LOCALIZATION OF THE MURINE CHOLECYSTOKININ-A AND CHOLECYSTOKININ-B RECEPTOR GENES

We have determined the chromosomal locations of the two cholecystokini n (CCK) receptor genes in the mouse. Genetic localization utilized an interspecific backcross panel formed from the cross (C57BL/6J x Mus sp retus) F-1 x Mus spretus. Genomic DNAs from 94 individuals in the back cross were analyzed by Southern hybridization with rat CCKA and CCKB r eceptor cDNA probes. Unique map positions were determined by haplotype analysis with 650 previously mapped loci in the mouse backcross. The CCKA receptor gene (Cckar) mapped to mouse Chromosome (Chr) 5, in tigh t linkage with the DNA marker D5Bir8. The CCKB receptor gene (Cckbr) m apped to mouse Chr 7, tightly linked to the beta-hemoglobin locus (Hbb ). This localization places Cckbu in the same region as the mouse obes ity mutation tubby (tub), which also maps near Hbb (2.4 +/- 1.4 cM). S ince CCK can function as a satiety factor when administered to rodents , localization of Cckbr near the tub mutation identifies this receptor as a possible candidate gene for this obesity mutation.