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  • Cited by 12
  • 2nd edition
  • Edited by Joyce Harper, University College London
Publisher:
Cambridge University Press
Online publication date:
November 2009
Print publication year:
2009
Online ISBN:
9780511581571

Book description

Preimplantation genetic diagnosis (PGD) is a key technique in modern reproductive medicine. Originally developed to help couples who were at risk of transmitting single-gene genetic abnormalities to their children, the development of the FISH technique broadened chromosome analysis to include detection of more complex inherited abnormalities. The last decade has seen the development of aneuploidy screening (PGS) for infertile couples, using the same techniques as PGD but screening for as many chromosomes as possible. PGD has always been a controversial procedure and embryo manipulation and selection is still illegal in some countries. The second edition of this leading textbook describes all aspects of PGD, with chapters written by key international experts in the field. A must for anyone interested in learning more about PGD, it will be of interest to everyone working in the fields of IVF, genetic diagnosis, genetic counselling, and prenatal diagnosis - including clinicians, embryologists, nurses, and clinical scientists.

Reviews

'… large educational value … enjoyable to read and easy to understand, also if you are far from being an expert in the field.'

Source: Acta Obstetricia et Gynecologica

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Contents

  • Chapter 7 - Preimplantation genetics
    pp 137-150
  • View abstract

    Summary

    In vitro fertilization (IVF) was initially developed to treat patients with damaged Fallopian tubes. IVF treatment has since been extended far beyond tubal infertility to treat a whole host of indications, including unexplained infertility, endometriosis, and male infertility. Infertility treatments include timed intercourse, ovulation induction, intrauterine insemination (IUI), gamete intrafallopian transfer (GIFT), zygote intrafallopian transfer (ZIFT), IVF, and intracytoplasmic sperm injection (ICSI). Standard stimulation protocols require pituitary desensitization with a GnRH agonist, and this strategy has become almost a universal practise in assisted conception clinics with the induced hypogonadotropic hypogonadism enabling almost complete control over follicular development. The presence of endometrial polyps, submucous fibroids, and intrauterine adhesions may be associated with reduction in pregnancy rates and increase in risk of miscarriage with IVF. Cryopreservation of supernumerary good-quality embryos is vital to optimize pregnancy rates per cycle started without the need to superovulate the patient again.
  • Section 2 - Procedures used in preimplantation genetic diagnosis
    pp 151-258
  • View abstract

    Summary

    Inherited disease may be caused at the level of the gene and the chromosome. In principle single gene mutations can lead to genetic diseases which may be distinguished on the basis of five simple modes of inheritance: autosomal dominant, autosomal recessive, X-linked recessive, X-linked dominant, and Y-linked. Myotonic dystrophy, DM1, also known as Steinert disease, is a progressive muscular dystrophy caused by the expansion in number of copies of a CTG repeat in the 3ʹ-untranslated part of the DM1 kinase gene on chromosome 19. Huntington disease is a progressive neuropsychiatric, late-onset disorder. Fragile X syndrome is a form of X-linked mental retardation caused by unstable expansion of a CGG repeat in the 5ʹ untranslated region of the FMR1 gene. Ring chromosomes are formed when genetic material is lost from both ends of a chromosome, creating an unstable situation which is resolved by the fusion of the broken ends.
  • Chapter 9 - Polar body biopsy
    pp 166-174
  • View abstract

    Summary

    This chapter deals with the issues that are discussed at an initial preimplantation genetic diagnosis (PGD) consultation, and describes the relevance and benefits of genetic counseling at this stage in the referral process. Chromosomal rearrangements initially believed to carry reproductive risk in the form of miscarriage or physical or mental disability, where family members may have considered prenatal testing, may be reevaluated and thus now represent normal variants without reproductive risk. The reproductive options for couples at risk of genetic disease will usually have been addressed by the genetic clinician prior to the referral for PGD. For many patients the time between taking a positive pregnancy test and undertaking prenatal diagnosis (PND) is a huge emotional burden that they know may end unsuccessfully. Many centers offering PGD are now able to do so for genetic disorders that may not affect an individual until adulthood, for example Huntington disease.
  • Chapter 10 - Cleavage-stage embryo biopsy
    pp 175-185
  • View abstract

    Summary

    This chapter outlines the principles and techniques of prenatal diagnosis and discusses some potential future developments in prenatal diagnosis. Prenatal diagnosis of congenital birth defects or genetic disorders is based on screening a low-risk population. First-trimester sonographic assessment of fetal anatomy has become an important component of prenatal diagnosis. A number of different views of the fetus are available with 3D ultrasound, such as surface rendering to display the skin surface, transparency mode, and maximal intensity mode. The introduction of ultrafast imaging methods such as echo planar imaging and single shot fast spin echo techniques allow the acquisition of single, high-resolution images in less than one second and have made magnetic resonance imaging (MRI) examination of the fetus a real possibility. Invasive tests in pregnancy are used to obtain fetal cells, fluids, or tissues that are used for prenatal diagnosis of aneuploidy, fetal congenital disease, and fetal infection.
  • Chapter 11 - Blastocyst biopsy
    pp 186-192
  • View abstract

    Summary

    This chapter determines embryo viability in the human. Male and female gametes which unite to form each embryo are derived from a unique population of primordial cells that are designated to become the gametes: they develop into highly specialized gametes by the processes of spermatogenesis in the male and oogenesis in the female. Fertilization is a specialized example of cell-to-cell interaction. After fertilization the zygote divides by mitosis into a number of smaller cells called blastomeres. Cleavage may be considered a mitotic process, as found in adult somatic tissues, there is one important difference: in adult tissue the daughter cells grow following each division and are not able to divide again until they have achieved the original size of the parent cell. The metabolic requirements of the preimplantation embryo vary through the preimplantation period, and clear differences in metabolism are seen between pre- and post-compaction stages.
  • Chapter 12 - Preimplantation genetic diagnosis for chromosome rearrangements
    pp 193-202
  • View abstract

    Summary

    A number of research and clinical studies have confirmed high frequency of cytogenetic abnormalities in human oocytes and embryos. Chromosomal imbalance in oocytes can result from loss or gain of individual chromatids or whole chromosomes. The underlying causes remain to be fully elucidated, but important modifying factors include the number and location of chiasmata and maternal age. Aneuploidy is a major cause of congenital abnormalities, mental retardation, and miscarriage. However, most of the chromosome abnormalities detected in human embryos are likely to be lethal at very early embryonic stages, and are probably incompatible with the formation of a clinical pregnancy. Many fertility clinics now screen the embryos produced during in vitro fertilization (IVF) cycle in order to identify those that are chromosomally normal. Screening the oocytes/embryos from these patients for aneuploidy using PGS may be particularly beneficial in terms of IVF outcome.
  • Chapter 14 - Preimplantation genetic diagnosis for sex-linked diseases and sex selection for non-medical reasons
    pp 230-236
  • View abstract

    Summary

    Laser-assisted polar body biopsy is best accomplished when the oocyte is affixed to the holding capillary with the first polar body at 12 O'clock position and the second polar body located right of the first one but in the same focal plane. In contrast to embryonic blastomeres, polar bodies are rather small and do not require any special pretreatment like hypo-osmotic swelling or pronase digestion. The size and position of openings drilled in the zona pellucida (ZP) can influence further embryonic development and in particular the mode of hatching at the blastocyst stage. The presence of a cytoplasmic bridge between the first as well as the second polar body and the oocyte can impose during biopsy. A frequent problem in analysis of the first polar body is high degree of fragmentation observed in human first polar bodies.
  • Chapter 15 - Preimplantation genetic diagnosis for monogenic disorders: multiplex PCR and whole-genome amplification for gene analysis at the single cell level
    pp 237-246
  • View abstract

    Summary

    The European Society of Human Reproduction and Embryology (ESHRE) Preimplantation Genetic Diagnosis (PGD) Consortium data collection shows that the most widely used biopsy procedure is indeed cleavage-stage biopsy. Cleavage-stage biopsy of human preimplantation embryos always involves two steps: opening of the zona pellucida (ZP) and subsequent removal of cellular material. The opening of the ZP by laser technology has been introduced in clinical embryo biopsy practice more recently. Compaction in the mammalian preimplantation embryo is an essential event that leads to the formation of the trophectoderm, the inner cell mass and the blastocele. Embryos for PGD by means of PCR are ideally obtained by micro-injection of a single sperm cell in order to avoid contamination with naked sperm DNA. Embryo post- biopsy development can be evaluated on a day, where doubling of cells and/or signs of compaction represents good evolution.
  • Chapter 16 - Quality control and quality assurance in preimplantation genetic diagnosis
    pp 247-258
  • View abstract

    Summary

    This chapter discusses current methodology and the advantages and limitations of blastocyst biopsy. The first phase of blastocyst biopsy involves making a hole in the zona pellucida (ZP). The dissection of the ZP may be performed mechanically, by the application of acid Tyrodes solution, or through the use of laser technology. The cryopreservation of biopsied embryos continues to be one of the weak points of preimplantation genetic diagnosis (PGD). The results published by most groups show that embryos with an opening in the ZP are more sensitive to the freezing process, which is reflected in reduced survival and developmental rates among frozen-thawed biopsied embryos. Vitrification as an alternative to classical freezing techniques is adopted as part of numerous in-vitro fertilization (IVF) programs due to its simplicity and, above all, the excellent results obtained not only in oocytes but also in early embryos and blastocysts.
  • Section 3 - Ethics and the future
    pp 259-285
  • View abstract

    Summary

    Couples, where one partner carries a balanced chromosome rearrangement or other structural chromosome abnormality, are at the risk of genetically unbalanced conceptions, which may result in failure to implant, early or late miscarriage, or liveborn children with physical and mental disability. Chromosome rearrangements include Robertsonian and reciprocal translocations, peri- and para-centric inversions, inter- and intrachromosomal insertions, deletions, duplications, and complex chromosome rearrangements (CCRs). Balanced reciprocal translocations, which are typically an exchange of two terminal segments from different chromosomes, occur in approximately one in 500 live births, and are usually associated with a normal phenotype. Robertsonian translocations occur with a prevalence of one in 1000 in the general population. Carriers of balanced pericentric inversions are at risk of pregnancies with imbalance for the noninverted segments. Imbalance for the noninverted segments may be ascertained by using subtelomeric probes for the relevant segments.
  • Chapter 18: - Preimplantation genetic diagnosis: the future
    pp 274-285
  • View abstract

    Summary

    The incidence of chromosomal abnormalities in cleavage-stage embryos produced in vitro, 50-70 percent depending on maternal age, is considerably higher than that of spontaneous abortions, indicating that a sizeable percentage of chromosomally abnormal embryos are eliminated before any prenatal diagnosis. In most in vitro fertilization (IVF) laboratories one of the powerful tools to improve results is embryo selection, based on morphological and developmental characteristics. FISH is currently the best method to analyze polar bodies and blastomeres since the former have poor quality metaphases and in the latter metaphases are produced in low rates even after culture. Mosaicism rates vary in the literature. Some of the differences between centers are attributed to the population; others to hormonal stimulation and the general quality of embryos produced in those centers. Recurrent miscarriage (RM) in patients with normal karyotype is defined as three or more consecutive spontaneous abortions of less than 20-28 weeks gestation.

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