SPECIFIC EXPRESSION IN ADULT MICE AND POSTIMPLANTATION EMBRYOS OF A TRANSGENE CARRYING THE HISTONE H1(0) REGULATORY REGION

Histone H1(0), a variant of the H1 group, has been found associated wi th the repressed state of chromatin and its content is increased in te rminally differentiated cells. We have cloned a mouse H1(0) histone ge ne and introduced the promoter region, ligated to the beta-galactosida se reporter gene, into transgenic mice. By histochemistry we demonstra ted a strong expression of the transgene in adult kidney, testis and b rain. Intestine, uterus and ovarium were also positive. This expressio n followed the same pattern as that of the endogenous H1(0) gene, as d emonstrated by in situ hybridization with a non-coding fragment of the mRNA, by Northern analysis, and by immunofluorescence with specific a ntibodies. In post-implantation embryos, the expression was very low u p to day ten p.c. At this time, most of the X-Gal staining was found i n the brain, retina and some of the large blood vessels. Hence, expres sion of the transgene as well as of the endogenous H1(0) gene is not e xclusively linked to a differentiated phenotype or to a reduced cell p roliferation capacity.