Expression of carbonic anhydrase II (CA II) promoter-reporter fusion genes in multiple tissues of transgenic mice does not replicate normal patterns of expression indicating complexity of CA II regulation in vivo.

Although the proximal, 5' 115 bp of the human carbonic anhydrase II (CA II) gene was sufficient for expression of a reporter gene in some transfected cell lines, we found previously that 1100 bp of this promoter (or 500 bp of the mouse CA II promoter) was not sufficient for expression in transgenic mice. We have now studied the expression of linked reporter genes in mice transgenic for either (1) 11 kb of the human 5' promoter or (2) 8 kb of the human 5' promoter with mouse sequences from the first exon, part of the first intron (since a CpG island spans this region), and the 3' sequences of the gene. Expression was found in both cases, but the tissue specificity was not appropriate for CA II. Although there was a difference in the sensitivity of the assays used, the first construct led to expression in many tissues, while the second construct was expressed only in spleen. These findings indicate considerable complexity of DNA control regions for in vivo CA II expression.