Localization and genetic linkage of the human immunoglobulin heavy chain genes and the creatine kinase brain (CKB) gene: identification of a hot spot for recombination.

The immunoglobulin heavy chain (IGH) gene cluster and the gene coding for the brain form of the enzyme creatine kinase (CKB) have previously been localized to chromosome 14, at 14q32.3 and 14q32, respectively. Here we report more precise regional localization of these genes by dosage studies using DNA from a child hemizygous for the region from 14q32.32 to 14qter. CKB and IGH are present in a single dose in the proband. Dosage studies in a second patient with a similar but smaller deletion due to a ring chromosome 14 show that CKB is proximal to the IGH cluster. An EcoRI restriction site polymorphism was found with probes for the CKB gene. Linkage analysis of family data indicates that CKB is closely linked to IGH. Linkage analysis also revealed unusually high recombination (beta = 3.2%) between the C delta and C gamma 3 genes of the IGH constant region, which are only 60 kb apart. This finding, in combination with a previous observation of linkage equilibrium in the region, suggests that the C delta-C gamma 3 region contains a recombination hot spot.