Sequence analysis of the homeobox-containing exon of the murine Hox-4.3 homeogene.

A homeobox-containing gene * was detected by Southern analysis of a cosmid spanning a region of the murine HOX-4 complex between Hox-4.4 (Hox-5.2) and Hox-4.2 (Hox-5.1) with a probe derived from the Hox-4.2 homeobox. The sequence of a cross-hybridizing region revealed an open reading frame encoding an Antennapedia (Antp) class homeodomain highly homologous to the products of human HOX4C (Hox-5.4/HOX4E), mouse Hox-3.1 and Hox-2.4. This, together with strong conservation of sequences 3' to the homoebox, indicates that we have cloned the murine Hox-4.3 gene. No other homeobox sequences were detected in this screen suggesting that the HOX-4 complex lacks paralogous genes represented in the equivalent regions of other HOX loci.     

The murine genes Hox-5.1 and Hox-4.1 belong to the same HOX complex on chromosome 2

Two different loci of Antennapedia-related homeobox-containing genes have been shown to map to mouse chromosome 2: the HOX-5 complex and the Hox-4.1 gene. These independently derived loci are likely to be parts of a single gene complex, although their close linkage has not yet been demonstrated. Since cosmid walks to extend the HOX-5 cluster and to potentially link the two loci were unsuccessful, we have used large restriction fragments separated by pulsed-field gel electrophoresis to demonstrate the linkage between probes from the HOX-5 region and sequences near Hox-4.1. To further define the distance between the two linked loci, we screened a NotI jumping library with sequences near the Hox-5.1 gene to obtain a marker within the region predicted to contain Hox-4.1. The jumping endpoint lies within genomic clones from a lambda phage walk extending from the 5' end of Hox-4.1, and thus provides clear evidence of linkage between the two Hox loci. Our results demonstrate that Hox-4.1 lies approximately 35 kb downstream of the Hox-5.1 gene and that the two loci do indeed thus constitute parts of the same HOX complex.