Place of preimplantation diagnosis in genetic practice

Evolution and Utility of Preimplantation Genetic Testing for Monogenic Disorders in Assisted Reproduction - A Narrative Review

Preimplantation genetic testing (PGT) for monogenic disorders and assisted reproductive technology have evolved and progressed in tandem. PGT started with single-cell polymerase chain reaction (PCR) followed by fluorescent in situ hybridisation for a limited number of chromosomes, later called 'preimplantation genetic diagnosis (PGD) version 1'. This review highlights the various molecular genetic techniques that have evolved to detect specific inherited monogenic disorders in the preimplantation embryo. Literature review in English was performed in PubMed from 1990 to 2021, using the term 'preimplantation genetic diagnosis'. With whole-genome amplification, multiple copies of embryonic DNA were created. This helped in avoiding misdiagnosis caused by allele dropout. Multiplex fluorescent PCR analysed informative short tandem repeats (STR) and detected mutations simultaneously on automated capillary electrophoresis sequencers by mini-sequencing. Comparative genomic hybridisation (CGH) and array CGH were used for 24 chromosome aneuploidy screening. Subsequently, aneuploidies were detected by next-generation sequencing using single-nucleotide polymorphism arrays, while STR markers were used for haplotyping. 'PGD version 2' included accurate marker-based diagnosis of most monogenic disorders and detection of aneuploidy of all chromosomes. Human leukocyte antigen matching of embryos has important implications in diagnosis and cure of haemoglobinopathies and immunodeficiencies in children by means of matched related haematopoietic stem cell transplantation from an unaffected 'saviour sibling' obtained by PGT.

Hormonal Effects in Reproductive Technology with Focus on Diminished Ovarian Reserve

Modern use of reproductive technologies has revolutionized the treatment of infertile couples. Strategies to improve ovarian function in cases of diminished ovarian reserve are perhaps the least understood area in this field and will be the chief focus of this chapter.

Effects of a carrier's sex and age on the segregation patterns of the trivalent of Robertsonian translocations

PURPOSE

To investigate the effects of a carrier's sex and age on the segregation patterns of the trivalent of Robertsonian translocations.

METHODS

This retrospective study was designed to analyze the segregation patterns of the trivalent and euploidy rates of blastocysts. Data were collected from 154 couples with Robertsonian translocation (77 with a female carrier and 77 with a male carrier). Embryos were diagnosed via array comparative genomic hybridization between January 2013 and July 2017. The segregation patterns of the trivalent of 604 blastocysts were analyzed according to the carrier's sex and age.

RESULTS

The proportion of alternate segregation was significantly higher (82.9% vs. 55.2%) in the male carriers than in the female carriers of Robertsonian translocation, and the proportion of adjacent segregation was significantly lower (16.8% vs. 42.6%), with no difference in 3:0 segregation. The segregation patterns were similar in same-sex carriers when analyzed according to the type of translocation. The carrier's age had no influence on the segregation patterns of the trivalent.

CONCLUSIONS

The proportions of the trivalent's meiotic segregation pattern differ significantly according to the carrier's sex in Robertsonian translocations and are independent of the carrier's age. A significantly higher proportion of alternate segregation for normal or balanced chromosome contents was observed in the blastocysts of the male carriers than in those of the female carriers.

Acceptable applications of preimplantation genetic diagnosis (PGD) among Israeli PGD users

The use of PGD technology to select against genetic disorders and traits is increasing. Although PGD may eliminate some of the obstacles related to conservative options of prenatal diagnosis, it can raise personal, social and moral questions. Ethical issues concerning the justified uses of PGD are a subject of ongoing debate among medical and bioethical communities. Although attitudes toward the acceptable uses of PGD were evaluated among population groups worldwide, bioethics councils were criticized for ignoring public perspectives. In the last decade PGD has been widely used in Israel. The ethical guidelines were created solely by medical-bioethics experts and, some felt, totally isolated from public opinions. Semi-structured in-depth interviews of 37 users (carriers of autosomal recessive, dominant and X-linked disorders, and HLA-matching) were performed. The interviews explored attitudes toward ethical and sociological aspects of PGD. The overall results of this study show highly favorable attitudes of Israeli PGD users toward medical applications. Furthermore, our subjects demonstrate a more permissive stand toward the controversial application of social sex selection albeit with strong objection to esthetic means of selection. PGD users are coping with both genetic disease and load of the PGD procedure. Taking into consideration their opinion is important since it reflects the gains and burdens of these procedures alongside the demand for future optional services. Their attitudes should play an important role in the professional discussion concerning the justified uses of PGD and should significantly influence the design of policy making in this field.

Factors Influencing the Decision-Making Process and Long-Term Interpersonal Outcomes for Parents Who Undergo Preimplantation Genetic Diagnosis for Fanconi Anemia: a Qualitative Investigation

Fanconi anemia (FA) is characterized by congenital malformations, progressive bone marrow failure, and predisposition to malignancy. Hematopoietic stem cell transplantation is used to treat FA, and best results are attained with sibling donors who are human leukocyte antigen (HLA) identical matches. Preimplantation genetic diagnosis (PGD) offers parents of an affected child the opportunity to have an unaffected child who is an HLA match. While some research has investigated parents' experiences during the PGD process, no published studies specifically address factors influencing their decision-making process and long-term interpersonal outcomes. The aims of this study are to: (1) examine parents' expectations and the influence of media, bioethics, and religion on their decision to undergo PGD; (2) examine parents' social support and emotional experiences during their PGD process; and (3) characterize long-term effects of PGD on relationship dynamics (partner, family, friends), others' attitudes, and parental regret. Nine parents participated in semi-structured interviews. Thematic analysis revealed their decision to use PGD was variously influenced by media, bioethics, and religion, in particular, affecting parents' initial confidence levels. Moreover, the PGD process was emotionally complex, with parents desiring varying amounts and types of support from different sources at different times. Parents reported others' attitudes towards them were similar or no different than before PGD. Parental regret regarding PGD was negligible. Results of this study will promote optimization of long-term care for FA families.

Outcomes of in vitro fertilization with preimplantation genetic diagnosis: an analysis of the United States Assisted Reproductive Technology Surveillance Data, 2011-2012

OBJECTIVE

To assess the characteristics of IVF cycles for which preimplantation genetic diagnosis (PGD) was used and to evaluate indications for PGD and treatment outcomes associated with this procedure as compared with cycles without PGD with the data from the U.S. National ART Surveillance System.

DESIGN

Retrospective cohort study.

SETTING

None.

PATIENT(S)

Fresh autologous cycles that involved transfer of at least one embryo at blastocyst when available.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

PGD indications and age-specific reproductive outcomes.

RESULT(S)

There were a total of 97,069 non-PGD cycles and 9,833 PGD cycles: 55.6% were performed for aneuploidy screening (PGD Aneuploidy), 29.1% for other reasons (PGD Other), and 15.3% for genetic testing (PGD Genetic). In comparison to non-PGD cycles, PGD Aneuploidy cycles showed a decreased odds of miscarriage among women 35-37 years (adjusted odds ratio [aOR] 0.62; 95% CI, 0.45-0.87) and women >37 years (aOR 0.55; 95% CI, 0.43-0.70); and an increased odds of clinical pregnancy (aOR 1.18; 95% CI, 1.05-1.34), live-birth delivery (aOR 1.43; 95% CI, 1.26-1.62), and multiple-birth delivery (aOR 1.98; 95% CI, 1.52-2.57) among women >37 years.

CONCLUSION(S)

Aneuploidy screening was the most common indication for PGD. Use of PGD was not observed to be associated with an increased odds of clinical pregnancy or live birth for women <35 years. PGD for aneuploidy was associated with a decreased odds of miscarriage for women >35 years, but an increased odds of a live-birth and a multiple live-birth delivery among women >37 years.

New advances of preimplantation and prenatal genetic screening and noninvasive testing as a potential predictor of health status of babies

The current morphologically based selection of human embryos for transfer cannot detect chromosome aneuploidies. So far, only biopsy techniques have been able to screen for chromosomal aneuploidies in the in vitro fertilization (IVF) embryos. Preimplantation genetic diagnosis (PGD) or screening (PGS) involves the biopsy of oocyte polar bodies or embryonic cells and has become a routine clinical procedure in many IVF clinics worldwide, including recent development of comprehensive chromosome screening of all 23 pairs of chromosomes by microarrays for aneuploidy screening. The routine preimplantation and prenatal genetic diagnosis (PND) require testing in an aggressive manner. These procedures may be invasive to the growing embryo and fetus and potentially could compromise the clinical outcome. Therefore the aim of this review is to summarize not only the new knowledge on preimplantation and prenatal genetic diagnosis in humans, but also on the development of potential noninvasive embryo and fetal testing that might play an important role in the future.

Preimplantation genetic screening (PGS) still in search of a clinical application: a systematic review

Only a few years ago the American Society of Assisted Reproductive Medicine (ASRM), the European Society for Human Reproduction and Embryology (ESHRE) and the British Fertility Society declared preimplantation genetic screening (PGS#1) ineffective in improving in vitro fertilization (IVF) pregnancy rates and in reducing miscarriage rates. A presumably upgraded form of the procedure (PGS#2) has recently been reintroduced, and is here assessed in a systematic review. PGS#2 in comparison to PGS#1 is characterized by: (i) trophectoderm biopsy on day 5/6 embryos in place of day-3 embryo biopsy; and (ii) fluorescence in-situ hybridization (FISH) of limited chromosome numbers is replaced by techniques, allowing aneuploidy assessments of all 24 chromosome pairs. Reviewing the literature, we were unable to identify properly conducted prospective clinical trials in which IVF outcomes were assessed based on "intent to treat". Whether PGS#2 improves IVF outcomes can, therefore, not be determined. Reassessments of data, alleged to support the efficacy of PGS#2, indeed, suggest the opposite. Like with PGS#1, the introduction of PGS#2 into unrestricted IVF practice again appears premature, and threatens to repeat the PGS#1 experience, when thousands of women experienced reductions in IVF pregnancy chances, while expecting improvements. PGS#2 is an unproven and still experimental procedure, which, until evidence suggests otherwise, should only be offered under study conditions, and with appropriate informed consents.

Heterozygosity assessment of five STR loci located at 5q13 region for preimplantation genetic diagnosis of spinal muscular atrophy

Preimplantation genetic diagnosis (PGD) has been considered as an alternative to prenatal diagnosis for prevention of genetic disorders while avoiding the subsequent termination of pregnancy. However, the limited amount of template DNA available in a single diploid cell used for PGD leads to number of problems including an increased incidence of detectable contamination; amplification failure and allele drop out. Due to their highly polymorphic and amplifiable characteristics, short tandem repeat (STR) analysis has been proposed as a mean to overcome these limitations. Heterozygosity of the applied STRs is of paramount importance in their informativity, and should therefore be studied in any certain population. Here, for the first time, we report on the heterozygosity analysis of five STR markers (D5S1408, D5S1417, D5S610, D5S629 and D5S637) flanking to SMA gene region, to examine their applicability in the PGD for SMA disease. We have also investigated other statistical features of these markers and found that all of the five studied STRs were informative and four meet the Hardy-Weinberg equilibrium for the studied population. Furthermore, our results propose that similar approaches can be used for the PGD of other single gene disorders.

Psychomotor development of children born after preimplantation genetic diagnosis and parental stress evaluation

BACKGROUND

The increasing number of children conceived following preimplantation genetic diagnosis (PGD) necessitates the evaluation of their motor and cognitive development. The primary study objective was to evaluate the physical, developmental, and neurological outcome of children born after PGD in Greece. In addition, the secondary study objective was to compare the stress levels regarding parental roles between parents of PGD children and those of naturally conceived children.

METHODS

A cross-sectional study design was applied. The study population consisted of 31 children (aged 2 months to 7.5 years) born after PGD analysis and their parents. The developmental evaluation of children included a detailed physical evaluation and cognitive assessment with the Bayley Scales of Infant Development. The parent stress index was applied to evaluate comparative parental stress levels between those parents of PGD children and those of naturally conceived healthy children.

RESULTS

High rates of caesarean deliveries, increased incidence of prematurity, multiples and low-birth weight were observed among the 31 PGD children. Overall, 24 of the 31 PGD children had cognitive skills within normal range [general developmental quotient (GDQ): 86-115], while 6 children had lower levels of cognitive skills (GDQ<85). With regard to parental stress, PGD parents reported lower levels of parenting stress as compared to parents of naturally conceived children (P<0.01).

CONCLUSIONS

The enhanced frequency of poor cognitive and motor skills as well as low parental stress necessitates early detection and intervention for developmental delays among PGD children.

[Genetics of first polar body]

The development of FISH and ART identified aneuploidy in polar body. The presence of these oocyte abnormalities conducts to implantation failure. The aim of the new technique is to select the best oocyte by complete chromosome analysis, and study of second polar body.

Strategies for future histocompatible stem cell therapy

Stem cell therapy based on the safe and unlimited self-renewal of human pluripotent stem cells is envisioned for future use in tissue or organ replacement after injury or disease. A gradual decline of regenerative capacity has been documented among the adult stem cell population in some body organs during the aging process. Recent progress in human somatic cell nuclear transfer and inducible pluripotent stem cell technologies has shown that patient-derived nuclei or somatic cells can be reprogrammed in vitro to become pluripotent stem cells, from which the three germ layer lineages can be generated, genetically identical to the recipient. Once differentiation protocols and culture conditions can be defined and optimized, patient-histocompatible pluripotent stem cells could be directed towards virtually every cell type in the human body. Harnessing this capability to enrich for given cells within a developmental lineage, would facilitate the transplantation of organ/tissue-specific adult stem cells or terminally differentiated somatic cells to improve the function of diseased organs or tissues in an individual. Here, we present an overview of various experimental cell therapy technologies based on the use of patient-histocompatible stem cells, the pending issues needed to be dealt with before clinical trials can be initiated, evidence for the loss and/or aging of the stem cell pool and some of the possible uses of human pluripotent stem cell-derivatives aimed at curing disease and improving health.

Adults with genetic syndromes and cardiovascular abnormalities: clinical history and management

Cardiovascular abnormalities, especially structural congenital heart defects, commonly occur in malformation syndromes and genetic disorders. Individuals with syndromes comprise a significant proportion of those affected with selected congenital heart defects such as complete atrioventricular canal, interrupted arch type B, supravalvar aortic stenosis, and pulmonary stenosis. As these individuals age, they contribute to the growing population of adults with special health care needs. Although most will require longterm cardiology follow-up, primary care providers, geneticists, and other specialists should be aware of (1) the type and frequency of cardiovascular abnormalities, (2) the range of clinical outcomes, and (3) guidelines for prospective management and treatment of potential complications. This article reviews fundamental genetic, cardiac, medical, and reproductive issues associated with common genetic syndromes that are frequently associated with a cardiovascular abnormality. New data are also provided about the cardiac status of adults with a 22q11.2 deletion and with Down syndrome.

Cord blood stem cell transplantation for haemoglobinopathies

Despite improvements in supportive care, patients with beta-thalassaemia major or sickle cell disease (SCD) may benefit from haematopoietic stem cell transplantation at some point during their lives. Human leucocyte antigen (HLA)-matched sibling bone marrow donors are not always available and alternative sources of stem cells have been sought, including related and unrelated donor cord blood transplants (CBT). The outcome of CBT from related donors for the treatment of both thalassaemia major and SCD is now approaching that for bone marrow transplantation, with around 90% of patients surviving disease-free. The main complication is graft rejection, which may be reduced by increasing pretransplant immune suppression. Transplant-related mortality following HLA-identical matched related donor CBT is extremely low but is significant in the small series of unrelated and/or mis-matched donor CBT. The principal limitation to extending the use of CB stem cells for the cure of haemoglobinopathies is the need to better understand the mechanisms of action and optimal conditioning regimens used to secure long-term engraftment while minimizing morbidity and mortality. Further biological studies and clinical trials are needed to address this aim.

PGD for aneuploidy screening: an expensive hoax?

Pre-implantation genetic diagnosis for aneuploidy screening (PGD-AS) constitutes a technique developed to improve embryo selection in patients with a poor outcome after in-vitro fertilization treatment due to an increased frequency of numerical chromosome abnormalities in the embryos. Although multiple studies have evaluated the performance of PGD-AS in different groups of patients, inconsistencies in the evidence available have not enabled definitive conclusions to be drawn. According to randomized trials, PGD-AS does not improve the outcome of women of advanced age when there is no limitation on the number of embryos to be transferred. In patients who have experienced recurrent implantation failure or recurrent miscarriage, AS only seems to provide diagnostic information, especially when aneuploid embryos alone are found. Additional evidence is needed before AS is implemented as part of routine clinical practice.

Preimplantation genetic diagnosis

This article covers the rapidly advancing field of preimplantation genetic diagnosis (PGD), the molecular genetic analysis of cells taken from embryos formed through in vitro fertilization (IVF). The article focuses on current practices in patient management, relevant IVF and PGD procedures, molecular methods used in the genetic analysis, and technical difficulties that can affect test results. It discusses the growing list of indications for PGD including chromosomal disorders, monogenic disorders and human leukocyte antigen typing typing of embryos. The article also examines some of the emerging technologies being introduced into PGD.

The paths around stem cell intellectual property

Can new approaches for deriving human stem cells circumnavigate existing patents that dominate embryonic stem cell intellectual property?

PGD patients' and providers' attitudes to the use and regulation of preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) providers and patients have a vested interest in policy related to the use and regulation of PGD. To understand their experiences and attitudes, 32 in-depth interviews were conducted. Participants included 13 people at risk of transmitting a single-gene alteration to their children (10/13 had actually used PGD to try to have an unaffected child) and 19 PGD service providers (four nurses, five genetic counsellors, two reproductive endocrinologists, two geneticists, two physician-geneticists, two embryologists, and two laboratory directors). Virtually all participants supported the use of PGD to avoid severe, life-threatening genetic illness or to select embryos that are a tissue match for a sick sibling, but their attitudes varied significantly over the appropriateness of using PGD to avoid adult-onset genetic disease, to select for sex, or to select for other non-medical characteristics. There was disagreement within the PGD provider community about whether or not PGD is experimental. Participants were more concerned about overzealous government regulation of PGD creating barriers to access than potential abuses of the technology, and expected the PGD provider community to take the lead in ensuring that PGD is used for ethically appropriate purposes.