for PGT. Finally, genetic origin and clinical significance of embryo mosaicism are illustrated.

CONCLUSIONS

The preimplantation genetic testing is a valid technique to evaluated embryo euploidy and mosaicism before transfer.

Multicenter validation study for the certification of a CFTR gene scanning method using next generation sequencing technology

BACKGROUND

Many European laboratories offer molecular genetic analysis of the CFTR gene using a wide range of methods to identify mutations causative of cystic fibrosis (CF) and CFTR-related disorders (CFTR-RDs). Next-generation sequencing (NGS) strategies are widely used in diagnostic practice, and CE marking is now required for most in vitro diagnostic (IVD) tests in Europe. The aim of this multicenter study, which involved three European laboratories specialized in CF molecular analysis, was to evaluate the performance of Multiplicom's CFTR MASTR Dx kit to obtain CE-IVD certification.

METHODS

A total of 164 samples, previously analyzed with well-established "reference" methods for the molecular diagnosis of the CFTR gene, were selected and re-sequenced using the Illumina MiSeq benchtop NGS platform. Sequencing data were analyzed using two different bioinformatic pipelines. Annotated variants were then compared to the previously obtained reference data.

RESULTS AND CONCLUSIONS

The analytical sensitivity, specificity and accuracy rates of the Multiplicom CFTR MASTR assay exceeded 99%. Because different types of CFTR mutations can be detected in a single workflow, the CFTR MASTR assay simplifies the overall process and is consequently well suited for routine diagnostics.

Karyomapping and how is it improving preimplantation genetics?

INTRODUCTION

Preimplantation genetic diagnosis and screening (PGD/PGS) has been applied clinically for >25 years however inherent drawbacks include the necessity to tailor each case to the trait in question, and that technology to detect monogenic and chromosomal disorders respectively is fundamentally different. Areas covered: The area of preimplantation genetics has evolved over the last 25 years, adapting to changes in technology and the need for more efficient, streamlined diagnoses. Karyomapping allows the determination of inheritance from the (grand)parental haplobocks through assembly of inherited chromosomal segments. The output displays homologous chromosomes, crossovers and the genetic status of the embryos by linkage comparison, as well as chromosomal disorders. It also allows for determination of heterozygous SNP calls, avoiding the risks of allele dropout, a common problem with other PGD techniques. Manuscripts documenting the evolution of preimplantation genetics, especially those investigating technologies that would simultaneously detect monogenic and chromosomal disorders, were selected for review. Expert commentary: Karyomapping is currently available for detection of single gene disorders; ~1000 clinics worldwide offer it (via ~20 diagnostic laboratories) and ~2500 cases have been performed. Due an inability to detect post-zygotic trisomy reliably however and confounding problems of embryo mosaicism, karyomapping has yet to be applied clinically for detection of chromosome disorders.

Healthy Baby Born to a Robertsonian Translocation Carrier following Next-Generation Sequencing-Based Preimplantation Genetic Diagnosis: A Case Report

Preimplantation genetic diagnosis (PGD) is well established method for treatment of genetic problems associated with infertility. Moreover, PGD with next-generation sequencing (NGS) provide new possibilities for diagnosis and new parameters for evaluation in, for example, aneuploidy screening. The aim of the study was to report the successful pregnancy outcome following PGD with NGS as the method for 24 chromosome aneuploidy screening in the case of Robertsonian translocation. Day 3 embryos screening for chromosomal aneuploidy was performed in two consecutive in vitro fertilization (IVF) cycles, first with fluorescent in situ hybridization (FISH), and then with NGS-based protocol. In each IVF attempt, three embryos were biopsied. Short duration of procedures enabled fresh embryo transfer without the need for vitrification. First IVF cycle with the embryo selected using PGD analysis with the FISH method ended with pregnancy loss in week 8. The second attempt with NGS-based aneuploidy screening led to exclusion of the following two embryos: one embryo with 22 monosomy and one with multiple aneuploidies. The transfer of the only euploid blastocyst resulted in the successful pregnancy outcome. The identification of the euploid embryo based on the NGS application was the first successful clinical application of NGS-based PGD in the case of the Robertsonian translocation carrier couple.

Attitudes of cystic fibrosis patients and parents toward carrier screening and related reproductive issues

Cystic fibrosis (CF) is a life-limiting autosomal recessive disorder affecting ~1 in 2500-4000 Caucasians. As most CF patients have no family history of the disorder, carrier screening for CF has the potential to prospectively identify couples at risk of conceiving an affected child. At-risk couples may consequently choose to act on the provided information and take steps to avoid the birth of a child with CF. Although carrier screening is widely believed to enhance reproductive autonomy of prospective parents, the practice also raises important ethical questions. A written questionnaire was administered to adult patients and parents of children with CF with the aim to explore participants' attitudes toward CF carrier screening and related reproductive issues. The study population was recruited from a CF patient registry in Belgium and comprised 111 participants (64 parents, 47 patients aged 16 or older). We found that more than 80% of all participants were in favor of preconception carrier screening for CF. However, some were concerned over potential negative consequences of population-wide CF carrier screening. Regarding future reproductive intentions, 43% of the participants indicated a desire to have children. Among these, preimplantation genetic diagnosis was found to be the most preferred reproductive option, closely followed by spontaneous pregnancy and prenatal diagnosis. Although the findings of our study suggest that patients and parents of children with CF support a population-based carrier screening program for CF, they also highlight some issues deserving particular attention when implementing such a program.

Clinical utilisation of a rapid low-pass whole genome sequencing technique for the diagnosis of aneuploidy in human embryos prior to implantation

BACKGROUND

The majority of human embryos created using in vitro fertilisation (IVF) techniques are aneuploid. Comprehensive chromosome screening methods, applicable to single cells biopsied from preimplantation embryos, allow reliable identification and transfer of euploid embryos. Recently, randomised trials using such methods have indicated that aneuploidy screening improves IVF success rates. However, the high cost of testing has restricted the availability of this potentially beneficial strategy. This study aimed to harness next-generation sequencing (NGS) technology, with the intention of lowering the costs of preimplantation aneuploidy screening.

METHODS

Embryo biopsy, whole genome amplification and semiconductor sequencing.

RESULTS

A rapid (<15 h) NGS protocol was developed, with consumable cost only two-thirds that of the most widely used method for embryo aneuploidy detection. Validation involved blinded analysis of 54 cells from cell lines or biopsies from human embryos. Sensitivity and specificity were 100%. The method was applied clinically, assisting in the selection of euploid embryos in two IVF cycles, producing healthy children in both cases. The NGS approach was also able to reveal specified mutations in the nuclear or mitochondrial genomes in parallel with chromosome assessment. Interestingly, elevated mitochondrial DNA content was associated with aneuploidy (p<0.05), a finding suggestive of a link between mitochondria and chromosomal malsegregation.

CONCLUSIONS

This study demonstrates that NGS provides highly accurate, low-cost diagnosis of aneuploidy in cells from human preimplantation embryos and is rapid enough to allow testing without embryo cryopreservation. The method described also has the potential to shed light on other aspects of embryo genetics of relevance to health and viability.

Rare large homozygous CFTR gene deletion in an Iranian patient with cystic fibrosis

Cystic fibrosis, a common autosomal recessive genetic disorder among Caucasians, is caused by defects in the transmembrane conductance regulatory (CFTR) gene. The analysis of CFTR gene mutations is useful to better characterize the disease, and for preconceptional screening, prenatal and preimplantation genetic diagnosis. Here we report the results of a genetic analysis in a 16-year-old boy from southwestern Iran diagnosed as having cystic fibrosis in infancy based on gastrointestinal and pulmonary manifestations, with positive sweat chloride tests. He lacked both normal and mutant forms of the fragment corresponding to the ∆F508 allele in initial genetic studies. Multiplex ligation-dependent probe amplification-based testing revealed a homozygous deletion spanning exons 4 to 10 of the CFTR gene. We predict an in-frame deletion removing 373 amino acids based on our sequencing results. Determining CFTR gene mutations in patients and their family members would be helpful to prevent the occurrence of new cases, especially in populations in which consanguinity is common.

Live birth after PGD with confirmation by a comprehensive approach (karyomapping) for simultaneous detection of monogenic and chromosomal disorders

Preimplantation genetic diagnosis (PGD) for monogenic disorders has the drawback of time and cost associated with tailoring a specific test for each couple, disorder, or both. The inability of any single assay to detect the monogenic disorder in question and simultaneously the chromosomal complement of the embryo also limits its application as separate tests may need to be carried out on the amplified material. The first clinical use of a novel approach ('karyomapping') was designed to circumvent this problem. In this example, karyomapping was used to confirm the results of an existing PGD case detecting both chromosomal abnormalities and a monogenic disorder (Smith-Lemli-Opitz [SLO] syndrome) simultaneously. The family underwent IVF, ICSI and PGD, and both polar body and cleavage stage biopsy were carried out. Following whole genome amplification, array comparative genomic hybridisation of the polar bodies and minisequencing and STR analysis of single blastomeres were used to diagnose maternal aneuploidies and SLO status, respectively. This was confirmed, by karyomapping. Unlike standard PGD, karyomapping required no a-priori test development. A singleton pregnancy and live birth, unaffected with SLO syndrome and with no chromosome abnormality, ensued. Karyomapping is potentially capable of detecting a wide spectrum of monogenic and chromosome disorders and, in this context, can be considered a comprehensive approach to PGD.

Preimplantation genetic diagnosis for inherited neurological disorders

Preimplantation genetic diagnosis (PGD) is an option for couples at risk of having offspring with an inherited debilitating or fatal neurological disorder who wish to conceive a healthy child. PGD has been carried out for conditions with various modes of inheritance, including spinal muscular atrophy, Huntington disease, fragile X syndrome, and chromosomal or mitochondrial disorders, and for susceptibility genes for cancers with nervous system involvement. Most couples at risk of transmitting a genetic mutation would opt for PGD over prenatal testing and possible termination of a pregnancy. The aim of this Perspectives article is to assist neurologists in counselling and treating patients who wish to explore the option of PGD to enable conception of an unaffected child. PGD can be accomplished for most disorders in which the genetic basis is known, and we argue that it is time for clinicians and neurological societies to consider the evidence and to formulate guidelines for the responsible integration of PGD into modern preventative neurology.

Preimplantation genetic diagnosis for cystic fibrosis: the Montpellier center's 10-year experience

This study provides an overview of 10 years of experience of preimplantation genetic diagnosis (PGD) for cystic fibrosis (CF) in our center. Owing to the high allelic heterogeneity of CF transmembrane conductance regulator (CFTR) mutations in south of France, we have set up a powerful universal test based on haplotyping eight short tandem repeats (STR) markers together with the major mutation p.Phe508del. Of 142 couples requesting PGD for CF, 76 have been so far enrolled in the genetic work-up, and 53 had 114 PGD cycles performed. Twenty-nine cycles were canceled upon in vitro fertilization (IVF) treatment because of hyper- or hypostimulation. Of the remaining 85 cycles, a total of 493 embryos were biopsied and a genetic diagnosis was obtained in 463 (93.9%), of which 262 (without or with a single CF-causing mutation) were transferable. Twenty-eight clinical pregnancies were established, yielding a pregnancy rate per transfer of 30.8% in the group of seven couples with one member affected with CF, and 38.3% in the group of couples whose both members are carriers of a CF-causing mutation [including six couples with congenital bilateral absence of the vas deferens (CBAVD)]. So far, 25 children were born free of CF and no misdiagnosis was recorded. Our test is applicable to 98% of couples at risk of transmitting CF.