cDNA cloning and developmental expression of murine carbonic anhydrase-related proteins VIII, X, and XI

To help understand the biological functions of carbonic anhydrase-related proteins (CA-RPs VIII, X, and XI), we obtained cDNA clones of murine CA-RPs X and XI and studied the tissue distribution of all three CA-RPs and their developmental expression in the murine embryonic brain. The amino acid sequences of murine CA-RPs are highly conserved with their human homologues, indicating a fundamental biological role of CA-RPs. Among a panel of vital organs, the strongest mRNA expression of all three CA-RPs was consistently observed in the brain. Immunohistochemical analysis revealed the expression of all three CA-RPs in the neural cell body and neurites. CA-RP X was also observed in the myelin sheath, as demonstrated using the shiverer demyelinated mouse. In murine embryos, CA-RP VIII and X messages first appeared in the middle of the gestation period, while the CA-RP XI message was seen at an early gestational stage and expressed to a lesser extent as gestation progressed. All CA-RPs were expressed in the neuroprogenitor cells in the subventricular area and subsequently detected in the neural cells migrating to the cortex. Although the exact function of CA-RPs is still undefined, these findings suggest an important role of CA-RPs in the CNS.