Search

Mutations in ATP7A lead to at least three allelic disorders: Menkes disease (MD), Occipital horn syndrome and X-linked distal motor neuropathy. These disorders are mainly seen in male individuals, but a few affected females have been described. More than 400 different mutations have been identified in the ATP7A gene. We have conducted several studies in the hope of uncovering the relationship between genotype and phenotype. We have examined the X-inactivation pattern in affected females, the effect of exon-deletions and--duplications, and splice-site mutations on the composition and amount of ATP7A transcript, and we have examined the structural location of missense mutations. The X-inactivation pattern did not fully explain the manifestation of MD in a small fraction of carriers. Most of the affected females had preferential inactivation of the X-chromosome with the normal ATP7A gene, but a few individuals exhibited preferential inactivation of the X-chromosome with the mutated ATP7A gene. The observed mild phenotype in some patients with mutations that effect the composition of the ATP7A transcript, seems to be explained by the presence of a small amount of normal ATP7A transcript. The location of missense mutations on structural models of the ATP7A protein suggests that affected conserved residues generally lead to a severe phenotype. The ATP7A protein traffics within the cells. At low copper levels, ATP7A locates to the Trans-Golgi Network (TGN) to load cuproenzymes with copper, whereas at higher concentrations, ATP7A shifts to the post-Golgi compartments or to the plasma membrane to export copper out of the cell. Impaired copper-regulation trafficking has been observed for ATP7A mutants, but its impact on the clinical outcome is not clear. The major problem in patients with MD seems to be insufficient amounts of copper in the brain. In fact, prenatal treatment of mottled mice as a model for human MD with a combination of chelator and copper, produces a slight increase in copper levels in the brain which perhaps leads to longer survival and more active behavior. In conclusion, small amounts of copper at the right location seem to relieve the symptoms., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Menkes disease is a lethal X-linked recessive disorder of copper metabolism caused by mutations in ATP7A, a copper-transporting ATPase with diverse and important biological functions. Partial deficiency of dopamine-beta-hydroxylase is a biochemical hallmark of this illness due to the normal role of ATP7A in delivery of copper as an enzymatic cofactor. We exploited this fact to develop a diagnostic test for Menkes disease, which proved highly sensitive and specific. The assay has enabled early identification of affected patients, leading to enhanced survival and improved neurodevelopment after early copper treatment, including some completely normal outcomes. In preclinical efforts to develop improved therapies for patients with non-copper-responsive ATP7A mutations, we used brain-directed adeno-associated viral gene therapy to rescue a murine model of the disease. Statistically significant improvement in brain catechol ratios correlated with enhanced survival, and cerebrospinal fluid catechols represent candidate surrogate markers of treatment effect in a future gene therapy clinical trial., (© 2013 Elsevier Inc. All rights reserved.)

Menkes disease is a lethal infantile neurodegenerative disorder of copper metabolism caused by mutations in a P-type ATPase, ATP7A. Currently available treatment (daily subcutaneous copper injections) is not entirely effective in the majority of affected individuals. The mottled-brindled (mo-br) mouse recapitulates the Menkes phenotype, including abnormal copper transport to the brain owing to mutation in the murine homolog, Atp7a, and dies by 14 days of age. We documented that mo-br mice on C57BL/6 background were not rescued by peripheral copper administration, and used this model to evaluate brain-directed therapies. Neonatal mo-br mice received lateral ventricle injections of either adeno-associated virus serotype 5 (AAV5) harboring a reduced-size human ATP7A (rsATP7A) complementary DNA (cDNA), copper chloride, or both. AAV5-rsATP7A showed selective transduction of choroid plexus epithelia and AAV5-rsATP7A plus copper combination treatment rescued mo-br mice; 86% survived to weaning (21 days), median survival increased to 43 days, 37% lived beyond 100 days, and 22% survived to the study end point (300 days). This synergistic treatment effect correlated with increased brain copper levels, enhanced activity of dopamine-β-hydroxylase, a copper-dependent enzyme, and correction of brain pathology. Our findings provide the first definitive evidence that gene therapy may have clinical utility in the treatment of Menkes disease.

This Review summarizes recent advances in understanding copper-transporting ATPase 1 (ATP7A), and examines the neurological phenotypes associated with dysfunction of this protein. Involvement of ATP7A in axonal outgrowth, synapse integrity and neuronal activation underscores the fundamental importance of copper metabolism to neurological function. Defects in ATP7A cause Menkes disease, an infantile-onset, lethal condition. Neonatal diagnosis and early treatment with copper injections enhance survival in patients with this disease, and can normalize clinical outcomes if mutant ATP7A molecules retain small amounts of residual activity. Gene replacement rescues a mouse model of Menkes disease, suggesting a potential therapeutic approach for patients with complete loss-of-function ATP7A mutations. Remarkably, a newly discovered ATP7A disorder-isolated distal motor neuropathy-has none of the characteristic clinical or biochemical abnormalities of Menkes disease or its milder allelic variant occipital horn syndrome (OHS), instead resembling Charcot-Marie-Tooth disease type 2. These findings indicate that ATP7A has a crucial but previously unappreciated role in motor neuron maintenance, and that the mechanism underlying ATP7A-related distal motor neuropathy is distinct from Menkes disease and OHS pathophysiology. Collectively, these insights refine our knowledge of the neurology of ATP7A-related copper transport diseases and pave the way for further progress in understanding ATP7A function.

Epilepsy is a major feature of Menkes disease, an X-linked recessive infantile neurodegenerative disorder caused by mutations in ATP7A, which produces a copper-transporting ATPase. Three prior surveys indicated clinical seizures and electroencephalographic (EEG) abnormalities in a combined 27 of 29 (93%) symptomatic Menkes disease patients diagnosed at 2 months of age or older. To assess the influence of earlier, presymptomatic diagnosis and treatment on seizure semiology and brain electrical activity, we evaluated 71 EEGs in 24 Menkes disease patients who were diagnosed and treated with copper injections in early infancy (≤6 weeks of age), and whose ATP7A mutations we determined. Clinical seizures were observed in only 12.5% (3/24) of these patients, although 46% (11/24) had at least one abnormal EEG tracing, including 50% of patients with large deletions in ATP7A, 50% of those with small deletions, 60% of those with nonsense mutations, and 57% of those with canonical splice junction mutations. In contrast, five patients with mutations shown to retain partial function, either via some correct RNA splicing or residual copper transport capacity, had neither clinical seizures nor EEG abnormalities. Our findings suggest that early diagnosis and treatment improve brain electrical activity and decrease seizure occurrence in classical Menkes disease irrespective of the precise molecular defect. Subjects with ATP7A mutations that retain some function seem particularly well protected by early intervention against the possibility of epilepsy.

Protein translation ends when a stop codon in a gene's messenger RNA transcript enters the ribosomal A site. Mutations that create premature stop codons (nonsense mutations) typically cause premature translation termination. An alternative outcome, read-through translation (or nonsense suppression), is well known in prokaryotic, viral, and yeast genes but has not been clearly documented in humans except in the context of pharmacological manipulations. Here, we identify and characterize native read-through of a nonsense mutation (R201X) in the human copper transport gene, ATP7A. Western blotting, in vitro expression analyses, immunohistochemistry, and yeast complementation assays using cultured fibroblasts from a classic Menkes disease patient all indicated small amounts of native ATP7A(R201X) read-through and were associated with a dramatic clinical response to early copper treatment.

Menkes disease is a fatal neurodegenerative disorder of infancy caused by defects in an X-linked copper transport gene, ATP7A. Evidence from a recent clinical trial indicates that favorable response to early treatment of this disorder with copper injections involves mutations that retain some copper transport capacity. In three unrelated infants, we identified the same mutation, G727R, in the second transmembrane segment of ATP7A that complemented a Saccharomyces cerevisiae copper transport mutant, consistent with partial copper transport activity. Quantitative reverse transcription-polymerase chain reaction studies showed approximately normal levels of ATP7A(G727R) transcript in two patients' fibroblasts compared to wild-type controls, but Western blot analyses showed markedly reduced quantities of ATP7A, suggesting post-translational degradation. We confirmed the latter by comparing degradation rates of mutant and wild-type ATP7A via cyclohexamide treatment of cultured fibroblasts; half-life of the G727R mutant was 2.9h and for the wild-type, 11.4h. We also documented a X-box binding protein 1 splice variant in G727R cells-known to be associated with the cellular misfolded protein response. Patient A, diagnosed 6 months of age, began treatment at 228days (7.6 months) of age. At his current age (2.5 years), his overall neurodevelopment remains at a 2- to 4-month level. In contrast, patient B and patient C were diagnosed in the neonatal period, began treatment within 25 days of age, and show near normal neurodevelopment at their current ages, 3years (patient B), and 7 months (patient C). The poor clinical outcome in patient A with the same missense mutation as patient A and patient B with near normal oucomes, confirms the importance of early medical intervention in Menkes disease and highlights the critical potential benefit of newborn screening for this disorder.

Copper is an essential component of a number of important enzymes. Efficient systems have developed for providing sufficient copper for essential functions, while eliminating excess to avoid tissue toxicity. Copper transport is disrupted in two human diseases: Wilson disease and Menkes disease. Both have defects in copper transporting membrane proteins. Many other proteins are involved in copper transport. Some of these proteins have been identified through a study of the similar copper pathway in yeast. This suggests other copper transport diseases are yet to be discovered. Molecular diagnosis holds promise for reliable diagnosis of patients. Testing of flanking markers is a reliable way to detect presymptomatic sibs of a definite patient.