Development and successful clinical application of preimplantation genetic haplotyping for Herlitz junctional epidermolysis bullosa.

[junctional epidermolysis bullosa]

Herlitz junctional epidermolysis bullosa (HJEB ) is a severe , life-threatening , autosomal recessive blistering skin disease for which no cure is currently available . Prenatal diagnosis for couples at risk is feasible through fetal skin biopsy or analysis of DNA extracted from chorionic villi , but these methods can be applied only after pregnancy has been established . An alternative approach , which involves the analysis of single cells from embryos prior to establishment of pregnancy , is preimplantation genetic diagnosis (PGD ). Until now , its clinical uptake has been hindered by lengthy delays in establishing mutation -specific protocols , and by the small amount of template DNA that can be obtained from a single cell . A new method that addresses these problems , preimplantation genetic haplotyping (PGH ), relies on whole genome amplification followed by haplotyping of multiple polymorphic markers using standard DNA-based polymerase chain reaction (PCR ) assays .To design and validate a generic PGH assay for HJEB and to transfer this into clinical practice .We established a multiplex PCR-based PGH assay involving 16 markers within and flanking the LAMB 3 gene (the most frequently mutated gene in HJEB ). The assay was then validated in 10 families with at least one previously affected offspring . After licensing by the Human Fertilisation and Embryology Authority (HFEA ), the new test was used for PGD in a couple at risk of HJEB .T he chromosome 1 LAMB 3 markers within the assay were shown to be of sufficient heterogeneity to have widespread application for preimplantation testing of HJEB . In one couple that were heterozygous carriers of nonsense mutations in LAMB 3 , we used the new assay to identify unaffected embryos in a series of PGD cycles . Pregnancy was established in the third PGD cycle and a healthy , unaffected child was born . DNA analysis of cord blood confirmed the predicted single -cell mutation status of wild-type LAMB 3 alleles .PGH represents a major step forward in widening the scope and availability of preimplantation testing for serious mapped single -gene disorders . We have established a generic test that is suitable for the majority of couples at risk of HJEB .

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Diseases presenting "specific protocols" symptom

classical phenylketonuria

junctional epidermolysis bullosa

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