Preimplantation genetic diagnosis for single gene disorders: experience with five single gene disorders.
We report our experience of 14 preimplantation genetic diagnosis (PGD) cycles in eight couples carrying five different single gene disorders, during the last 18 months. Diagnoses were performed for myotonic dystrophy (DM), cystic fibrosis (CF) [Delta F508 and exon 4 (621+1 G>T)], fragile X and CF simultaneously, and two disorders for which PGD had not been previously attempted, namely neurofibromatosis type 2 (NF2) and Crouzon syndrome. Diagnoses for single gene disorders were carried out on ideally two blastomeres biopsied from Day 3 embryos. A highly polymorphic marker was included in each diagnosis to control against contamination. For the dominant disorders, where possible, linked polymorphisms provided an additional means of determining the genotype of the embryo hence reducing the risk of misdiagnosis due to allele dropout (ADO). Multiplex fluorescent polymerase chain reaction (F-PCR) was used in all cases, followed by fragment analysis and/or single-stranded conformation polymorphism (SSCP) for genotyping. Embryo transfer was performed in 13 cycles resulting in one biochemical pregnancy for CF, three normal deliveries (a twin and a singleton) and one early miscarriage for DM and a singleton for Crouzon syndrome. In each case the untransferred embryos were used to confirm the diagnoses performed on the biopsied cells. The results were concordant in all cases. The inclusion of a polymorphic marker allowed the detection of extraneous DNA contamination in two cells from one case. Knowing the genotype of the contaminating DNA allowed its origin to be traced. All five pregnancies were obtained from embryos in which two blastomeres were biopsied for the diagnosis. Our data demonstrate the successful strategy of using multiplex PCR to simultaneously amplify the mutation site and a polymorphic locus, fluorescent PCR technology to achieve greater sensitivity, and two-cell biopsy to increase the efficiency and success of diagnoses.
Department of Obstetrics and Gynaecology, University College London, London, UK. joyce.harper@ucl.ac.uk
Joyce C
JC
Harper
Dagan
D
Wells
Wirawit
W
Piyamongkol
Patrick
P
Abou-Sleiman
Angela
A
Apessos
Antonis
A
Ioulianos
Mary
M
Davis
Alpesh
A
Doshi
Paul
P
Serhal
Massimo
M
Ranieri
Charles
C
Rodeck
Joy D A
JD
Delhanty
D000328:Adult; D000483:Alleles; D003394:Craniofacial Dysostosis / Q000175:diagnosis* / Q000235:genetics; D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000235:genetics; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics; D005091:Exons; D005260:Female; D005307:Fertilization in Vitro; D005600:Fragile X Syndrome / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D008297:Male; D009223:Myotonic Dystrophy / Q000175:diagnosis* / Q000235:genetics; D016518:Neurofibromatosis 2 / Q000175:diagnosis* / Q000235:genetics; D016133:Polymerase Chain Reaction; D019836:Preimplantation Diagnosis
C505032:CFTR protein, human; C093349:cystic fibrosis transmembrane conductance regulator delta F508; D019005:Cystic Fibrosis Transmembrane Conductance Regulator