Sequential expression of murine homeo box genes during F9 EC cell differentiation.

We have isolated and characterized a previously unknown member of the murine homeo box family. The new locus, m31, is located on chromosome 15 and is more homologous to sequences contained in the Drosophila homeotic gene, Antp, than to any other known murine homeo box. We show that this gene encodes a 2.7 kb mRNA which is expressed during mouse embryogenesis and during differentiation of F9 teratocarcinoma cells into parietal endoderm cells. The transcript appears late in this differentiation process and is most abundant at a time when the F9 cells begin to express tissue-specific markers and the expression of another murine homeo box gene, m6, has decreased.