Jansen, P.A., van den Bogaard, E.H., Kersten, F.F., Oostendorp, C., van Vlijmen-Willems, I.M., Oji, V., Traupe, H., Hennies, Hans C., Schalkwijk, J. and Zeeuwen, P.L. (2012) Cystatin M/E knockdown by lentiviral delivery of shRNA impairs epidermal morphogenesis of human skin equivalents. Experimental dermatology, 21 (11). pp. 889-891. ISSN 1600-0625

The protease inhibitor cystatin M/E (CST6) regulates a biochemical pathway involved in stratum corneum homeostasis, and its deficiency in mice causes ichthyosis and neonatal lethality. Cystatin M/E deficiency has not been described in humans so far, and we did not detect disease-causing mutations in the CST6 gene in a large number of patients with autosomal recessive congenital ichthyosis, who were negative for mutations in known ichthyosis-associated genes. To investigate the phenotype of CST6 deficiency in human epidermis, we used lentiviral delivery of short hairpin RNAs that target CST6 in a 3D reconstructed skin model. Surprisingly, CST6 deficiency did not cause an ichthyosis-like phenotype, but prevented the development of a multilayered epidermis. From this study, we conclude that CST6 deficiency may be incompatible with normal human foetal development.