Desmosomes differentiation

In skin, calcium can provide signals for the cells, either extracellular or intracellular (in the cytosol). The extra- and intracellular signaling may be connected to each other, but may also act separately. In cultured keratinocytes, extracellular calcium levels influence growth and differentiation.9,10 Low extracellular calcium levels (<0.1 mM) induce the growth of keratinocytes as a monolayer with a high proliferation rate, rapidly becoming confluent. In this condition keratinocytes never stratify, but possess many of the characteristics of basal cells the cells synthesize keratin proteins and are connected by occasional gap junctions but not by desmosomes. High extracellular calcium levels (>1 mM) induce differentiation of keratinocytes. Keratinocytes rapidly flatten, form desmosomes, and differentiate with stratification. Moreover, cornified envelopes form in cells of the uppermost layers.9,10... 

White, F.H. and Gohari, K., Some aspects of desmosomal morphology during differentiation of hamster cheek pouch, J. Submicrosc. Cytol., 16, 407, 1984. 

Skerrow, C.J., Clelland, D.G., and Skerow, D., Changes to desmosomal antigens and lectin-binding sites during differentiation in normal human epidermis a quantitative ultrastructural study,./. Cell Sci., 92, 667, 1989. 

Serre, G., Mils, V., Haftek, M., Vincent, C., Croute, F., Reano, A., Ouhayoun, J.-P., Bettinger, S., and Soleilhavoup, J.P., Identification of late differentiation antigens of human cornified epithelia, expressed in re-organized desmosomes and bound to cross-linked envelopes,. /. Invest. Dermatol., 97, 1061, 1991. 

Desmosomes and Filaments. The cohesiveness and internal structure of SC cells are dependent on the structures that are called desmosomes (25, 26, 27). These structures unite SC cells of different layers (Figure 3) and of the same layer (Figures 4 and 5). The sequence of embryonic development is a thickening of opposed cell membranes followed by intercellular disc formation and intracellular formation of the attachment plate (25, 29). This sequence is blocked if normal protein production in rough endoplasmic reticulum is altered by virus activity (28). When complete, the desmosomes of basal cells sprout filaments from their attachment plates (25, 27, 30). These filaments become longer, thicker, and more numerous as cells differentiate and migrate toward the skin surface (31, 32). Filaments arise either from the attachment plate (27) or they form loops that are anchored there (26). The smallest filaments... 

Moll R, Lee 1, Gould VE, et al. Immunocytochemical analysis of Ewing s tumors. Patterns of expression of intermediate filaments and desmosomal proteins indicate cell type heterogeneity and pluripotential differentiation. Am J Pathol. 1987 127 288-304. 

The epidermis Is a tough outer layer of tissue, which acts as a water-tight barrier to prevent desiccation and serves as a protection against abrasion. In epidermal cells, bundles of keratin filaments are cross-linked by filaggrin, an IFAP, and are anchored at their ends to desmosomes. As epidermal cells differentiate, the cells condense and die, but the keratin filaments remain intact, forming the structural core of the dead, keratinized layer of skin. The structural Integrity of keratin Is essential in order for this layer to withstand abrasion. 

Adenocarcinoma Pleural effusion MClO Tumorigenic, poorly differentiated microvilli, desmosomes... 

Cell-surface changes also accompany the effects of retinoids on epidermal cells. Christophers and Wolff (1975) using cultured epidermal cells derived from adult guinea pig ear skin fragments, showed that addition of retinoic acid (lO" M) increased the number of hemidesmosomes formed by the plasma membrane stratification and differentiation, on the other hand, is characterized by the formation of desmosomes. Hemidesmosome formation was acconipanied by decreased cell-cell adhesion and increased cell-substratum adhesion, as had been noted earlier by Yuspa and Harris (1974). 

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