Menkes syndrome: subcellular distribution of copper determined by an ultrastructural histochemical technique

Orchestration of dynamic copper navigation – new and missing pieces

A general principle in all cells in the body is that an essential metal – here copper – is taken up at the plasma membrane, directed through cellular compartments for use in specific enzymes and pathways, stored in specific scavenging molecules if in surplus, and finally expelled from the cells.

Changes in body weight and height in survivors of Menkes disease

OBJECTIVE

To explore the changes in the body weight and height of Menkes disease (MNK) patients treated with long-term copper-histidine.

METHODS

A survey involving a retrospective review of medical records or summaries of MNK patients was conducted. Patients were 44 males born after 1994, and their feeding method and genetic analysis of the ATP7A gene were reviewed. We compared the data of body weight and height from birth until 6 years between classical MNK patients and the general population obtained from national data and between patients who received early treatment and patients who received late treatment.

RESULTS

Although five patients who received early treatment reached some developmental milestones, the body weight and height did not differ from patients who received late treatment in the mode of oral nutrition, and were lower in comparison to the national data (<3 percentile).

CONCLUSION

We reported changes in the body weight and height of MNK patients who received early and late treatment. Although early treatment with copper-histidine had favorable effects on neurological development, it did not result in improvements in body weight and height. We suggest that the establishment of sufficient nutritional support is necessary along with early parenteral copper treatment to improve whole body condition in MNK patients.

Copper-transporting ATPases ATP7A and ATP7B: cousins, not twins

Copper plays an essential role in human physiology and is indispensable for normal growth and development. Enzymes that are involved in connective tissue formation, neurotransmitter biosynthesis, iron transport, and others essential physiological processes require copper as a cofactor to mediate their reactions. The biosynthetic incorporation of copper into these enzymes takes places within the secretory pathway and is critically dependent on the activity of copper-transporting ATPases ATP7A or ATP7B. In addition, ATP7A and ATP7B regulate intracellular copper concentration by removing excess copper from the cell. These two transporters belong to the family of P(1)-type ATPases, share significant sequence similarity, utilize the same general mechanism for their function, and show partial colocalization in some cells. However, the distinct biochemical characteristics and dissimilar trafficking properties of ATP7A and ATP7B in cells, in which they are co-expressed, indicate that specific functions of these two copper-transporting ATPases are not identical. Immuno-detection studies in cells and tissues have begun to suggest specific roles for ATP7A and ATP7B. These experiments also revealed technical challenges associated with quantitative detection of copper-transporting ATPases in tissues, as illustrated here by comparing the results of ATP7A and ATP7B immunodetection in mouse cerebellum.

Functional and molecular responses of suckling rat pups and human intestinal Caco-2 cells to copper treatment

Ctr1 and Atp7A are copper (Cu) transporters that may play a role in the regulation of intestinal Cu absorption; however, intestinal regulation of these transporters by Cu in vivo has not been well defined. In this study, we hypothesized that Cu supplementation would alter the expression of intestine Ctr1 and Atp7A in vivo and further documented effects of Cu exposure on Cu transport, Ctr1 and Atp7A levels and localization in enterocyte-like Caco-2 cells. Suckling rat pups were supplemented with Cu (0 and 25 microg Cu/day) for 10 days and small intestine Cu concentration, Ctr1, Atp7A and metallothionein (MT) gene expression were measured by Northern blot analysis. Caco-2 cells were treated with basal medium, or medium supplemented with 3 and 94 microM CuSO4 and 67Cu transport, Ctr1 and Atp7A levels and localization were determined. In rat pups, Cu supplementation increased intestinal Cu, Ctr1 and MT gene expression; however, Atp7A gene expression was not significantly affected. Caco-2 cells treated with 94 microM Cu had lower cellular Cu uptake and export compared to untreated cells. While Ctr1 and Atp7A gene and protein levels were unaffected, confocal microscopy indicated that Ctr1 was endocytosed and co-localized with transferrin in Cu treated cells. This study demonstrates the functional response of intestinal cells to Cu treatment and suggests that both Ctr1 and Atp7A may regulate Cu absorption.

Experience with first trimester prenatal diagnosis of Menkes disease

We have performed 28 first trimester diagnoses for Menkes disease in 27 high risk pregnancies by direct copper measurement on chorionic villi (c.v.) Two male fetuses were found to be affected because of significantly increased copper content. In one male fetus a slightly increased copper content was observed indicating an exogenous copper contamination of the sample. This view was supported by normal results observed after abortion. Three out of 15 diagnostic c.v. samples with a female karyotype showed increased copper levels. In two of these cases, part of the copper content might have been released from the cannulae used for these particular biopsies. Histochemical visualization of copper accumulation in fixed chorionic villi of two affected fetuses and one female fetus was observed. [64Cu]-uptake studies have been performed on 11 diagnostic and 10 control c.v. samples. As the control samples in some cases were found to incorporate more [64Cu] than the corresponding diagnostic sample, this method cannot at present be used for diagnosis. Compiled results on newborn females gave evidence that two carriers expressed the paternal X-chromosome, and two carriers expressed the maternal X-chromosome in in chorionic villi.

A study of intestinal copper-binding proteins in mottled mice

The substantial retention of Cu2+ and to a lesser extent Zn2+, in the gut mucosa of neonatal MO mutant mice is largely associated with a low molecular weight protein tentatively identified as metallothionein. [35S]Cysteine incorporation into this protein in mutant mice is elevated, indicating that Cu2+ retention in the gut is associated with an increase in the synthesis of metallothionein. The high Cu2+ levels of mutant gut tissue decline rapidly with age to reach an approximately normal level by 24 days of age; this decline cannot be prevented by dietary supplementation and it is suggested that gut 'closure' and consequent reduced uptake by pinocytosis are important factors in this decline.

Menkes X-linked disease: prenatal diagnosis of hemizygous males and heterozygous females

Menkes X-linked disease, a copper disturbance syndrome, is detectable in cell cultures. Prenatal findings in two at-risk foetuses suggested that prenatal diagnosis was also feasible. In this study, we report substantial evidence that therapeutic abortion can be limited to hemizygous males. Forty-two at-risk pregnancies from 21 European families and 1 Canadian family were monitored with 64Cu-uptake into cultured amniotic fluid cells. In 10 pregnancies with a male karyotype an affected foetus was predicted on the basis of the copper studies. The pregnancies were terminated and the diagnosis was in each case confirmed by a markedly increased placenta copper content. Fourteen male foetuses were predicted to be unaffected and none of them has developed signs of Menkes disease after birth. In 6 of these cases the diagnosis was checked in the newborn boy by placenta copper measurements, and they all had copper concentrations within normal limits. Eighteen pregnancies with a female karyotype were also studied, 9 females could be identified as carriers on the basis of the tissue culture studies or raised placenta copper values.

Menkes X linked disease: two clonal cell populations in heterozygotes

The 64Cu incorporation into fibroblast clones obtained from three obligate and three suspected Menkes disease heterozygotes was studied. For each obligate heterozygote, two clonal cell populations were observed, one with a Menkes phenotype and one with a normal phenotype, as predicted by the Lyon hypothesis. The cloning results suggested a heterozygous state in two of the suspected carriers. The theoretical and practical limitation of the cloning method for identification of carriers of X linked diseases are discussed.

Menkes X linked disease: heterozygous phenotype in uncloned fibroblast cultures

The 64Cu incorporation into uncloned fibroblast cultures from 16 Menkes disease mothers and 19 first and second degree female relatives was examined. The mean incorporation for the Menkes disease mothers (36.2 +/- 3.6 SEM) differed significantly from that of 25 normal subjects (21.7 +/- 0.9 SEM) suggesting the presence of a significant proportion of mutant cells. In addition, the results suggested a heterozygous state in a number of the female relatives. Uncloned fibroblast cultures from four Menkes disease heterozygotes showed increasingly abnormal copper uptake values after repeated freezing procedures. Manipulation of tissue cultures may help to identify a number of female carriers.