Translocation trisomy dup(21q) and free trisomy 21 can be distinguished by interphase-FISH.
The possibility of distinguishing in routine diagnostics translocation trisomy dup(21q) from disomy 21 as well as from free trisomy 21 using interphase fluorescence in situ hybridization (FISH) with a single copy probe (LSI 21) localized on chromosome 21q22.13-q22.2 is described. In free trisomy 21 and translocation trisomy dup(21q) 94%-98% of the nuclei exhibit 3 specific signals, while in disomy 21 only up to 6% of them have 3 false positive signals. Furthermore, reliable differentiation between free and translocation trisomy dup(21q) can be achieved by evaluating the percentage of nuclei with one single and two co-localized chromosome 21q22.13-q22.2 specific signals in 50-100 interphase nuclei. While in translocation trisomy 75+/-4.3% are co-localized due to a chromosomal rearrangement, in free trisomy 21 only 40+/-2.83% of the nuclei have two co-localized signals by chance. No differences in interphase signal distribution could be detected in two cases with a dicentric chromosome dup(21q) compared to one case with a monocentric one, a comparison not previously carried out. In addition, the single copy probe LSI 21 was compared with the alphoid probe D13Z1/D21Z1 which was found to be unsuitable for such assays due to polymorphisms in the á satellite regions of chromosome 21.
Liehr
T
T
Institut fur Humangenetik und Anthropologie, D-07740 Jena, Germany.
Starke
H
H
Beensen
V
V
Kähler
C
C
Harbich
M
M
Brude
E
E
Ziegler
M
M
Claussen
U
U
D000653:Amniotic Fluid / Q000166:cytology; D002467:Cell Nucleus / Q000378:metabolism; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D015342:DNA Probes; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007399:Interphase; D011247:Pregnancy; D011296:Prenatal Diagnosis; D014178:Translocation, Genetic; D014314:Trisomy / Q000175:diagnosis / Q000235:genetics*
D015342:DNA Probes