A novel multicolor hybridization scheme applied to localization of a transcribed sequence (D10S170/H4) and deletion mapping in the thyroid cancer cell line TPC-1

The sequence-tagged site (STS) D10S170, also referred to as H4, is a gene of unknown function. Its 5' end was found fused to the catalytic domain of the RET protooncogene to generate RET/PTC1, the most common form of PTC oncogenes in human papillary thyroid carcinoma. This gene has previously been assigned to a very large genomic region, 10q11.22 → q22.1. Here, we describe the application of a novel hybridization scheme to the physical and genetic mapping of D10S170. First, we selected a homologous large-insert DNA clone from a human P1 library by filter hybridization and confirmed its authenticity by Southern blot analysis. Triple-color fluorescence in situ hybridization (FISH) experiments mapped this clone to 10q21.2 → q21.3. 'Binning' experiments were performed using a quadruple-color FISH approach aimed toward placing the gene in a genetic interval defined by differentially labeled P1 DNA probes containing known polymorphic markers. We found that multicolor FISH greatly expedites chromosomal mapping. Finally, we applied our FISH approach to determine the extent of deletion involving this locus (D10S170) in a papillary thyroid cancer cell line, TPC-1.