Preimplantation genetic diagnosis for myotonic dystrophy type 1: detection of crossover between the gene and the linked marker APOC2.
OBJECTIVE
To report two cases of preimplantation genetic diagnosis (PGD) for myotonic dystrophy type I (DM1) where cross-over between the DMPK locus and a linked polymorphic marker APOC2 was detected.


METHODS
Embryos from in vitro fertilisation (IVF) were biopsied at day 3 of development and single blastomeres collected. Diagnosis was performed by duplex or triplex fluorescent-polymerase chain reaction (F-PCR) to amplify DMPK and APOC2 loci, or DMPK with APOC2 and D19S112 polymorphic markers.


RESULTS
A total of 22 oocytes were retrieved from the two patients, 20 were inseminated of which 15 fertilized (75%) and were suitable for biopsy on day 3. A diagnosis was obtained for 12 embryos (80%) and was confirmed in all un-transferred embryos. Crossover between DM1 and APOC2 was detected in two embryos from the two different couples. Transfer of two embryos took place in both cases resulting in two pregnancies. Each couple have had a healthy baby.


CONCLUSIONS
The above cases highlight the importance of using more than one linked polymorphic marker in PGD-PCR protocols and emphasize the danger of using APOC2 as the sole marker to identify the DM1 mutation.
Kakourou
Georgia
G
UCL Centre for Preimplantation Genetic Diagnosis, Department of Obstetrics and Gynaecology, University College London, UK.
Dhanjal
Seema
S
Daphnis
Danny
D
Doshi
Alpesh
A
Nuttall
Sarah
S
Gotts
Sarah
S
Serhal
Paul
P
Delhanty
Joy
J
Harper
Joyce
J
SenGupta
Sioban
S
D000328:Adult; D053304:Apolipoprotein C-II / Q000235:genetics*; D001706:Biopsy; D003434:Crossing Over, Genetic / Q000235:genetics*; D005260:Female; D005307:Fertilization in Vitro; D008040:Genetic Linkage; D005819:Genetic Markers / Q000235:genetics; D005820:Genetic Testing; D006801:Humans; D008297:Male; D009223:Myotonic Dystrophy / Q000175:diagnosis* / Q000235:genetics; D065636:Myotonin-Protein Kinase; D009865:Oocytes / Q000737:chemistry / Q000473:pathology; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D019836:Preimplantation Diagnosis / Q000379:methods*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*
D053304:Apolipoprotein C-II; C585517:DMPK protein, human; D005819:Genetic Markers; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases