RESUMO
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.
Assuntos
Cistatina M/genética , Epiderme/crescimento & desenvolvimento , Lentivirus/genética , Morfogênese/genética , RNA Interferente Pequeno/genética , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Cistatina M/fisiologia , Células Epidérmicas , Epiderme/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Humanos , Ictiose/patologia , Modelos Biológicos , Morfogênese/efeitos dos fármacos , Fenótipo , RNA Interferente Pequeno/farmacologia , Pele Artificial , Alicerces TeciduaisRESUMO
Cystatin M/E is a member of a superfamily of evolutionarily-related cysteine protease inhibitors that provide regulatory and protective functions against uncontrolled proteolysis by cysteine proteases. Although most cystatins are ubiquitously expressed, high levels of cystatin M/E expression are mainly restricted to the epithelia of the skin (epidermis, hair follicles, sebaceous glands, and sweat glands) and to a few extracutaneous tissues. The identification of its physiological targets and the localization of these proteases in skin have suggested a regulatory role for cystatin M/E in epidermal differentiation. In vitro biochemical approaches as well as the use of in vivo mouse models have revealed that cystatin M/E is a key molecule in a biochemical pathway that controls skin barrier formation by the regulation of both crosslinking and desquamation of the stratum corneum. Cystatin M/E directly controls the activity of cathepsin V, cathepsin L, and legumain, thereby regulating the processing of transglutaminases. Misregulation of this pathway by unrestrained protease activity, as seen in cystatin M/E-deficient mice, leads to abnormal stratum corneum and hair follicle formation, as well as to severe disturbance of skin barrier function. Here, we review the current knowledge on cystatin M/E in skin barrier formation and its potential role as a tumor suppressor gene.