A high-resolution radiation hybrid map of the proximal region of rat Chromosome 4

Radiation hybrid (RH) mapping has been used to produce genome maps in the h uman and mouse, but as yet the technique has been applied little to other s pecies. We describe the use of RH mapping in the rat, using a newly availab le rat/hamster RH panel, to construct an RH map of the proximal part of rat Chromosome (Chr) 4. This region is of interest because quantitative trait loci (QTLs) for defective insulin and catecholamine action, hypertension, a nd dyslipidemia map to this region. The RH map includes 23 rat genes or mic rosatellites previously mapped to this part of Chr 4, one rat gene not prev iously mapped in the rat, and markers for four new genes, homologs of which map to the syntenic region of the mouse genome. The RH map integrates gene tic markers previously mapped on several rat crosses, increases the resolut ion of existing maps, and may provide a suitable basis for physical map con struction and gene identification in this chromosomal region. Our results d emonstrate the utility of RH mapping in the rat genome and show that RH map ping can be used to localize, in the rat genome, the homologs of genes from other species such as the mouse. This will facilitate identification of ca ndidate genes underlying QTLs on this chromosomal segment.