Preimplantation genetic diagnosis and screening

Genetic counselling and testing in adults with congenital heart disease: A consensus document of the ESC Working Group of Grown-Up Congenital Heart Disease, the ESC Working Group on Aorta and Peripheral Vascular Disease and the European Society of Human Genetics

Thanks to a better knowledge of the genetic causes of many diseases and an improvement in genetic testing techniques, genetics has gained an important role in the multidisciplinary approach to diagnosis and management of congenital heart disease and aortic pathology. With the introduction of strategies for precision medicine, it is expected that this will only increase further in the future. Because basic knowledge of the indications, the opportunities as well as the limitations of genetic testing is essential for correct application in clinical practice, this consensus document aims to give guidance to care-providers involved in the follow-up of adults with congenital heart defects and/or with hereditary aortic disease. This paper is the result of a collaboration between the ESC Working Group of Grown-Up Congenital Heart Disease, the ESC Working Group on Aorta and Peripheral Vascular Disease and the European Society of Human Genetics. Throughout the document, the importance of correct counseling in the process of genetic testing is emphasized, indications and timing for genetic studies are discussed as well as the technical modalities of genetic testing. Finally, the most important genetic diseases in adult congenital heart disease and aortic pathology are also discussed.

The Past, Present, and Future of Preimplantation Genetic Testing

Preimplantation genetic testing (PGT) of oocytes and embryos is the earliest form of prenatal testing. PGT requires in vitro fertilization for embryo creation. In the past 25 years, the use of PGT has increased dramatically. The indications of PGT include identification of embryos harboring single-gene disorders, chromosomal structural abnormalities, chromosomal numeric abnormalities, and mitochondrial disorders; gender selection; and identifying unaffected, HLA-matched embryos to permit the creation of a savior sibling. PGT is not without risks, limitations, or ethical controversies. This review discusses the techniques and clinical applications of different forms of PGT and the debate surrounding its associated uncertainty and expanded use.

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.

Treatment of infertility in women with pituitary tumors

Due to the pituitary's critical position, a pituitary tumor may disrupt gonadal function, either by its expanding size or the inappropriate secretion of hormones. Menstrual cycles may be disrupted even without frank hypogonadism, particularly in the case of hormone-secreting adenomas. Despite optimal medical and surgical management of pituitary tumors, ovulation-induction therapy with gonadotropins is often required to restore fertility in these women. This article will provide an overview of the therapeutic options available for women with infertility resulting from pituitary tumors. Treatment strategies including dopamine agonists, gonadotropins and the role of assisted reproductive technologies will be discussed. Unique pregnancy considerations in the female patient with hypopituitarism will also be addressed.

The evolving role of genetics in reproductive medicine

As medicine has evolved over the last century, medical genetics has grown from nonexistence to one of the most visible aspects of how we understand and treat disease. This increased role of genetics within medicine will only increase in the coming years, and its role in reproductive medicine will be significant. Genetics has emerged as a primary focus of research with translational applications within reproductive medicine. The aim of this article is to outline the applications of genetics currently available, and how these technologies can provide a positive impact on patient care.

Molecular genetic testing and the future of clinical genomics

Genomic technologies are reaching the point of being able to detect genetic variation in patients at high accuracy and reduced cost, offering the promise of fundamentally altering medicine. Still, although scientists and policy advisers grapple with how to interpret and how to handle the onslaught and ambiguity of genome-wide data, established and well-validated molecular technologies continue to have an important role, especially in regions of the world that have more limited access to next-generation sequencing capabilities. Here we review the range of methods currently available in a clinical setting as well as emerging approaches in clinical molecular diagnostics. In parallel, we outline implementation challenges that will be necessary to address to ensure the future of genetic medicine.

Preimplantation genetic screening: a practical guide

The past several decades have seen tremendous advances in the field of medical genetics. The application of genetic technologies to the field of reproductive medicine has ushered in a new era of medicine that is likely to greatly expand in the coming years. Concurrent with an in vitro fertilization (IVF) cycle, it is now possible to obtain a cellular biopsy from a developing embryo and genetically evaluate this sample with increasing sophistication and detail. Preimplantation genetic screening (PGS) is the practice of determining the presence of aneuploidy (either too many or too few chromosomes) in a developing embryo. However, how and in whom PGS should be offered is a topic of much debate.

PGS-FISH in reproductive medicine and perspective directions for improvement: a systematic review

INTRODUCTION

Embryo selection can be carried out via morphological criteria or by using genetic studies based on Preimplantation Genetic Screening. In the present study, we evaluate the clinical validity of Preimplantation Genetic Screening with fluorescence in situ hybridization (PGS-FISH) compared with morphological embryo criteria.

MATERIAL AND METHODS

A systematic review was made of the bibliography, with the following goals: firstly, to determine the prevalence of embryo chromosome alteration in clinical situations in which the PGS-FISH technique has been used; secondly, to calculate the statistics of diagnostic efficiency (negative Likelihood Ratio), using 2 × 2 tables, derived from PGS-FISH. The results obtained were compared with those obtained from embryo morphology. We calculated the probability of transferring at least one chromosome-normal embryo when it was selected using either morphological criteria or PGS-FISH, and considered what diagnostic performance should be expected of an embryo selection test with respect to achieving greater clinical validity than that obtained from embryo morphology.

RESULTS

After an embryo morphology selection that produced a negative result (normal morphology), the likelihood of embryo aneuploidies was found to range from a pre-test value of 65% (prevalence of embryo chromosome alteration registered in all the study groups) to a post-test value of 55% (Confidence interval: 50-61), while after PGS-FISH with a negative result (euploid), the post-test probability was 42% (Confidence interval: 35-49) (p < 0.05). The probability of transferring at least one euploid embryo was the same whether 3 embryos were selected according to morphological criteria or whether 2, selected by PGS-FISH, were transferred. Any embryo selection test, if it is to provide greater clinical validity than embryo morphology, must present a LR-value of 0.40 (Confidence interval: 0.32-0.51) in single embryo transfer, and 0.06 (CI: 0.05-0.07) in double embryo transfer.

DISCUSSION

With currently available technology, and taking into account the number of embryos to be transferred, the clinical validity of PGS-FISH, although superior to that of morphological criteria, does not appear to be clinically relevant.

Preimplantation genetic testing: indications and controversies

In the last two decades, the use of preimplantation genetic testing has increased dramatically. This testing is used for identifying singlegene disorders, chromosomal abnormalities, mitochondrial disorders, gender selection in non-mendelian disorders with unequal gender distribution, aneuploidy screening, and other preconceptually identified genetic abnormalities in prospective parents. Genetic testing strategies and diagnostic accuracy continues to improve, but not without risks or controversies. In this review the authors discuss the techniques and clinical application of preimplantation genetic diagnosis, and the debate surrounding its associated uncertainty and expanded use.

Canadian Cardiovascular Society 2009 Consensus Conference on the management of adults with congenital heart disease: introduction

With advances in pediatric cardiology and cardiac surgery, the population of adults with congenital heart disease (CHD) has increased. In the current era, there are more adults with CHD than children. This population has many unique issues and needs. Since the 2001 Canadian Cardiovascular Society consensus conference report on the management of adults with CHD, there have been significant advances in the field of adult CHD. Therefore, new clinical guidelines have been written by Canadian adult CHD physicians in collaboration with an international panel of experts in the field. The present introductory section is a summary of the epidemiology and scope of adult CHD in Canada, the structure of the Canadian health care system and adult congenital cardiac health services in Canada. The recommendations for antibiotic prophylaxis and genetic evaluation in this population are included. The complete document consists of four manuscripts, which are published online in the present issue of The Canadian Journal of Cardiology, including sections on genetics, outcomes, diagnostic workups, surgical and interventional options, treatment of arrhythmias, assessment of pregnancy and contraception risks, and follow-up recommendations. The complete document and references can also be found at www.ccs.ca or www.cachnet.org.

Making the blastocyst: lessons from the mouse

Mammalian preimplantation development, which is the period extending from fertilization to implantation, results in the formation of a blastocyst with three distinct cell lineages. Only one of these lineages, the epiblast, contributes to the embryo itself, while the other two lineages, the trophectoderm and the primitive endoderm, become extra-embryonic tissues. Significant gains have been made in our understanding of the major events of mouse preimplantation development, and recent discoveries have shed new light on the establishment of the three blastocyst lineages. What is less clear, however, is how closely human preimplantation development mimics that in the mouse. A greater understanding of the similarities and differences between mouse and human preimplantation development has implications for improving assisted reproductive technologies and for deriving human embryonic stem cells.

Reproductive oocyte/embryo genetic analysis: comparison between fluorescence in-situ hybridization and comparative genomic hybridization

Multiple displacement amplification (MDA) renders an increased quantity of genomic DNA available for comparative genomic hybridization (CGH), enabling it to be used to identify genomic imbalances in human blastomeres. The karyotypic lineage of 57 blastocysts derived from 11 ovum donors following ovarian stimulation was examined. CGH was performed on all first polar bodies, and linearly on corresponding second polar bodies and blastomeres. A diploid karyotype was propagated from the prefertilized oocyte to the embryo in 25 (44%) sets of analyses. In 32/57 sets (56%), aneuploidy was detected in the post-fertilized zygotes/embryos and in nine (28%) of such cases the aneuploidy was 'chaotic' (> or =3 chromosomes). In 4/57 cases (7%) mitotic aneuploidy was observed. CGH and fluorescence in-situ hybridization (FISH) were concurrently performed on two blastomeres removed from each of 44 embryos obtained from four patients. In 43 (98%) of these embryos there was a direct karyotypic correlation between nine-probe commercial FISH and CGH. CGH identified > or =15% more chromosomal abnormalities than through FISH alone. The linear propagation using MDA-CGH, of the same karyotypic abnormalities that affected the oocyte of origin, in the corresponding embryos, coupled with the fact that CGH confirmed the aneuploidies identified through FISH, validates the accuracy and reliability of CGH technology.

The role of the endometrium and embryo in human implantation

Despite many advances in assisted reproductive technologies (ART), implantation rates are still low. The process of implantation requires a reciprocal interaction between blastocyst and endometrium, culminating in a small window of opportunity during which implantation can occur. This interaction involves the embryo, with its inherent molecular programme of cell growth and differentiation, and the temporal differentiation of endometrial cells to attain uterine receptivity. Implantation itself is governed by an array of endocrine, paracrine and autocrine modulators, of embryonic and maternal origin. Implantation failure is thought to occur as a consequence of impairment of embryo developmental potential and/or impairment of uterine receptivity and the embryo-uterine dialogue. Therefore a better comprehension of implantation, and the relative importance of the factors involved, is warranted. New techniques for monitoring changes in the endometrium and/or the embryo at the level of gene regulation and protein expression may lead to the identification of better markers for implantation. Moreover, the use of predictive sets of markers may prove to be more reliable than a single marker. Continuing refinements to ART protocols, such as optimizing ovarian stimulation regimens, the timing of human chorionic gonadotrophin injection, or the timing of embryo transfer, should help to increase implantation rates further.

Genetic basis for congenital heart defects: current knowledge: a scientific statement from the American Heart Association Congenital Cardiac Defects Committee, Council on Cardiovascular Disease in the Young: endorsed by the American Academy of Pediatrics

The intent of this review is to provide the clinician with a summary of what is currently known about the contribution of genetics to the origin of congenital heart disease. Techniques are discussed to evaluate children with heart disease for genetic alterations. Many of these techniques are now available on a clinical basis. Information on the genetic and clinical evaluation of children with cardiac disease is presented, and several tables have been constructed to aid the clinician in the assessment of children with different types of heart disease. Genetic algorithms for cardiac defects have been constructed and are available in an appendix. It is anticipated that this summary will update a wide range of medical personnel, including pediatric cardiologists and pediatricians, adult cardiologists, internists, obstetricians, nurses, and thoracic surgeons, about the genetic aspects of congenital heart disease and will encourage an interdisciplinary approach to the child and adult with congenital heart disease.

Peroxisome biogenesis disorders

Defects in PEX genes impair peroxisome assembly and multiple metabolic pathways confined to this organelle, thus providing the biochemical and molecular bases of the peroxisome biogenesis disorders (PBD). PBD are divided into two types--Zellweger syndrome spectrum (ZSS) and rhizomelic chondrodysplasia punctata (RCDP). Biochemical studies performed in blood and urine are used to screen for the PBD. DNA testing is possible for all of the disorders, but is more challenging for the ZSS since 12 PEX genes are known to be associated with this spectrum of PBD. In contrast, PBD-RCDP is associated with defects in the PEX7 gene alone. Studies of the cellular and molecular defects in PBD patients have contributed significantly to our understanding of the role of each PEX gene in peroxisome assembly.

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.