Browsing by Subject "Keratins"

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    Human keratinocytes cultured without a feeder layer undergo progressive loss of differentiation markers
    (Murcia : F. Hernández, 1999) Prignano, F.; Domenici Lombardo, L.; Gerlini, G.; Pimpinelli, N.; Romagnoli, P.
    Culture of keratinocytes in conventional medium without a mesenchyme-derived feeder layer leads to poor growth and impaired differentiation; however, the exact pathway and degree of differentiation achieved in such conditions is unclear. We have cultured normal human keratinocytes in Rheinwald and Green's medium, on plastic without a feeder layer, in order to investigate the degree of differentiation that they achieve in these conditions. Intermediate filament proteins, tonofibrils and desmosomes were assumed as markers of differentiation and their expression was analyzed by immunohistochemistry and electron micros~opy. Before reaching confluence, keratinocytes expressed keratin molecules, as well as vimentin, and formed tonofibrils and desmosomes. The expression of these markers was progressively reduced until confluence and was totally lost thereafter, while cultures could be propagated for at least six passages. On the contrary, reseeding on a feeder layer after the first passage led to rapid cell death. It could be concluded that signals from a feeder layer are relevant to support continuous synthesis of intermediate filaments proteins and formation of tonofibils and desmosomes, and that the derangement of the cytoskeleton in these conditions leads to altered, not simply defective, response to delayed stimulation by a feeder layer.
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    Lessons from disorders of epidermal differentiation-associated keratins
    (Murcia : F. Hernández, 2002) Ishida-Yamamoto, A.; Takahashi, H.; lizuka, H.
    A number of diseases have been associated with mutations in genes encoding keratin intermediate filaments. Several of these disorders have skin manifestations, in which histological changes highlight the role of various different keratins in epidermal d i fferentiation. For example, mutations in either K1 or K10 (the major keratin pair expressed in diff e r e n t i a t e d keratinocytes) usually lead to clumped keratin filaments and cytolysis. Furthermore, the precise nature of the mutation has direct implications for disease phenotype. S p e c i f i c a l l y, mutations in the H1 and alpha-helical rod domains of K1/K10 result in bullous congenital ichthyosiform erythroderma, underscoring the critical role for this keratin filament domain in maintaining cellular integrity. However, a lysine to isoleucine substitution in the V1 domain of K1 underlies a form of palmoplantar keratoderma, which has different cell biological implications. Keratins are cross-linked into the cornified cell envelopes through this particular lysine residue and the consequences of the mutation lead to changes in keratin-desmosome association and cornified cell morphology, suggesting a role for this keratin subdomain in cornified cell envelope formation. Recently, to extend genotype-phenotype correlation, a frameshift mutation in the V2 region of the K1 tail domain was identified in ichthyosis hystrix (Curth-Macklin type), in which keratin filaments show a characteristic shell-like structure and fail to form proper bundles. In this case, the association of desmosomes with loricrin was also altered, implicating this keratin domain in organizing the intracellular distribution of loricrin during cornification. C o l l e c t i v e l y, these mutations in K1/K10 provide a fascinating insight into both normal and abnormal processes of epidermal differentiation.