Expression of aspartoacylase (ASPA) and Canavan disease.

[canavan disease]

Canavan disease (CD ) is a neurodegenerative disorder usually presenting in the first six months of life . CD patients can be identified via elevated levels of N-acetyl-l-aspartate in the pattern of urinary organic acids assessed by gas chromatography-mass spectrometry . They are characterized by deficiency of aspartoacylase (aminoacylase 2 ; ASPA ) due to mutations in the ASPA gene . Information on the molecular basis of CD is rather sparse . A lack of expression studies of ASPA mutant proteins in appropriate expression systems has prompted this investigation . Studies with overexpressed ASPA mutant proteins were carried out in the HEK 293 cell line , which provides the authentic human machinery for posttranslational modifications . All ASPA mutants tested (ASPA Arg 168 H is , ASPA Pro 181 Thr , ASPA Tyr 288 Cys , ASPA Phe 295 S er , and ASPA Ala 305 G lu ) showed loss of ASPA activity , which can be explained by the intramolecular effects of the mutations in the enzyme . The mutation p .Phe 295 Ser even leads to absent ASPA mRNA expression , as revealed by quantitative real-time PCR . Using this approach , ASPA gene expression analysis yielded high levels of human ASPA gene expression not only in brain and kidney , but also in lung and liver . More information of ASPA localization in human organs and detailed characterization of mutations leading to a deficiency of ASPA can contribute to a better understanding of this inborn error of metabolism .