Developmental and spatial patterns of expression of the mouse homeobox gene,Hox2.1

Abstract

The H ox 2.1 gene forms part of a cluster of homeo-box -containing genes on mouse chromosome 11. Analysis of Hox2.1 cDNAs isolated from an -day p.c. mouse embryo library predicts that the gene encodes a 269 amino acid protein (Mr, 29432). This deduced protein contains a homeobox 15 amino acids from the carboxy terminus and is very rich in serine and proline. A second partially conserved region present in several other genes containing homeo-boxes, the hexapeptide De-Phe-Pro-Trp-Met-Arg, is located 12 amino acids upstream of the homeodomain and is encoded by a separate exon. Analysis of Hox 2.1 gene expression reveals a complex and tissue-specific series of RNA transcripts in a broad range of feta] tissues (lung, spinal cord, kidney, gut, spleen, liver and visceral yolk sac). Comparison of the temporal patterns of gene expression during development and in the adult suggests that Hox2.1 is regulated independently in different tissues. Evidence is also presented that transcripts from other loci have extensive homology to the Hox2.1 gene in sequences out-side of the homeobox. In situ hybridization shows that Hox2.1 transcripts are regionally localized in the spinal cord in an apparent anterior–posterior gradient extending from the hind brain. The distribution of RNA also displays a cell-type specificity in the. lung, where mesodermal cells surrounding the branching epithelial cell layer accumulate high levels of Hox2.1 transcripts.