Identification and distribution of aspartoacylase in the postnatal rat brain

Abstract

Aspartoacylase metabolizes N-acetylaspartic acid to produce L-aspartate and acetate. An aspartoacylase deficiency in humans is responsible for Canavan disease, a lethal autosomal recessive leukodystrophy. The role of aspartoacylase in the mammalian brain is unclear. Here we have generated and characterized a highly specific polyclonal antibody against aspartoacylase which recognizes a 37 kDa monomer and a dimer in normal but not in aspartoacylase-deficient rat tissue. Aspartoacylase protein expression sharply increases at P14, peaks at P28 and plateaus thereafter. Biochemical analysis reveals immunoreactivity in cytosolic but not in membrane fractions. Histologically, most abundant expression was observed in white matter tracts and thalamus. On the cellular level, aspartoacylase immunoreactivity is restricted to oligodendrocyte somata in both white and gray matter.

N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

“…et al, 1973;Kirmani et al, 2003) becomes critical in order to liberate the acetate from NAA for the synthesis of acetyl CoA, which is necessary for the synthesis of certain myelin-associated lipids. A number of studies, including the recent demonstrations of the selective localization of ASPA in oligodendrocytes in the CNS Kirmani et al, 2002;Klugmann et al, 2003;Madhavarao et al, 2004), and the increasing NAA concentrations observed by MRS in human fetuses in utero during development (Girard et al, 2005) are consistent with the acetate-deficiency hypothesis of Canavan disease.…”

“…Immunohistochemical studies using polyclonal antibodies to ASPA confirmed that it was expressed in oligodendrocytes (Klugmann et al, 2003). Further, using dual-labeling immunohistochemistry it has been shown that ASPA is definitely expressed strongly in oligodendrocytes in the CNS, but that it is not expressed in astrocytes .…”

Non-genetic therapeutic approaches to Canavan disease

“…Since oligodendrocytes are an important source of CNS ASPA (Bhakoo et al, 2001), if not the most important (Baslow et al, 1999;Kirmani et al, 2002;2003;Klugmann et al, 2003;Mhadavarao et al, 2002;, repopulation of the brain of a CD patient with functional oligodendrocytes could potentially rectify much of the disease phenotype through the restoration of normal NAA metabolism. Neural stem cells have been successfully used to generate oligodendrocytes in the CD mouse model (Surendran et al, 2004) and these oligodendrocytes expressed a myelin-specific enzyme indicative of myelin-producing ability, but clinical outcomes of such a…”

N-Acetyl Aspartate

“…ASPA is predominantly localized to white matter. 10,11 The mechanism by which NAA leaves neurons is not known, although it is likely that transport into oligodendrocytes occurs via the sodium-dependent carboxylate transporter, NaC3. 12,13 The turnover of NAA in the brain is relatively slow, with a half-life of ∼7 h.…”