Prader Willi/Angelman and DiGeorge/velocardiofacial syndrome deletions: diagnosis by primed in situ labeling (PRINS).

A recently developed methodology-primed in situ labeling (PRINS)-can be used in place of fluorescence in situ hybridization (FISH) to diagnose microdeletions. To demonstrate the efficiency, sensitivity, and specificity of PRINS in the diagnosis of microdeletions, we studied groups of patients with Prader Willi/Angelman (PWS/AS) syndrome and DiGeorge/velocardiofacial syndrome (DGS/VCFS). Results obtained by PRINS were then confirmed with the results obtained with FISH. Oligonucleotide primers specific for SNRPN and GABRB3 were used for PWS/AS syndromes. For DGS/VCFS, the primers used were DGCR2/TUPLE1 loci. Labeling patterns obtained by PRINS and FISH were analyzed and scored under a fluorescence microscope. Five normal subjects served as controls and were used for standardization of the PRINS protocol. In all, 20 study patients were involved: 10 PWS/AS and 10 DGS/VCFS. Five of the 10 patients referred with the clinical diagnosis of PWS/AS showed absence of labeling for SNRPN and GABRB3 on one chromosome 15, confirming deletion of the two loci. Similarly, 6 of the 10 patients referred for DGS/VCFS showed deletion for the DGCR2/TUPLE1 loci on one chromosome 22. The remaining patients and controls had normal patterns for all the loci as indicated by FISH and PRINS. Concordant FISH and PRINS results were obtained in all patients and controls studied.