Identification of Y chromatin directly in gonadal tissue by fluorescence in situ hybridization (FISH): Significance for Ullrich-Turner syndrome screening in the cytogenetics laboratory

The presence of Y chromatin in individuals with Ullrich-Turner syndrome (UT S) confers a risk for gonadoblastoma. In mosaic cases, little is known abou t Y chromatin distribution in gonads. Fluorescence in situ hybridization (F ISH) is a direct approach to assess the extent of Y chromatin mosaicism in gonads. Gonadal tissue from four patients with mosaic karyotypes were analy zed by routine cytogenetics and FISH with X and Y centromere probes. Y chro matin was present in gonads in varying percentages in these patients. The d istribution of Y chromatin in gonads of UTS individuals did not completely correlate with that found in blood lymphocytes, The finding of Y chromatin in the blood samples from these patients prompted the development of a scre ening strategy in our cytogenetics laboratory to detect low-level Y chromat in mosaicism in patients with UTS, (C) 2000 Wiley-Liss, Inc.