Two diverged human homeobox genes involved in the differentiation of human hematopoietic progenitors map to chromosome I, bands q41–42.I

Proteins encoded by homeobox containing genes are sequence-specific DNA binding proteins implicated in the control of gene expression in both developing and adult tissues. Two recently characterized human homeobox genes, HB9 and HB24, are highly expressed in CD34-positive marrow cells but not in CD34-depleted marrow cells. Their expression is readily down-regulated during the differentiation of hematopoietic progenitors to specific cell lineages. In this study, genomic DNA fragments isolated with HB9 (3 kb) and HB24 (6 kb) cDNAs were used to map their chromosomal location by fluorescence in situ hybridization. Both HB9 and HB24 DNA probes gave specific hybridization signals on chromosome 1. The hybridization loci were identified by combining fluorescence images of the probe signals with fluorescence banding patterns generated by cohybridization in situ with an Alu probe (R-like banding) and by DAPI staining (G-like). The results demonstrate that the loci of the HB24 and HB9 genes are within bands 1q41-q42.1. A cohybridization experiment utilizing both probes with two-color fluorescence imaging could not resolve separate loci for the two genes.