Altered ATP7A expression and other compensatory responses in a murine model of Menkes disease

Mutations in the copper-transporter ATP7A lead to severe neurodegeneration in the mottled brindled hemizygous male (Mo-Br/y) mouse and human patients with Menkes disease. Our earlier studies demonstrated cell-type- and -stage-specific changes in ATP7A protein expression during postnatal neurodevelopment. Here we examined copper and cuproenzyme levels in Mo-Br/y mice to search for compensatory responses. While all Mo-Br/Y neocortical subcellular fractions had decreased copper levels, the greatest decrease (8-fold) was observed in cytosol. Immunostaining for ATP7A revealed decreased levels in MoB'/Y hippocampal pyramidal and cerebellar Purkinje neurons. In contrast, an upregulation ofATP7A protein occurred in MOBr/Y endothelial cells, perhaps to compensate for a lack of copper in the neuropil. Mo(Br/)y astrocytes and microglia increased their physical association with the blood-brain barrier. No alterations in ATP7A levels were observed in ependymal cells, arguing for specificity in the alteration observed at the blood-brain barrier. The decreased expression of ATP7A protein in MOBr/y. Purkinje cells was associated with impaired synaptogenesis and dramatic cytoskeletal dysfunction. Immunoblotting failed to reveal any compensatory increase in levels of ATP7B. While total levels of several cuproenzymes (peptide-amidating monnoxygenase, SOD I, and SOD3) were unaltered in the MOBr/y brain, levels of amidated cholecystokinin (CCK8) and amidated pituitary adenylate cyclase- activating polypeptide (PACAP38) were reduced in a tissue-specific fashion. The compensatory changes observed in the neurovascular unit provide insight into the success of copper injections within a defined neu rodevelop mental period. (c) 2007 Elsevier Inc. All rights reserved.