Preimplantation genetic diagnosis: an overview and recent advances

Protecting Future Generations From Hereditary Genetic Disorders Using Preimplantation Genetic Diagnosis: A Narrative Review Article

Preimplantation genetic diagnosis (PGD) is provided by majority of reproductive clinics in the United States (US), and PGD is used in many in vitro fertilization (IVF) procedures every year. PGD is extensively used to screen for certain genetic abnormalities and aneuploidy in individuals undergoing IVF. Genetic disorders are very prevalent in Saudi Arabia. The high prevalence of consanguinity in the population explains, to a great extent, the incidence of genetic disorders being relatively higher in the Kingdom of Saudi Arabia (KSA) compared to many other countries. Estimates range from 6% to 10% among all live births, and at least one study estimated that up to 30% of the population couldbe affected by a genetic disorder at any time in their lifetime. Therefore, a preventive measure such as PGD is useful for detecting genetic disorders before implantation. In KSA, genetic disorders are prevalent with a high psychological and financial burden. A diagnostic procedure like PGD is useful for detecting genetic disorders. It is used to analyze embryos under the IVF cycle. Then, a biopsy is taken from the embryos and analyzed using techniques such as polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH). Only healthy embryos are transferred to the uterus, thus eliminating the need for a parental diagnostic test that comes with substantial risk to the mother and the fetus. PGD is used for the detection of genetic abnormalities such as sex-linked diseases and chromosomal abnormalities, helping parents with genetic disorders to conceive a healthy child. Some of the limitations of PGD are its unavailability and the high cost, which limit the access for parents of low socioeconomic status. It creates many decision-making problems for the facilities and parents. Our objectives include giving an overview of PGD history, demonstrating indications for this procedure, explaining its techniques, and discussing the ethical issues surrounding it. PGD offers improved IVF results and reduced genetic disorder prevalence but also has disadvantages like high costs, limited access, and ethical concerns.

Pre-implantation Genetic Diagnosis: The Road Forward in Canada

The use of pre-implantation genetic diagnosis (PGD) is increasing as the list of indications it can test for constantly expands. This raises new challenges for clinicians and prospective parents regarding possible uses and calls for guidance. Policy approaches towards PGD vary greatly worldwide. The 2004 Canadian Assisted Human Reproduction Act does not provide guidance, except for prohibiting non-medical sex selection. Criminal legislation is an unsuitable policy instrument to regulate human genetics and reproductive medicine. We call for professional societies to issue guidelines regarding the uses of PGD that would establish the standard of care and legal norms. Such guidelines should be based on a patient-centered approach and respect individual autonomy in reproductive decision-making. Canadian approaches to PGD should also consider issues related to equity of access. Moreover, since PGD often raises concerns about eugenic uses, guidelines should also consider its societal impact and its implementation should be accompanied by policies that maintain or increase social support for people with disabilities. Finally, public engagement could provide an evidence-base regarding Canadian societal values and concerns that should guide regulatory reform, for example, the regulation of non-medical sex selection through PGD.

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.