Mapping of bovine cytokeratin sequences to four different sites on three chromosomes.

The chromosomal location of bovine class I and class II cytokeratin sequences was determined using in situ hybridization and Southern blot hybridization to DNA from hybrid somatic cells. The main signals were found over chromosome region 19q16----qter after in situ hybridization with two probes for the class I cytokeratin gene subfamily (KRT10 and KRT19) and over region 5q14----q23 after hybridization with probes for the class II gene subfamily (KRT1, KRT5, and KRT8). These regions most likely contain the loci of functional cytokeratin genes, with KRT10 and KRT19 mapping to 19q21 and KRT1, KRT5, and KRT8 to 5q21. The in situ hybridization data were corroborated by analysis of a somatic hybrid cell panel. The genes for the class I keratins segregated concordantly with each other and syntenic group U21 but were discordant with the class II keratin genes. The class II keratin genes segregated concordantly with each other and syntenic group U3. Two class II gene probes gave an additional minor signal above chromosome region 5q25----q33 after in situ hybridization, while another class II probe yielded a minor signal above chromosome region 10q31----qter. When the latter probe and an additional linked probe were hybridized to DNAs from a hybrid panel, two independently segregating loci were recognized, one of which cosegregated with the class II subfamily in syntenic group U3 and the other with syntenic group U5. These data confirm the chromosomal assignment of two syntenic groups and allow the assignment of a formerly unassigned syntenic group.