Post-zygotic origin of isochromosome 12p.
OBJECTIVE
Advance knowledge about the mechanism of isochromosome formation.


METHODS
Echographic examination of the foetus. G- and/or T-banded chromosome and FISH analysis using chromosome 12p subtelomeric probes on short- and long-term CVS cultures, amniocytes and foetal fibroblasts. Polymorphic CA repeat analysis on DNA from the foetus and both parents.


RESULTS
Short-term CVS cultures showed a 46,XX karyotype, whilst long-term CVS cultures showed a 47,XX,+12 karyotype. FISH on amniocytes indicated 2, 3 and 4 signals. Foetal fibroblasts showed both 47,XX,+12 and 47,XX,+i(12)(p10) karyotypes. DNA analysis revealed the isochromosome to be paternal in origin, whilst the other two foetal chromosomes 12 were maternal, part iso- and part heterodisomy.


CONCLUSIONS
The cytogenetic and DNA constitution of the foetus indicated the isochromosome 12p to be of paternal origin, and implied post-zygotic formation of the isochromosome 12p in the Pallister-Killian syndrome.
de Ravel
Thomy J L
TJ
Centre for Human Genetics, UZ Gasthuisberg, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium. Thomy.deRavel@uz.kuleuven.ac.be
Keymolen
Kathelijn
K
van Assche
Elvire
E
Wittevronghel
Ingrid
I
Moerman
Philippe
P
Salden
Ivo
I
Matthijs
Gert
G
Fryns
Jean-Pierre
JP
Vermeesch
Joris R
JR
D000328:Adult; D000483:Alleles; D000653:Amniotic Fluid / Q000166:cytology; D002478:Cells, Cultured; D002824:Chorionic Villi / Q000648:ultrastructure; D002871:Chromosome Banding; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D004247:DNA / Q000032:analysis; D005260:Female; D005347:Fibroblasts; D005865:Gestational Age; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D018404:Isochromosomes / Q000235:genetics*; D007621:Karyotyping; D011247:Pregnancy; D011296:Prenatal Diagnosis; D015053:Zygote
D004247:DNA