A target of the HoxB5 gene from the mouse nervous system

An epitope-specific antibody against the protein product of the murine HoxB5 gene was used to select an enriched library of Hox target sequences. Genomic DNA was purified by immunoaffinity chromatography, using glutaraldehyde-cross-linked chromatin from CNS of mouse embryos at gestational day 15. Screening was done by colony hybridization with TAAT-containing oligonucleotides, filter DNA-protein binding, and gel mobility shift assay. Nucleotide sequencing identified a 910 bp DNA fragment, containing a consensus Antennapedia-like binding site, and identical in 640 bps at 3' end of the clone to the promoter of the SPI3 gene, which encodes a serine protease inhibitor protein [Sun, J., Rose, J.B. and Bird, P., J. Biol. Chem., 270 (1995) 16089-16096]. In situ hybridization experiments were performed to see if a correlation could be found between the expression patterns the SPI3 and the HoxB5 genes. Using a 120 bp cDNA fragment as probe, SPI3 expression was detected mainly in the CNS of 15 day mouse embryos, a pattern which is similar to that of the HoxB5 gene at this stage [Hogan, B.L., Holland, P.W. and Lumsden, A., Cell Diff. Dev., 25 Suppl. (1988) 39-44; Sakach, M. and Safaei, R., Int. J. Dev. Neurosci., 14 (1996) 567-573]. In conclusion, data presented here suggest that the SPI3 gene is a candidate target of the HoxB5 gene in vertebrate embryos.