The transgene comprises a full-length, 1865 base pair mouse cDNA encoding the short (38.7 kDa), normally brain-specific enzyme isoform under control of the human ubiquitin C promoter. The coding sequence is followed by the SV40 splice and polyadenylation signals, and the entire construct is flanked by loxP sequences. Protein levels detected by western blot analysis are similar in heart, kidney and lung of transgenic mice homozygous for a targeted mutation of the gene and of wild-type mice, but higher in brain and much lower in liver of the former.