Characterization of brain ecto-apyrase: evidence for only one ecto-apyrase (CD39) gene

A rat brain cDNA coding for ecto-(Ca,Mg)-apyrase activity was isolated using human CD39 cDNA and functionally expressed in COS-7 cells. The gene codes for a protein with high similarity to human (75% identity) and murine (90% identity) CD39. It is expressed in primary neurons and astrocytes in cell culture as well as in kidney, liver, muscle and spleen. Southern analysis of the mouse genome suggests that there may be a single copy of the ecto-apyrase gene. Interestingly, the human CD39 gene cytologically co-localizes with the susceptibility gene involved in human partial epilepsy with audiogenic symptoms; such a coincidence is consistent with reports on the deficiency of ecto-apyrase activity in the brains of humans with temporal lobe epilepsy and in those of mice with audiogenic seizures.