Expression of transmembrane carbonic anhydrases, CAIX and CAXII, in human development

The study has showed that: 1) HIF-1alpha and CAIX expression co- localized in many, but not all, of the embryonic and early fetal tissues; 2) There is no evidence of co-localization of CAIX and CAXII; 3) CAIX and CAXII expression is closely related to cell origin and secretory activity involving proton transport, respectively. The intriguing finding of rare CAIX-expressing cells in those sites corresponding to stem cell niches requires further investigation.