Partial Characterization of a Human ZincDeficiency Syndrome by Differential Display

The effect of the acrodermatitis enteropathica mutation (AE) on gene expression was investigated using differential display. Two differentially expressed cDNAs were partially characterized. The NA8 cDNA (HT₁₁A anchor and HAP 8 random primer pair) was expressed in greater quantity in normal fibroblasts, was 249 bp, and hybridized to three mRNA species (2 kb, 1 kb, 0.8 kb). Northern blot analysis indicated that the relative amounts of the AE mRNA species were reduced by 73%, 75%, and 52%, respectively. The cDNA sequence exhibited 92–93% homology to the human cytochrome oxidase subunit II, as analyzed through the GenBank database. The AEG4 cDNA species (HT₁₁G anchor and HAP 4 random, primer pair) was expressed in greater quantity in AE fibroblasts, was 197 bp, and hybridized to two mRNA species (9 kb, 4 kb). Northern blot analysis indicated that the 9-kb mRNA species was present equally in AE and normal cells, but the 4-kb mRNA species was only present in the AE fibroblasts. The cDNA sequence exhibited 92% homology to LINE1 human retrotransposons, as analyzed through the GenBank database. The functional relationship between the mutation and the reduced expression of cytochrome oxidase subunit II is unknown at this time and needs to be addressed. The increased expression of the LINE1 element in AE fibroblasts may be indicative of an insertion mutation affecting the mRNA of a protein involved in zinc transport, a prospect which requires further investigation.