Molecular and Cellular Endocrinology 252 (2006) 216–223 Canavan disease and the role of N-acetylaspartate in myelin synthesis Aryan M.A. Namboodiri ∗ , Arun Peethambaran, Raji Mathew, Prasanth A. Sambhu, Jeremy Hershfield, John R. Moffett, Chikkathur N. Madhavarao ∗ Department of Anatomy, Physiology and Genetics, USUHS, Bethesda, MD 29814, USA Abstract Canavan disease (CD) is an autosomal-recessive neurodegenerative disorder caused by inactivation of the enzyme aspartoacylase (ASPA, EC 3.5.1.15) due to mutations. ASPA releases acetate by deacetylation of N-acetylaspartate (NAA), a highly abundant amino acid derivative in the central nervous system. CD results in spongiform degeneration of the brain and severe psychomotor retardation, and the affected children usually die by the age of 10. The pathogenesis of CD remains a matter of inquiry. Our hypothesis is that ASPA actively participates in myelin synthesis by providing NAA-derived acetate for acetyl CoA synthesis, which in turn is used for synthesis of the lipid portion of myelin. Consequently, CD results from defective myelin synthesis due to a deficiency in the supply of the NAA-derived acetate. The demonstration of the selective localization of ASPA in oligodendrocytes in the central nervous system (CNS) is consistent with the acetate deficiency hypothesis of CD. We have tested this hypothesis by determining acetate levels and studying myelin lipid synthesis in the ASPA gene knockout model of CD, and the results provided the first direct evidence in support of this hypothesis. Acetate supplementation therapy is proposed as a simple and inexpensive therapeutic approach to this fatal disease, and progress in our preclinical efforts toward this goal is presented. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: NAA; Aspartoacylase; Oligodendrocytes; Spongiform degeneration; Acetate hypothesis Canavan disease was first reported by Myrtelle Canavan in 1931 and was recognized as a distinct disease by Van Bogaert and Betrand in 1949 (Adachi et al., 1973). The clinical symptoms of CD include poor head control, macrocephaly, marked devel- opmental delay, optic atrophy, seizures, hypotonia and death in early childhood (Gascon et al., 1990; Matalon and Michals- Matalon, 2000). Three clinically distinct variants of CD are recognized: (1) the congenital form in which the disease is more severe and is recognizable in the first few weeks of life, (2) the infantile form, the most common form in which the disease is apparent by 6 months of age, and (3) the juvenile form in which the disease manifests only by age 4 or 5 (Adachi et al., 1973). The pathologies associated with CD include cortical and subcor- tical spongy degeneration, myelin defects, dysmyelination and hypertrophy and hyperplasia of astrocytes (Adachi et al., 1973; Matalon et al., 1995). Ultrastructural studies have demonstrated intramyelinic vacuolation, astrocyte hypertrophy and unusually elongated mitochondria within astrocytes (Adachi et al., 1973). ∗ Corresponding authors at: 4301 Jones Bridge Road, Building C, USUHS, Bethesda, MD 20814, USA. Tel.: +1 301 295 3516; fax: +1 301 295 3566. E-mail addresses: anamboodiri@usuhs.mil (A.M.A. Namboodiri), cmadhavarao@usuhs.mil (C.N. Madhavarao). Most of these pathological changes are detectable in the mouse model of CD (Matalon et al., 2000). Initially, diagnosis of CD was confirmed by brain biopsy demonstrating spongy degeneration of the white matter with vacuoles within myelin sheaths, astrocyte swelling and deformed mitochondria. Biochemical analyses have shown that hypomyelination is a characteristic feature of Canavan disease (Matalon and Michals-Matalon, 2000). Patients with CD are found to excrete 10–100-fold higher amounts of NAA in their urine, and deficiency of the NAA degradative enzyme ASPA was demonstrated in their cultured skin fibroblasts (Hagenfeldt et al., 1987; Matalon et al., 1988). NAA levels are also elevated in the blood and cerebrospinal fluid of CD patients (Hagenfeldt et al., 1987; Hamaguchi et al., 1993; Jakobs et al., 1991), and proton nuclear magnetic resonance spectroscopy (MRS) of CD patients has revealed increased NAA levels in the brain (Barker et al., 1992; Wittsack et al., 1996). However, increased urinary NAA is currently the most reliable method for CD diagnosis, and can distinguish it from other leukodystrophies (Bartalini et al., 1992; Divry and Mathieu, 1989). Cloning of the human ASPA gene has enabled molecular genetic studies of CD (Kaul et al., 1993; Namboodiri et al., 2000). Two mutations were found to be prevalent among Ashke- nazi Jewish patients with CD (Kaul et al., 1994). A missense 0303-7207/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.mce.2006.03.016