Physical linkage of the murine Hox-b cluster and nerve growth factor receptor on yeast artificial chromosomes.

Evidence derived from sequence comparisons and the genomic organization of the murine Antennapedia-class homeobox gene clusters suggest that they arose from a primordial cluster through a process of gene duplication and divergence followed by cluster duplication. A large chromosomal domain surrounding the ancestral homeobox cluster also appears to have been duplicated and has remained relatively stable since the divergence of humans and rodents. To test the extent of the duplicated chromosomal domain, we have initiated physical mapping studies of the regions surrounding the four murine homeobox clusters using pulsed-field gel electrophoresis and yeast artificial chromosome cloning. In this study, we present a long-range restriction map of mouse chromosome 11 spanning 1500 kb in the region surrounding the Hox-b cluster. We have determined that the gene for the nerve growth factor receptor is tightly linked to the Hox-b complex and is located within 50 kb of the Hox-b 1 gene at the 3' end of the cluster. Four yeast artificial chromosomes have been isolated and characterized by the polymerase chain reaction, long-range restriction mapping, and Southern blotting. Two clones of 150 and 300 kb contain the entire Hox-b cluster and the nerve growth factor receptor gene. A 440-kb clone contains the 3' end of the Hox-b cluster, the nerve growth factor receptor gene, and extends downstream. A 210-kb clone contains the 5' end of the Hox-b cluster and extends upstream. These clones confirm the pulsed-field restriction map of uncloned mouse DNA and represent a contig of approximately 600 kb of cloned material from mouse chromosomes 11.