The present invention provides a recombinant DNA construct comprising a coding sequence encoding human ASP2 and a brain-specific calcium calmodulin kinase promoter sequence which is operably linked to the coding sequence. The present invention further provides a transgenic non-human animal whose genome incorporates a polynucleotide comprising a coding sequence which encodes the human ASP2 protein wherein the coding sequence is operably linked to a brain-specific calcium calmodulin kinase II promoter.