ATP7A gene mutations in 16 patients with Menkes disease and a patient with occipital horn syndrome

Abstract

Genomic DNA of 17 unrelated Japanese males with Menkes disease and 2 Japanese males with occipital horn syndrome were studied for mutations in the ATP7A gene. Using SSCP analysis and direct sequencing of the exons and the 5'-upstream region of the gene amplified by PCR, we identified 16 mutations in 16 of 17 males with Menkes disease, including 4 deletions, 2 insertions, 6 nonsense mutations, 2 missense mutations, and 2 splice-site mutations. All these mutations were those that affect the function of the gene. Of the two males with occipital horn syndrome, one had a splice-site mutation in intron 6 that led to normal-size and smaller-size transcripts. The amount of the normal-size transcripts in his cultured skin fibroblasts was 19% of the normal level. His serum copper and ceruloplasmin levels were normal, whereas his cultured skin fibroblasts contained increased levels of copper. These findings indicate that his mild clinical manifestations were due to the presence of normal-size and presumably functional transcripts of the gene. DNA sequencing analysis of the exons and 5'-upstream region of the ATP7A gene in 20 normal individuals and the 19 affected males identified 25 polymorphisms.

Functional copper transport explains neurologic sparing in Occipital Horn syndrome

“…However, the identical mutation was reported in another patient with OHS, in whom quantitative RT-PCR of fibroblast mRNA showed 18% to 21% properly spliced transcripts compared with normal. 22 On the basis of these patients' neurologic phenotypes (each achieved independent walking between 3 and 4 years of age without early copper treatment) relative to classic Menkes disease, we suggest that the latter assessment is a more accurate prediction of residual copper transporter in vivo.…”

“…In two other patients with typical OHS, a deletion in the promoter region 23 and a frameshift mutation in the final exon 24 were associated with the phenotype. We and others 4,18,21,22 have speculated that the molecular defects underlying OHS allow production of some residual copper transport activity; however, functional copper transport was not assessed for any of these mutations, except for radiolabeled copper egress studies in cultured fibroblasts, an assay that does not quantitatively distinguish classic Menkes from mild Menkes or OHS. 4 In the first patient with typical OHS defined molecularly (S833G, located within the splice donor site of exon 11 and leading to skipping of exons 11 and/or 12 in some transcripts, as well as some properly spliced transcripts), 4,25 the level of correctly spliced transcripts was estimated as 36% of normal as measured by RNase protection.…”

A comparison of the mutation spectra of Menkes disease and Wilson disease

“…Indeed, with respect to ATP7A, mutations have been identified in patients with milder forms of MNK, including OHS and mild MNK. Eight OHS-causing variants have been identified in ATP7A, with seven of the eight resulting in aberrant splicing (Das et al 1994(Das et al , 1995Gu et al 2001;Kaler et al 1994;Møller et al 2000;Qi and Byers 1998;Ronce et al 1997). Four of the eight OHS patient mutations occur at splice-site junctions, two are missense mutations, one is a deletion of a guanine, and the other occurs in the regulatory region of the ATP7A gene (not plotted).…”

“…Over 200 disease-causing variants have been identified in MNK patients. A literature search was performed to assemble the various ATP7A mutations available (Ambrosini and Mercer 1999; Beck et al 1994;Chelly et al 1993;Dagenais et al 2001;Das et al 1994Das et al , 1995Gu et al 2001;Hahn et al 2001;Kaler et al 1994Kaler et al , 1995Kapur et al 1987;Levinson et al 1996;Mak et al 2002;Møller et al 2000;Ogawa et al 1999aOgawa et al , 1999bOgawa et al , 2000Ozawa et al 2001;Qi and Byers 1998;Ronce et al 1997;Tümer et al 1992Tümer et al , 1994bTümer et al , 1996Vulpe et al 1993). We accessed 87 MNK patient point mutations identified in ATP7A for use in our comparisons (see Table 1).…”

Menkes disease

“…To date about 170 different mutations (from single-amino-acid substitutions to large deletions and chromosome aberrations) affecting ATP7A have been reported [28][29][30][31][32] (Human Gene Mutation Database (HGMD); www.hgmd.org).…”