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EA 7402 University of Montpellier
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Update: 19-12-2016

Preimplantation Genetic Diagnosis for monogenic disorders

       The intented goal of Preimplantation Genetic Diagnosis (PGD) is to diagnose a specific genetic disease on single cells from embryos obtained through an in vitro fertilization (IVF) procedure, by selecting and transferring to the woman's uterus only embryos found to be unaffected, before a clinical pregnancy has been established. Genetic diagnosis is performed on one or two blastomeres biopsied from 3 days-old embryos, then embryos free of the disease under investigation are transferred to the mother on day 4 or 5.
For some couples at high risk of transmitting a genetic disorder to their offspring, PGD is an alternative approach to conventional prenatal diagnosis (PND) as it avoids the emotional burden associated with termination of pregnancy.
Most of couples seeking PGD already have an affected child, have lost affected children due to the genetic condition and wish to avoid further risk, and/or have experienced repeated elective therapeutic abortion of an affected fetus. Until recently, couples at risk who wished to prevent the birth of an affected child could remain childless, opt for a spontaneous pregnancy with prenatal diagnosis and termination of pregnancy if the fetus was shown to be affected, choose gamete donation or adoption.
For all couples requesting PGD, the disease-causing mutation must have been previously identified. According to the french law, only this genetic abnormality as well as linked markers may be studied.
In France, PGD has been allowed by the law dated 29th July 1994, for couples at risk of transmitting a serious genetic disorder to their offspring. PGD may only be performed in four specialized centers, that have been licensed by the Agence de la Biomédecine : Strasbourg and Paris (since 1999), Montpellier (since 2003) and Nantes (since 2013).


DPI principle
PGD cycle

PGD indications

       PGD indications are quite similar to those practiced in prenatal diagnosis, i.e serious hereditary disorders that may result in a therapeutic abortion following prenatal diagnosis of an affected fetus. According to european recommendations, couples requesting information about PND may also be counselled about PGD, limits and errors related to PGD, as well as the possibility to perform PND to confirm PGD results.

      The PGD procedure is applied to monogenic disorders, that are classified into four main categories :

  • Autosomal recessive disorders: the mutant gene is inherited from both unaffected parents; the risk of having an affected child is therefore 25%. Cystic fibrosis, hemoglobin disorders, spinal muscular atrophy are common indications of PGD.
  • Autosomal dominant disorders: the risk of having an affected child is 50% as a mutation in only one of the two gene copies is sufficient to cause disease expression. Examples: myotonic dystrophy, Huntington disease, familial polyposis coli, von Hippel Lindau disease, retinoblastoma…
  • X-linked recessive disorders: the risk of having an affected male embryo is 25%. Examples: Duchenne muscular dystrophy, haemophilia…
  • X-linked dominant disorders: the risk of having an affected child is 50%. Examples: Fragile X syndrome, Alport syndrome…

Risks and pitfalls

      The study of specific DNA sequences in a single blastomere is a substantial challenge as many problems may compromise both the accuracy and reliability of the genetic diagnosis. For the detection of single gene defects, the prevalent method of diagnosis is PCR (polymerase chain reaction) allowing the exponential amplification of short DNA sequences, which are subsequently detected and analysed.
Since the first PCR-based PGD cases, genetic analysis for single gene disorders has evolved considerably. However, major difficulties are still encountered in single cell analysis because of the minute amount of DNA available: DNA contamination of the sample with extraneous non-embryonic DNA, amplification failure, and Allele drop out (ADO), which is defined as the random non-amplification or non-detection of one of the alleles present in a heterozygous sample.
All couples have to be aware of these technical limitations as they may lead to absence of diagnosis or to potential misdiagnosis.

Preclinical work-up

      Before clinical application, extensive preclinical trials have to be performed on several single cells isolated under an inverted microscope (lymphocytes or lymphoblasts), including the development of specific PCR protocols as well as techniques chosen to identify mutations and polymorphic markers. Otherwise, the aim of these preclinical experiments is to evaluate amplification efficiencies and ADO rates for all the DNA sequences to be studied in the procedure. For most of PGD indications, the development, optimization and validation procedures can take several weeks to several months, according to the genes studied and techniques used. Work-up results on single cells are considered satisfactory for clinical application when they fall within the limits set in the ESHRE PGD consortium's guidelines : amplification efficiencies may be above 90% and ADO rates may be lower than 10%. However, single cell amplification efficiencies and ADO rates can vary greatly with different cell types, especially in blastomeres from poor embryo quality that frequently exhibit inconclusive results.

Available PGD indications for monogenic disorders in the CHU of Montpellier

      In France, some PGD indications are only performed in our center (hemolytic disease, aniridia, molybdenum cofactor deficiency, vascular Ehlers-Danlos syndrome, Carvajal syndrome…). For other indications (such as cystic fibrosis and Duchenne muscular dystrophy), we have developed powerful protocols in order to accept in our PGD program most of the couples requesting PGD for these conditions. Finally, for other families, we have set up techniques enabling to distinguish healthy embryos from monosomic embryos (for the chromosome studied). Thus, the embryologist may select for transfer, among a large cohort of unaffected embryos, the embryo(s) displaying the best morphology and kinetics of development. Consequently, the rates of pregnancy are improved.

Other PCR-based PGD protocols are being developed to provide an opportunity for couples to rapidly being accepted in our PGD program, provided that the genetic condition has been previously accepted by the multidisciplinary network licensed for PGD.
List of disorders (Microsoft Excel format)

  • Staff

  • Anne GIRARDET (PhD, MCU-PH CHU Montpellier)

    Aliya ISHMUKHAMETOVA (PhD, PAA CHU Montpellier)

    Stéphanie PLAZA (PhD, Engineer CHU Montpellier)

    Sandie MEREUZE (PhD, Engineer CHU Montpellier)

    Victoria VIART (PhD, Engineer CHU Montpellier)

    Florielle SAGUET (TL CHU Montpellier)

    Garance VERRIERE (TL CHU Montpellier)

  • Keywords: Preimplantation Genetic Diagnosis (PGD), single cell, sperm-typing

  • Access

  • Selected publications
  • Girardet A, Ishmukhametova A, Viart V, Plaza S, Saguet F, Verriere G, Hamamah S, Coupier I, Haquet E, Anahory T, Willems M, Claustres M. Thirteen years' experience of 893 PGD cycles for monogenic disorders in a publicly funded, nationally regulated regional hospital service. Reprod Biomed Online. 2018 Feb;36(2):154-163. PMID: 29203382

    Viart V, Willems M, Ishmukhametova A, Dufernez F, Anahory T, Hamamah S, Schmitt S, Claustres M, Girardet A. Germline mosaicism is a pitfall in PGD for X-linked disorders. Single sperm typing detects very low frequency paternal gonadal mosaicism in a case of recurrent chondrodysplasia punctata misattributed to a maternal origin.Prenat Diagn. 2017 Feb;37(2):201-205. PMID: 27943351

    Girardet A, Viart V, Plaza S, Daina G, De Rycke M, Des Georges M, Fiorentino F, Harton G, Ishmukhametova A, Navarro J, Raynal C, Renwick P, Saguet F, Schwarz M, SenGupta S, Tzetis M, Roux AF, Claustres M. The improvement of the best practice guidelines for preimplantation genetic diagnosis of cystic fibrosis: toward an international consensus. Eur J Hum Genet. 2015 May 27. doi: 10.1038/ejhg.2015.99. [Epub ahead of print] PMID: 26014425

    Girardet A, Ishmukhametova A, Willems M, Coubes C, Hamamah S, Anahory T, Des Georges M, Claustres M. Preimplantation genetic diagnosis for cystic fibrosis: the Montpellier center's 10-year experience. Clin Genet. 2015 Feb;87(2):124-32. doi: 10.1111/cge.12411. Epub 2014 May 20. PMID: 24762087

    Girardet A, Fernandez C, Claustres M. Rapid and powerful decaplex and dodecaplex PGD protocols for Duchenne muscular dystrophy. Reprod Biomed Online. 2009 Dec;19(6):830-7. PMID: 20031025

    Barat-Houari M, Nguyen K, Bernard R, Fernandez C, Vovan C, Bareil C, Khau Van Kien P, Thorel D, Tuffery-Giraud S, Vasseur F, Attarian S, Pouget J, Girardet A, Lévy N, Claustres M. New multiplex PCR-based protocol allowing indirect diagnosis of FSHD on single cells: can PGD be offered despite high risk of recombination? Eur J Hum Genet. 2010 May;18(5):533-8. doi: 10.1038/ejhg.2009.207. Epub 2009 Nov 25. PMID: 19935833