Mutation Analysis and Expression of the Mottled Gene in the Macular Mouse Model of Menkes Disease

Abstract

The gene for Menkes disease, an X-linked disorder of copper transport, has recently been identified and shown to encode a copper-transporting P-type ATPase. The macular mutant mouse has been proposed as an animal model for Menkes disease. In the present study, we report the finding of a missense mutation in the mottled gene of the macular mouse. A single base change, T to C, at nucleotide position 4223, is predicted to result in an amino acid change from serine to proline at residue 1382 in the eighth transmembrane domain. This mutation differs from the 6-bp deletion we find in brindled cDNA. With validation of macular as an animal model of Menkes disease, we compared mottled gene expression in the intestine, kidney, and brain of macular and normal mice. In Northern analyses an 8.3-kb transcript was detected in the intestine, kidney, and brain of both normal and macular mice, with the level of transcript in macular approximately 80% that of normal. In situ hybridization studies revealed that the mottled gene was clearly expressed in intestinal epithelial cells, Paneth cells, and renal proximal tubular cells of both normal and macular mice. In normal brain, mottled gene expression was most intensely observed in the choroid plexus, in Ammon's born and the dentate gyrus in the hippocampus, in Purkinje cells, and the granular layer of the cerebellum. The intensity and localization of the signals in the brain of macular mice were similar to those of the controls. The distribution of expression of mottled is correlated with cells and tissues showing histopathology or abnormal copper sequestration in macular and other mutants.

The copper transporter CTR1 provides an essential function in mammalian embryonic development

“…Like the Ctr1 null mutant, many alleles at the mottled locus (Atp7a), including dappled and tortoiseshell, die in utero (26 -28). The abundant expression of both Ctr1 and Atp7a in the choroid plexus supports this structure as an important copper port for the brain (24,29,30). The brain may be particularly vulnerable to reduced CTR1 levels, as evidenced by our atomic absorption studies, because copper might pass first through the choroid Fig.…”

Role of the Menkes copper-transporting ATPase in NMDA receptor-mediated neuronal toxicity

“…In children with Menkes disease, an impairment in copper acquisition in utero due to loss-of-function mutations in the gene encoding a coppertransporting ATPase, Atp7a, results in fatal neurodegeneration associated with intractable seizures, severe hypotonia, and profound developmental delay (8). Pathologic analysis of brain tissue from affected patients reveals neurodegeneration in the cerebral cortex, cerebellum, and hippocampus, consistent with the known sites of the expression of Atp7a within the developing central nervous system (9)(10)(11)(12)(13)(14).…”

Copper-trafficking efficacy of copper-pyruvaldehyde bis(N4-methylthiosemicarbazone) on the macular mouse, an animal model of Menkes disease

“…In a copper-supplement study in the MD model mice, male hemizygous macular mice and normal littermate controls were used. Macular mice arose from the C3H f inbred strain and possess a single base change (4223T→C, exon 22) in the Atp7a gene (14,15). All procedures involving animals were approved by the Animal Care and Use Committees of the Tohoku University School of Medicine and Teikyo University School of Medicine.…”

“…Among them, macular mice are one of the closest models to the classical form of MD; hemizygous males exhibit MD-related symptoms and require copper injections early in life to survive (13)(14)(15). In this study, we investigated the copper-trafficking efficacy of Cu-PTSM to the critical organs in macular mice.…”