Characterization and expression analysis of the Spink5 gene, the mouse ortholog of the defective gene in Netherton syndrome.

The human SPINK5 gene, encoding the putative 15-domain serine protease inhibitor LEKTI, was identified as the defective gene in the severe autosomal recessive ichthyosiform skin disorder known as Netherton syndrome and as a candidate susceptibility gene for atopic disease. Here we report mapping of the murine Spink5 gene to chromosome 18 and its characterization. We show that, unlike in humans, transcription of the mouse Spink5 gene generates two mRNAs that differ in the 3' untranslated region. The encoded protein, which is detected in differentiated primary cultured keratinocytes and mouse skin as an approximately 130-kDa glycosylated precursor, displays approximately 60% identity with its human counterpart but lacks the human LEKTI domain 6. As in the human, mouse Lekti represents a marker of epithelial differentiation, strongly expressed in the granular layer of the epidermis, in suprabasal layers of stratified epithelia, and in thymic Hassall's bodies. Our data indicate that mouse Spink5/Lekti, like its human counterpart, is involved in the control of epithelial tissue homeostasis, but also highlight specific features of the murine gene and protein.