Hemizygous deletion of WT1 in T-ALL. (A) Chromosome 11 ideogram and copy number (top) and LOH analysis (bottom) of paired diagnostic (squares), relapsed (triangles), and remission (circles) T-ALL samples. Flanking SNPs and genes included in these alterations are indicated. Roman numbers identify individual patients. (B) FISH and mutation analysis of WT1 in diagnostic sample V. (C) FISH and mutation analysis of WT1 in diagnostic sample I. A chromosome 11 centromeric probe is shown in blue. An intact WT1 locus is marked by an orange signal from a WT1 BAC clone labeled in green and BAC clones telomeric and centromeric to WT1 labeled in red. Arrows indicate nuclei with hemizygous deletions of WT1. DNA sequence chromatograms focus in the WT1 exon 7 sequences containing frameshift mutations of WT1 in each of these samples. Note that, although areas of LOH are marked across diagnostic, remission, and relapsed samples, this corresponds to genetic lesions present in diagnostic and/or relapsed samples compared with the corresponding normal remission DNA.