Clustered homeo boxes are differentially expressed during murine development.

A murine homeo box (m6-12) known to be expressed during differentiation of embryonal carcinoma cells lies within a cluster of homeo boxes located in 30 kilobase pairs of genomic DNA. We have established the organization of the boxes within this complex, as well as the nucleotide sequence of a second box, m5-4. Similar to the m6-12 box, expression of novel m5-4 transcripts is induced upon differentiation of embryonal carcinoma cells. Transcripts of genes containing m6-12 were found in embryonic tissue during almost all stages of prenatal development studied, whereas expression of m5-4 was detected only in 12 day embryonic tissue. Finally, we have described the differential expression of these homeo-box-containing regions in various adult tissues.