brt encodes a receptor-type protein-tyrosine kinase and was isolated from fetal mouse brain by using a PCR-mediated cloning procedure; this gene is expressed preferentially in the brain of both embryo and adult. Chromosomal locations of the mouse and rat brt genes were determined by fluorescence in situ hybridization using a mouse cDNA fragment as a probe. The brt gene was localized to mouse Chromosome 2F1 and rat Chromosome 3q36.1, where a conserved linkage homology has been identified between the two species. Interspecific backcross analysis genetically demonstrated no recombination between the mouse BRT locus and D2Mit63.