To identify novel psoriasis-associated genes, we focused on several ESTs (expressed sequence tags) whose expression was predominantly increased in the affected skin in patients with psoriasis vulgaris, as assessed by microarray assay. In this paper, a full-length cDNA corresponding to one of those ESTs (AI440266) was isolated by screening of cultured human keratinocyte cDNA libraries. This cDNA has an open reading frame of a 309-amino-acid protein, sharing significant homology to one of the short-chain alcohol dehydrogenase/reductase (SDR) families that can catalyze the first and rate-limiting step that generates retinaldehyde from retinol. So, this gene was designated as hRDH-E2 (human epidermal retinal dehydrogenase 2). The hRDH-E2 gene has a single functional copy on chromosome 8q12.1, spanning approximately 20 kb with seven exons. The deduced amino acid sequence contains three motifs that are conserved in the SDR family. Qualitative RT-PCR demonstrated that the mRNA levels of hRDH-E2 were significantly elevated in the affected skin in psoriasis patients as compared to the unaffected skin in patients and the normal skin in healthy individual. These results suggest that hRDH-E2 may be involved in the pathogenesis of psoriasis through its critical role in retinol metabolism in keratinocyte proliferation. (C) 2002 Elsevier Science (USA). All rights reserved.