Chromosomal localization of ceruloplasmin and transferrin genes in laboratory rats, mice and in man by hybridization with specific DNA probes.

Fragments of the natural rat ceruloplasmin (Cp) gene and cDNA copies of rat Cp and transferring (Tf) mRNAs highly labelled by nick translation with 125I-dCTP were used as specific probes for assignment of these genes to the metaphase chromosomes of rat, mouse and man by in situ hybridization. Both Cp and Tf genes were found to be syntenic in rodents, occupying with high probability the regions 9D and 9F1-3 in mice and 7q11-13 and 7q31-34 in rats respectively. The significant increase in silver grain count over chromosome 15 in rats after hybridization with both the Cp and Tf probes suggests the presence of a related pseudogene cluster on this particular chromosome and thus favours its partial homeology to chromosome 7. The localization of silver grains in metaphase chromosome of man indicates subregional assignment of the Tf gene to 3q21. Use of the rat Cp DNA probe does not indicate synteny of the Cp and Tf genes in man and suggests the existence of a related DNA sequence in 15q11-13. The potential and limitations of the in situ hybridization technique with heterologous DNA probes for gene mapping in mammalian species are discussed.