Copper comes of age in Melbourne

Abstract

When we were asked to produce articles for this volume, it seemed appropriate to us to co-author an article on the history and impact of copper research in Melbourne. It is appropriate because over many years, decades in fact, we worked closely together and with Professor David Danks to identify the molecular defect in Menkes disease. This work was always carried out with the intention of understanding the nature of the copper homeostatic mechanisms and a “copper pathway” in the cell, that David had the prescience to predict must exist despite scepticism from granting agencies! He indeed inspired us to pursue research careers in this field. This article outlines some of this history.

Background to trace element research in Australia

The foundation of much of the current research into the biological roles of copper was laid by pioneering work that demonstrated the essentiality of copper and the importance of adequate copper nutrition for animals in agriculture. This work took particular prominence in Australia for the good reason that many of the soils of this ancient continent were depleted of trace elements. When this fact was recognized, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) undertook extensive research into the effects of trace element deficiencies in domestic animals.

Sheep played an important part in the copper story. This species was of particular importance to Australia in the first half of the 20th century, as wool production was vital to the Australian economy. As it happens, sheep have a distinct pattern of copper homeostasis: on the one hand they are very susceptible to copper deficiency, leading to defects in keratin formation and production of economically useless “steely wool”; on the other hand if provided with even a small excess of copper they accumulate toxic levels of copper in the liver. The hepatotoxicity is exacerbated by the consumption of plants containing pyrrolizidine alkaloids, which sheep eat in times of drought, a common occurrence in Australia. An early observation showing the importance of copper in neurological development and myelination in particular is the disease “swayback”, which was found to be due to copper-deficiency in lambs in Western Australia.¹ The changes in wool exhibited by copper-deficient sheep and “swayback” symptoms were an important clue to solving the Menkes disease puzzle, as we shall see later.

Copper was not the only trace element deficiency common in Australian soils, and research by Prof. Eric Underwood and colleagues was very important in identifying the effects of the deficiency of the various trace elements in Western Australian soils. Prof. Underwood produced the book “Trace Elements in Human and Animal Nutrition”, which remains an important source of background information for workers in the trace element field.² He was involved in organising the Trace Elements in Man and Animals (TEMA) meeting held in Perth in 1981, but sadly passed away shortly before the meeting. It was at this Perth meeting that Jim first met Joe Prohaska.

The importance of trace element research in Australia led to the development of a key instrument that allowed rapid and accurate measurement of many different elements in biological samples: the Atomic Absorption Spectrophotometer (AAS). Another CSIRO scientist, Dr Alan Walsh, invented this instrument, and it has played a vital role in our research as well as in all other trace element laboratories.

David Danks's interest in copper

David Danks was a clinical geneticist who was a mentor to both Jim and Julian. David was a remarkable man who essentially established clinical genetics in Australia.

After qualifying in Medicine in Melbourne in 1954, he developed a lifelong interest in genetic disorders, at a time when these disorders were seen to be rare and medically unimportant. He saw, however, that genetic diseases were “experiments of nature”, in the memorable phrase of the famous English physician Archibald Garrod, and could be very useful in identifying unknown biochemical processes. David became Professor of Paediatrics in the Royal Children's Hospital, Melbourne, and his passion for clinical genetics was encouraged by Dame Elizabeth Murdoch, then president of the hospital. He went for overseas training with the top Medical Geneticists of the time, including Victor McKusick. On his return to Melbourne he established the Genetics Research Unit in 1967. Jim's first interaction with David Danks was spending a University student summer break period at the Genetics Research Unit doing a mini-research project (but not on copper!).

David encountered cases of the inherited copper disorder, Wilson disease, in the hospital, and his desire to understand and better treat this potentially fatal disorder stimulated his interest in copper disorders. Showing his flexibility of mind, he found out about the copper research being carried out on animals in CSIRO, and in this way he learnt about the many clinical features exhibited by copper deficient animals, mainly sheep (steely wool, swayback, osteoporosis) and pigs (arterial tortuosity). He was thus mentally primed to recognize these symptoms and solve the mystery of Menkes disease as an inherited systemic copper deficiency disease.

Menkes disease is a disorder of copper homeostasis: early days in the search for the biochemical defect

In 1962 John Menkes had reported an unusual X-linked mental retardation condition with a complex clinical presentation³ which included what was initially described as kinky hair. The disorder was named Menkes disease (MD) (initially Menkes syndrome) in recognition of this discovery. No obvious biochemical basis for the disorder was apparent at that time. In the early 1970s several MD patients were seen by David Danks. He realised that many of the symptoms of the boys with the disorder were the same as those he had seen in copper deficient animals, and so he ordered copper tests on serum and other tissue samples using AAS. The results were fascinating. As expected from the copper deficiency features, the copper concentrations in many tissues were low, however, samples from the gut were high. David speculated that there could be a disorder of copper absorption, which he later confirmed with copper radioisotope studies.⁴ This was an important discovery that paved the way into the modern era of molecular analysis of copper homeostasis. David of course realised the potential importance of his finding, and developed a team of scientists to pursue the biochemical basis of the disorder.

It was at this time that Jim rejoined the Genetics Research Unit (after an initial post-doctoral period at the Walter and Eliza Hall Institute), and was tasked with finding the basic defect in Menkes syndrome (a tall order in retrospect, with the tools available at that time).

Jim's initial findings were on the copper accumulation phenotype of cultured cells from MD patients due to a defect in copper efflux.⁵ Although counter-intuitive for a copper-deficiency disorder, it explained how systemic copper deficiency was caused by malabsorption of copper due to its accumulation in gut epithelial cells. He developed assay systems using the copper radioisotope copper-64. This led to a prenatal diagnostic test for MD. A group in Denmark led by Dr Nina Horn was making similar discoveries, but Jim's focus was on the copper efflux defect which was linked to copper accumulation.

Jim also investigated copper homeostasis in mottled mouse mutants, including development of treatment protocols.⁶ These mutants had the same defect as in MD and were a powerful and precise mouse model for MD. This had been discovered by Dr David Hunt in London⁷ who Jim met in London. David later spent a sabbatical period at the University of Melbourne and Royal Children's Hospital, and remains a friend and colleague of Jim and Julian.

Jim (who had taken up an appointment as lecturer in the Department of Genetics University of Melbourne in 1979 but continued collaboration with David and Julian) developed and utilised several model systems for studying copper homeostasis in which he utilised genetic approaches for identifying genes and proteins involved. Initially these involved the isolation of copper-resistant Chinese Hamster Ovary (CHO) cells. He used CHO cells as metallothionein genes are not expressed in these cells, hence increasing the likelihood of unmasking other mechanisms of resistance. Indeed these copper-resistant cells later played a pivotal role in confirming the function of the Menkes protein as a copper efflux transporter (described below). Their copper resistance was due to an amplification of the “Menkes” gene (ATP7A)⁸ a finding that was made possible by Julian's cloning of ATP7A.

Jim, together with Barry Lee and co-investigators at the Genetics Dept., University of Melbourne, investigated copper homeostasis in E. coli as a model system, and several genes involved in copper homeostasis were identified. Jim, together with Dr Richard Burke (a post-doc in his lab. at the time) later developed Drosophila as a powerful genetic system to investigate copper homeostasis.⁹

Molecular biology studies of copper

During the 1970s the techniques of recombinant DNA production were being developed around the world. The first genes were being cloned and gene libraries were being constructed. Molecular analysis of the defects in globin genes in thalassemia were being reported, and many more of the easy to clone genes affected in genetic metabolic disorders with Mendelian inheritance were soon to follow. David was keen to establish molecular cloning techniques in the Genetics Research Unit, and appointed Julian in 1979 to undertake this task. At the time, the only approach to cloning a gene proceeded from knowledge of the affected protein.

With MD, the affected protein was completely unknown, but the heavy metal binding proteins, metallothioneins (MTs), were known and were considered a possible candidate for the defect in MD. So Julian set out to clone the MT genes with the intention of studying their structure and expression in MD patients. The first joint paper by Julian and Jim was published in 1981 and concerned the copper induction of MT mRNA.¹⁰ In 1982, Julian published the cloning of a rat MT cDNA.¹¹

We did not realize at the time that MT gene regulation was being studied by Arturo Leone, the co-founder of the International Copper Meetings in Italy, in Dean Hamer's Laboratory of Biochemistry at the National Cancer Institute, Bethesda, Maryland, USA. Interestingly, another key player in the copper field, Dennis Thiele, was in Hamer's lab at the same time and Dennis and Arturo became good friends. Dennis Thiele was working on induction of MTs in yeast. Julian thinks he can recall the moment that Dean Hamer became particularly interested in Menkes disease and the mottled mouse mutants. It was at an International Congress of Biochemistry meeting in Perth, Western Australia in 1982. Dean spotted a poster from our group describing the mice and Menkes disease and showed an intense interest in the results. In 1985 Arturo published an important paper in Cell describing the abnormal regulation of MT genes in Menkes fibroblasts.¹² The results from this paper suggested that the elevation of MTs in Menkes fibroblasts were as a result of copper accumulation and that MTs were not directly involved in the disease.

At this point we did not have any other candidates to chase, despite the best efforts of Jim and the team chasing possible leads using biochemical approaches.

Julian at this stage turned his attention to investigating sheep copper metabolism, in particular the structure and regulation of MT genes.¹³ He collaborated with a colleague in Perth, Prof. John Howell, who had a long-term interest in sheep copper toxicity and pyrrolizidine alkaloid poisoning. David Danks viewed the copper poisoned sheep as a possible animal model for Wilson disease. Unfortunately we did not find any abnormalities in MT genes or expression in the sheep, but carried out some interesting studies on sheep MT gene structure and expression.

The identification of the gene affected in MD was not solved by biochemical approaches, but had to await the development of positional cloning strategies that allowed the isolation of disease genes without any prior knowledge of the protein involved.

The cloning of the Menkes gene

It was the late 1980s when the human genetics community was abuzz with excitement about the new approach to cloning genes involved in previously intractable genetic disorders. The “positional cloning” approach involved knowledge of the location of the gene on a chromosome but nothing about the nature of the encoded protein. The gene affected in chronic granulomatous disease was reported in 1986 and was followed soon after by the isolation of the Duchenne muscular dystrophy gene. Both genes were isolated by making use of a chromosomal abnormality, such as a deletion or translocation, which narrowed the candidate interval to a manageable size.

We were of course well aware of the advances in this area, but could not see how to feasibly apply this approach to the cloning of the MD gene. Even though the MD gene was on the X-chromosome, its position had not been mapped to a small enough interval. Then a key paper was published by Jim Higgins reporting an unusual case of a female with MD.¹⁴ What was particularly significant was this female had a chromosomal abnormality, an X-autosome translocation that was undoubtedly responsible for her disease. This meant that most likely, the translocation disrupted the MD gene; thus the translocation break point was the key locator of the gene.

We decided to try and obtain the cell line from the female MD patient so we could use it for cloning of the Menkes gene. In 1987, David wrote to Jim Higgins to see if he would send the cell line. He declined on the grounds that he was aiming to clone the gene himself, in collaboration with another group. So we resigned ourselves with the prospect of using the cloned gene to study our Menkes disease patients. Years passed but there was no sign of the Menkes gene cloning report. Then in June 1991 a paper was published from Tom Glover's laboratory in Ann Arbor reporting the detailed mapping of the translocation breakpoint.¹⁵ Tom had collaborated with Jim Higgins as they were colleagues, both being cytogeneticists. Assuming that they would be well on the way to cloning the gene, Julian wrote to Tom Glover, asking about the progress and, as he was thinking about a possible sabbatical, whether he could spend some time in Tom's lab working on the Menkes gene project. As it turned out this was fortuitous timing, as Tom's group had not yet isolated the gene and needed a molecular biologist to complete this work. So Julian relocated his family to Michigan, USA, arriving in November to start the exciting nine months that led to the isolation of the Menkes gene.

The translocation cell line had arrived by various paths in three other laboratories who were all trying to isolate the Menkes gene. We knew about these groups, who included Tony Monaco, a top class positional cloner, and Jane Gitschier, another excellent molecular biologist. So competition was intense. The end result of a lot of exciting work was that Nature Genetics agreed to publish three papers that reported the isolation of the gene in 1993.¹⁶

Function of the Menkes protein in copper homeostasis

The full predicted amino acid sequence of the Menkes protein (initially called MNK but later renamed ATP7A), revealed it to be a P-type ATPase, with the unique property of having six putative metal-binding sites in its first 700 amino acids. As quickly as possible we expressed the metal-binding site region in E. coli and used the expressed protein to raise antibodies to the protein, so we could determine its intracellular location.

We were fortunate that Jim had developed a series of copper resistant CHO cell lines over the previous few years, and it was of great interest to use these to look at the expression of MNK (as it was still called) in these cells. The task was allotted to Mick Petris, who undertook this work as part of his undergraduate honours research project jointly supervised by Jim and Julian. This work revealed the fascinating conclusion that the cells acquired resistance to copper by amplifying the Menkes gene, and in this way they acquired an increased ability to efflux copper.⁸ This result indicated that the Menkes protein was a copper efflux protein, which fitted with its membership of the P-type ATPase family and the Menkes cultured cells phenotype. Mick then undertook a PhD, again jointly supervised by Jim and Julian, to study the function of ATP7A and its localisation in the cell. This work led to the exciting discovery of Cu-responsive trafficking of ATP7A and thus an explanation of how the one protein could provide copper to secreted cuproenzymes such as lysyl oxidase as well as efflux copper from the cell. Cu-responsive trafficking of ATP7A was identified as a key copper homeostatic mechanism.¹⁷ The discovery of Cu-responsive trafficking of ATP7A was seminal and metal-responsive trafficking of various metal transporters in various organisms has since been reported.

Molecular studies of trafficking mechanisms

The decade following the isolation of ATP7A was an exciting time of discoveries made possible by the new molecular tools available. Our laboratories made use of many of the tools and resources that we had built up over the years to identify details of how copper homeostasis was regulated and what goes wrong in MD.

An important advance was the construction of an expression vector allowing in vitro mutagenesis to be used to explore the functional amino acid regions of ATP7A. Initial attempts to clone the ATP7A cDNA in bacterial plasmids were frustrated by constant rearrangements; the only plasmids that were stable had mutations and deletions that prevented their use in mammalian expression systems. This problem was solved by Sharon La Fontaine, who developed a low copy number plasmid that allowed the propagation of the entire ATP7A coding region in E. coli.¹⁸ This breakthrough allowed us to generate many mutant constructs and this led to identification of the importance of the metal binding regions 5 and 6 in trafficking¹⁹ and the di-leucine C-terminal retrieval signal.²⁰ Interestingly we found that many missense mutations prevented the normal copper-induced trafficking of ATP7A, a fact that was relevant to understanding the various phenotypes in Menkes disease. Dr Ilia Voskoboinik and Jim further investigated the role of the N-terminal metal binding sites of ATP7A by expression in yeast and concluded that these sites were important in sensing low copper but not in overall catalytic activity.²¹

Analysis and treatment of MD patients

One of our long-term aims, of course, was to find a treatment for Menkes disease. Previous attempts to treat this devastating disease were largely unsuccessful due to the fact that, even if the gut absorption block to copper was bypassed by intraperitoneal or intramuscular copper administration, by the time diagnosis was made usually a few months after birth, a critical, copper-dependent stage of brain development had passed and the treatment proved ineffective. In families with a history of the disorder, prenatal diagnosis was possible using radioactive copper efflux assays and, as described above, Jim's laboratory was instrumental in developing this assay. Nevertheless, the copper isotopes used in the assay were of such a short half-life that working with them at times became a nightmare.

With over 30 years of study of MD, David Danks had established a Southern Hemisphere reference centre for the disease and we had an extensive collection of cell lines from affected patients that were available for mutation detection. Our paper describing the gene isolation included a northern blot that showed that many of the MD patients had low or absent ATP7A mRNA.^16b Indeed subsequent analysis found many patients to have splice site abnormalities that prevented the production of normal ATP7A. We continued the identification of mutations that allowed the development of prenatal and carrier DNA diagnosis for the Menkes families in our registry.

Two particular patients were of special interest. The first was a patient who was one of the first successfully treated MD patients. He had two brothers who had died at an early age, so his mother was offered a prenatal test, but she wanted to try copper therapy if the test was positive. The baby was induced at 35 weeks to allow treatment to start at an early age. The treatment was successful and he survived to age 16, but developed symptoms of occipital horn syndrome, a milder variant of MD.²² The other patient was described as a mild Menkes case.²³ He had many symptoms of the classical disease, but did not have as severe neurological impairment and did not display connective tissue abnormalities. Our mutation analysis discovered that the initial patient had a single nucleotide duplication in exon 22 which led to a frame shift and truncation of the protein, so that its normal C-terminus was lost, including the important di-leucine signal.²⁴ Work by Mick Petris has shown that when this signal is ablated the protein cannot be retrieved on the plasma membrane.²⁵ The evidence suggested that the mutant protein was localized constitutively on the plasma membrane. A partially active ATP7A would explain the successful therapeutic response and the fact that no protein was found at the TGN explained why connective tissue defects were not corrected, as lysyl oxidase receives its copper at the TGN. The mild Menkes patient was found to have a missense mutation in transmembrane domain 7 of ATP7A. There were normal levels of ATP7A located at the TGN but the mutant protein did not traffic detectably in response to copper. The protein presumably was partially active in copper transport, and delivered copper to lysyl oxidase, hence no connective tissue abnormalities. These observations led to an explanation of the variant Menkes phenotypes, based on the intracellular trafficking and location defects.²⁶ But these and other studies indicated that for copper therapy to be effective, some partially active mutant ATP7A must be present.²⁷ Effective treatment for this terrible disease has yet to be established, however, current work on gene therapy approaches and novel copper complexes are showing promise.

Studies on ATP7B

Soon after the discovery of ATP7A, several groups who had been closing in on the Wilson disease gene were able to complete the isolation,²⁸ for both genes are very similar copper-ATPases. We became interested in examining the different physiological roles of the two proteins. Other groups had reported that ATP7B underwent copper-responsive trafficking from the TGN to an unidentified vesicular compartment.²⁹ We used immunogold electron microscopy to show that the protein trafficked to multivesicular bodies resembling late endosomes.³⁰ Work with cultured hepatocytes showed that these vesicles were clustered around the biliary canalicular membranes, where copper was presumably secreted by exocytosis.^29a,31

Thus copper-responsive trafficking of the Cu-ATPases provided a clear mechanism for physiological copper homeostasis. Work by Jim and Mark Greenough showed that ATP7A trafficked to the basolateral membrane in response to Cu elevation in polarized cells,³² however, ATP7B traffics towards the apical membrane.^29a,31 Thus these two closely related molecules have evolved distinct physiological functions based on different trafficking targets.

As noted above, David Danks had noted that the liver copper poisoned sheep had some similarities to that seen in patients with advanced Wilson disease. So it was natural for us to investigate sheep ATP7B to see if this species had some abnormal form of the protein which could explain the tendency of sheep to accumulate excess hepatic copper. A surprising result, found by PhD student Paul Lockhart, was that sheep have two different forms of ATP7B: one, a minor form, has an additional sequence at the N-terminus.³³ Both proteins could confer copper resistance to cells, and trafficked in response to copper, so it did not appear that there was a defect in ATP7B in sheep. However, subsequently some trafficking differences in the two ATP7B proteins have been found that could be related to the unusual copper homeostasis in sheep (Mercer, unpublished data). Further work is needed to follow up on these observations.

Mouse models of copper disorders

Models of Menkes disease

From the earliest days of the Danks laboratory investigation into copper disorders, mouse models have played an important role. As discussed above, mottled mouse mutants had been found by David Hunt to have similar copper defects to those seen in Menkes disease.⁷ Indeed our later analysis revealed mutations in Atp7a in three of the mottled mutants.³⁴ One particular mutant, brindled, appeared to be a close clinical homologue to classical MD and was used to develop copper strategies for copper treatment. Jim, together with students Jeff Mann and Marie Phillips, found that there was a critical developmental window prior to 10 days postnatal for the copper treatment to be successful.^6a The corrected mice survived relatively well compared with treated human patients. In subsequent work we found that the brindled mouse has a two amino acid deletion in Atp7a and normal amounts of protein, but we predicted the copper transport activity was much reduced.³⁵ Thus success of copper therapy was again dependent on the presence of a small amount of residual ATP7A copper transport activity. The brindled mice are still being used to develop novel treatment strategies. In Julian's laboratory, post-doctoral fellow Roxana Llanos and PhD student Bi-Xia Ke produced transgenic mice that overexpressed ATP7A, and showed that these mice had lower copper concentrations in some tissues consistent with the efflux role of ATP7A.³⁶ By crossing the transgenic mice with brindled and dappled mutants, the mutants could be rescued, demonstrating that gene therapy approaches were worth pursuing.³⁷ Curiously, due to random inactivation of the transgene, the corrected males had a mottled coat and resembled female heterozygotes.

The higher level of ATP7A in the transgenic mice allowed an examination of the effects of increased copper in the small intestine on the localization of ATP7A in enterocytes.³⁸ When copper was depleted ATP7A was tightly perinuclear. However when the intestine was perfused with copper salts the protein trafficked to vesicles in the vicinity of the basolateral surface, consistent with a role in efflux of copper into the circulation. This result demonstrated that trafficking of ATP7A in the enterocytes was a physiological response to changes in copper in the diet, but that the response to excess copper was to pump it into the circulation, for distribution and disposal by the liver.

Models of Wilson disease

In 1983 Hal Rauch reported a mouse mutant he called “toxic milk” (tx), which not only had copper deficient milk causing the death of pups (like brindled), but if fostered onto normal dams the pups survived and then accumulated huge amounts of copper in their livers.³⁹ Thus these mice appeared be a good model of Wilson disease. We established a colony of these mice (with the help of Hal Rauch). Michael Theophilos in Julian's laboratory isolated the Atp7b cDNA from these mice, using information from the recently isolated Wilson disease gene (ATP7B) in humans. We found that the tx mice had a single missense mutation which affected a highly conserved methionine in transmembrane channel 8 and greatly reduced its copper transport activity.⁴⁰ Further work in collaboration with Leigh Ackland's group demonstrated that the ATP7A protein was present in the mammary gland of mice, but the localization and function of the protein was defective in the mutant animal, showing that ATP7A was important for supplying copper to breast milk.⁴¹ The phenotype of the tx mouse is less severe than the complete Atp7b knock out model, which was produced in Svetlana Lutsenko's laboratory,⁴² and so may prove to be a useful model for treatment studies.⁴³

Copper in neurological disorders

Although the severe neurological disorders in Menkes disease and the neurological changes in Wilson disease suggested that copper was important to normal brain development and function, these observations were not considered to be particularly interesting outside the immediate copper community. After all, these are rare conditions, and not therefore of much medical importance!

More recent findings, however, are changing this perception, and it is becoming clear that copper is playing a fundamental role in neuronal function, and that abnormal copper homeostasis is apparent in a number of important common diseases such as Alzheimer's, Parkinson's and motor neurone diseases. The exact nature of copper's role in these diseases is frustratingly difficult to unravel, but much interesting work is underway, some of which appears in this volume.

Our first introduction into the world of Alzheimer's disease (AD) and copper was in some collaborative work with Tony White and colleagues that showed increased copper levels in the cerebral cortex of mouse models of AD.⁴⁴ Amyloid Precursor Protein (APP) can be cleaved in a non-amyloidogenic way or via an amyloidogenic pathway to yield beta amyloid, which is believed to have a major role in the pathology of Alzheimer's disease. As APP was shown to be a copper-binding protein, this raised the possibility that abnormal copper homeostasis could be involved in development of disease pathology. This work is still ongoing!

Jim, together with post-doctoral fellow Dr Karla Acevedo, discovered copper-responsive trafficking of APP, a process with some similarities but also differences to Cu-responsive trafficking of ATP7A.⁴⁵ These studies supported a role for APP at the nerve synapse.

A major surprise came from work that Julian undertook with Marina Kennerson in Sydney. Marina had mapped a familial peripheral neuropathy to the ATP7A locus and had identified two missense mutations in conserved amino acids that were in an apparently functionally unimportant region of the protein.⁴⁶ In collaboration with Steve Kaler's laboratory we demonstrated trafficking defects in the mutant ATP7A.⁴⁷ A possible pathogenic mechanism is that copper is incorrectly released into the synaptic space, and this leads to axonal degeneration. A mouse model of one of the mutants has been produced and some details of its phenotype are published in this volume (Perez-Siles et al., DOI: 10.1039/C6MT00082G).

The role of copper in the brain and in neurodegenerative diseases is being actively investigated by Prof. Ashley Bush and colleagues (including several ex PhD students from Jim's lab) at the Florey Institute of Neuroscience and Mental Health in Melbourne. Julian is collaborating with Kay Double to investigate the role of copper in Parkinson's disease⁴⁸ and map copper transporters in the human brain.⁴⁹ So copper research continues to be alive and well in Melbourne! Even more than 40 years after David Danks first made the link between copper deficiency and the severe neurological defects in Menkes disease, the exact role of copper in neurological disorders remains elusive. But given the huge and growing number of people affected with these disorders, this field of research is one of the most exciting parts of the copper story.

The discoveries that demonstrate the importance of copper in many human disorders vindicates David Danks's insistence in pursuing studies of the rare “experiments of nature”. This research direction has opened the way to the modern understanding of how copper is handled in the body and what goes wrong in many different disorders. This should lead to rational approaches for therapy of several common neurological diseases.⁵⁰

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