Demonstration of partial trisomy 3 in the PBMCs of the index case.

(A) CGH. Partial profile of chromosome 3 showing the region of duplication involving the long(q) arm. Chromosomal regions were considered overrepresented when the corresponding green-to-red ratio exceeded 1:18 and underrepresented when the ratio was below 0:83. Thresholds were fixed on profiles obtained from hybridization of 2 differently labeled normal DNAs extracted from healthy donors. Telomeric and centromeric regions as well as heterochromatic regions of chromosome 1, 9, 16, and Y were excluded from analysis, because of possibly false-positive results. Results were confirmed by means of a 99% confidence interval, with 1% error probability. (B) Interphase FISH with probe for centromeric sequences of chromosome 3 showing only disomic nuclei. Signals were evaluated on 600 interphase cells, of which 2.6% showed 1 spot; 97.1%, 2 spots; and 0.3%, 3 spots. (C) Interphase FISH with the locus-specific probe for MLF1 gene (3q25) showing 3 spots in 3 of 4 nuclei. Signals were evaluated in 100 interphase cells, of which 20% showed 2 spots and 80% showed 3 spots.