Genomic localization, organization and amplification of the human zinc transporter protein gene, ZNT4, and exclusion as a candidate gene in different clinical variants of acrodermatitis enteropathica

Oliver Bleck, Gabrielle H. S. Ashton, Rajeev Mallipeddi, Andrew P. South, Neil V. Whittock, W. H. Irwin McLean, David J. Atherton, J. A. McGrath

Acrodermatitis enteropathica is an inherited disorder of zinc metabolism, the molecular basis of which is currently unknown. Recent transgenic mouse studies have highlighted the potential significance of certain zinc transport proteins, for example ZnT4, in providing clues to the pathogenesis of zinc-related disorders such as acrodermatitis enteropathica. Specifically, mice of any genotype suckled on ZnT4-deficient mice fail to absorb intestinal zinc and ZnT4-deficient mice also develop dermatitis, alopecia and stunted growth. Therefore, to assess human ZnT4 as a candidate gene/protein in acrodermatitis enteropathica or related disorders, we characterized the intron-exon organization of the human ZNT4 gene, which comprises seven distinct exons spanning approximately 38.7 kb. High-resolution radiation hybrid mapping placed ZNT4 on 15q21.1. We also developed a PCR-based mutation detection strategy using primers placed on flanking introns followed by direct sequencing of the PCR products. Using this approach, we sequenced DNA from five individuals with acrodermatitis enteropathica; no mutations were identified. Thus, ZNT4 is unlikely to be the correct candidate gene for this disorder. We also identified and characterized two common single nucleotide polymorphisms in exon 5 and in the 3' UTR of ZNT4, which will be useful for future genetic linkage studies in assessing ZNT4 as a candidate gene for other inherited disorders of zinc metabolism.