Basal
keratins, suprabasal
keratins,
filaggrin, and cornified cell envelope (CCE) precursor
proteins are expressed during the differentiation of epidermal keratinocytes. These molecules are coordinately expressed during epidermal differentiation. The present study investigated the expression patterns of
keratins and CCE precursor
proteins in 15 patients with
epidermolysis bullosa simplex (EBS), which is caused by mutations in the genes that encode for the basal
keratins,
keratins 5 and 14. The patterns of expression of
keratins 5, 14, 1 and 10,
filaggrin, and of the three major CCE precursor
proteins,
involucrin,
loricrin and small
proline-rich
proteins 1 and 2 (
SPRs), were studied immunohistochemically and by electron microscopy. In 14 of the 15 patients with EBS, the distribution pattern of
keratins was not altered. In one neonate with EBS, basal cell
keratins were expressed in the suprabasal layers. Ultrastructurally, numerous clumped tonofilaments were observed in the basal and suprabasal cells. In all cases, findings were positive for
filaggrin in the granular cells, with positivity for
involucrin in the upper spinous and granular cells. The upper spinous cells and granular cells were positive for
SPRs 1 and 2, and
loricrin was expressed in granular cells. Ultrastructurally, no marked abnormality was observed in the suprabasal layers such as a decrease in, or agglutination of,
keratin filaments, except in one neonate. A CCE about 15 nm thick was formed normally in the cell membrane of cornified cells. The patterns of distributions of basal cell
keratins, suprabasal
keratins,
filaggrin, and CCE precursor
proteins, as well as the ultrastructural findings, resembled those of normal skin. Thus, the abnormality in basal cell
keratins in patients with EBS did not appear to alter the patterns of expression of the
keratins and CCE precursor
proteins.