A method is reported for the isolation of desmosomes in a high yield and of a purity suitable for biochemical analysis. The procedure utilizes the selective solubilizing action of citric acid-sodium citrate (CASC) buffer, pH 2.6, on the noncornified layers of cow nose epidermis, followed by discontinuous sucrose density gradient centrifugation. Electron microscopy with both thin sections of pellets and unfixed spread preparations reveals that after centrifugation, desmosomes are located mainly at the 55-60% sucrose interface. In the desmosome preparation thus obtained, the characteristic desmosome structure is well preserved, showing the midline, unit membranes, and dense plaques. Furthermore, removal of the epidermal filament bundles by the solubilizing action of CASC buffer has revealed a finely filamentous layer on the cytoplasmic surface of the plaques. The dimensions, location, and appearance of this layer correspond with those of the "connecting component" which has been previously suggested as being responsible for the attachment of epidermal filament bundles to the desmosome.

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Desmosomes, isolated from cow nose epidermis by a method utilizing citrate buffer pH 2.6 and density gradient centrifugation, have been analyzed and found to contain approximately 76% protein, t7% carbohydrate, and 10% lipid. Nonpolar amino acids predominate in desmosomal protein, representing 456 residues per 1,000. The sialic acid content is 5 n M / m g of protein.The lipid fraction is composed of approximately 40% cholesterol and 60% phospholipids.Desmosomes are completely solubilized by incubation with 2% sodium dodecyl sulphate and 1% /5-mercaptoethanol. Gel electrophoresis of the denatured desmosomal proteins reveals 24 bands, with mobilities corresponding to a molecular weight range of 15,000-230,000 daltons. Seven of these are considered to be major bands, together constituting 81% of the desmosomal protein. Bands 1 and 2, of molecular weights 230,000 and 210,000 daltons, together comprise 28% by weight of the desmosome. It is suggested that these protein chains are located in the desmosomal plaque. Bands 3 and 4 are PAS-positive, constitute 23% of the desmosomal protein, and have apparent molecular weights of 140,000 and 120,000 daltons, respectively. At least part of this material must originate from the carbohydrate-containing layer which is demonstrated, by histochemistry, to be present in the desmosomal interspace. The possible nature and origin of the remaining major bands, of molecular weights 90,000, 75,000, and 60,000 daltons, are discussed.

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A female infant born to a mother who had an elevated serum alpha-fetoprotein during early pregnancy, presented a combination of epidermolysis bullosa and aplasia cutis congenita. She developed evidence of upper gastrointestinal obstruction and died at the age of 43 hours. Post-mortem examination showed the presence of pyloric atresia and electron microscopy of skin biopsies showed epidermolysis bullosa simplex. Examination of the placenta revealed a unique abnormality of the membranes, indicating the existence of two sacs. This case and the previously reported cases, which are reviewed, suggest an autosomal recessive inheritance. Serum alphafetoprotein estimation, ultrasonography and fetoscopy with skin biopsy are suggested as a means of pre-natal diagnosis in future pregnancies.