Keratins: A class of fibrous proteins or scleroproteins that represents the principal constituent of EPIDERMIS; HAIR; NAILS; horny tissues, and the organic matrix of tooth ENAMEL. Two major conformational groups have been characterized, alpha-keratin, whose peptide backbone forms a coiled-coil alpha helical structure consisting of TYPE I KERATIN and a TYPE II KERATIN, and beta-keratin, whose backbone forms a zigzag or pleated sheet structure. alpha-Keratins have been classified into at least 20 subtypes. In addition multiple isoforms of subtypes have been found which may be due to GENE DUPLICATION.Keratins, Type II: A keratin subtype that includes keratins that are generally larger and less acidic that TYPE I KERATINS. Type II keratins combine with type I keratins to form keratin filaments.Keratins, Hair-Specific: Keratins that are specific for hard tissues such as HAIR; NAILS; and the filiform papillae of the TONGUE.Keratins, Type I: A keratin subtype that includes keratins that are generally smaller and more acidic that TYPE II KERATINS. Type I keratins combine with type II keratins to form keratin filaments.Keratin-8: A type II keratin found associated with KERATIN-18 in simple, or predominately single layered, internal epithelia.Intermediate Filaments: Cytoplasmic filaments intermediate in diameter (about 10 nanometers) between the microfilaments and the microtubules. They may be composed of any of a number of different proteins and form a ring around the cell nucleus.Keratin-14: A type I keratin that is found associated with the KERATIN-5 in the internal stratified EPITHELIUM. Mutations in the gene for keratin-14 are associated with EPIDERMOLYSIS BULLOSA SIMPLEX.Keratin-10: A type I keratin that is found associated with the KERATIN-1 in terminally differentiated epidermal cells such as those that form the stratum corneum. Mutations in the genes that encode keratin-10 have been associated with HYPERKERATOSIS, EPIDERMOLYTIC.Epidermolysis Bullosa Simplex: A form of epidermolysis bullosa characterized by serous bullae that heal without scarring. Mutations in the genes that encode KERATIN-5 and KERATIN-14 have been associated with several subtypes of epidermolysis bullosa simplex.Hyperkeratosis, Epidermolytic: A form of congenital ichthyosis inherited as an autosomal dominant trait and characterized by ERYTHRODERMA and severe hyperkeratosis. It is manifested at birth by blisters followed by the appearance of thickened, horny, verruciform scales over the entire body, but accentuated in flexural areas. Mutations in the genes that encode KERATIN-1 and KERATIN-10 have been associated with this disorder.Keratin-1: A type II keratin that is found associated with the KERATIN-10 in terminally differentiated epidermal cells such as those that form the stratum corneum. Mutations in the genes that encode keratin-1 have been associated with HYPERKERATOSIS, EPIDERMOLYTIC.Keratin-5: A type II keratin that is found associated with the KERATIN-14 in the internal stratified EPITHELIUM. Mutations in the gene for keratin-5 are associated with EPIDERMOLYSIS BULLOSA SIMPLEX.Epidermis: The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).Keratin-18: A type I keratin found associated with KERATIN-8 in simple, or predominately single layered, internal epithelia.Keratinocytes: Epidermal cells which synthesize keratin and undergo characteristic changes as they move upward from the basal layers of the epidermis to the cornified (horny) layer of the skin. Successive stages of differentiation of the keratinocytes forming the epidermal layers are basal cell, spinous or prickle cell, and the granular cell.Hair: A filament-like structure consisting of a shaft which projects to the surface of the SKIN from a root which is softer than the shaft and lodges in the cavity of a HAIR FOLLICLE. It is found on most surfaces of the body.Keratin-16: A type I keratin expressed in a variety of EPITHELIUM, including the ESOPHAGUS, the TONGUE, the HAIR FOLLICLE and NAILS. Keratin-16 is normally found associated with KERATIN-6. Mutations in the gene for keratin-6 have been associated with PACHYONYCHIA CONGENITA, TYPE 1.Intermediate Filament Proteins: Filaments 7-11 nm in diameter found in the cytoplasm of all cells. Many specific proteins belong to this group, e.g., desmin, vimentin, prekeratin, decamin, skeletin, neurofilin, neurofilament protein, and glial fibrillary acid protein.Keratoderma, Palmoplantar: Group of mostly hereditary disorders characterized by thickening of the palms and soles as a result of excessive keratin formation leading to hypertrophy of the stratum corneum (hyperkeratosis).Keratin-17: A type I keratin found associated with KERATIN-6 in rapidly proliferating squamous epithelial tissue. Mutations in the gene for keratin-17 have been associated with PACHYONYCHIA CONGENITA, TYPE 2.Skin: The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.Keratin-2: A type II keratin found expressed in the upper spinous layer of epidermal KERATINOCYTES. Mutations in genes that encode keratin-2A have been associated with ICHTHYOSIS BULLOSA OF SIEMENS.Keratin-13: A type I keratin that is found associated with the KERATIN-4 in the internal stratified EPITHELIUM. Defects in gene for keratin 13 cause HEREDITARY MUCOSAL LEUKOKERATOSIS.Epithelium: One or more layers of EPITHELIAL CELLS, supported by the basal lamina, which covers the inner or outer surfaces of the body.Hair Follicle: A tube-like invagination of the EPIDERMIS from which the hair shaft develops and into which SEBACEOUS GLANDS open. The hair follicle is lined by a cellular inner and outer root sheath of epidermal origin and is invested with a fibrous sheath derived from the dermis. (Stedman, 26th ed) Follicles of very long hairs extend into the subcutaneous layer of tissue under the SKIN.Hoof and Claw: Highly keratinized processes that are sharp and curved, or flat with pointed margins. They are found especially at the end of the limbs in certain animals.Keratin-15: A type I keratin found in the basal layer of the adult epidermis and in other stratified epithelia.Hair Diseases: Diseases affecting the orderly growth and persistence of hair.Keratin-6: A type II keratin found associated with KERATIN-16 or KERATIN-17 in rapidly proliferating squamous epithelial tissue. Mutations in gene for keratin-6A and keratin-6B have been associated with PACHYONYCHIA CONGENITA, TYPE 1 and PACHYONYCHIA CONGENITA, TYPE 2 respectively.Desmosomes: A type of junction that attaches one cell to its neighbor. One of a number of differentiated regions which occur, for example, where the cytoplasmic membranes of adjacent epithelial cells are closely apposed. It consists of a circular region of each membrane together with associated intracellular microfilaments and an intercellular material which may include, for example, mucopolysaccharides. (From Glick, Glossary of Biochemistry and Molecular Biology, 1990; Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Feathers: Flat keratinous structures found on the skin surface of birds. Feathers are made partly of a hollow shaft fringed with barbs. They constitute the plumage.Vimentin: An intermediate filament protein found in most differentiating cells, in cells grown in tissue culture, and in certain fully differentiated cells. Its insolubility suggests that it serves a structural function in the cytoplasm. MW 52,000.Pachyonychia Congenita: A group of inherited ectodermal dysplasias whose most prominent clinical feature is hypertrophic nail dystrophy resulting in PACHYONYCHIA. Several specific subtypes of pachyonychia congenita have been associated with mutations in genes that encode KERATINS.Keratin-12: A type I keratin that is found associated with the KERATIN-3 in the CORNEA and is regarded as a marker for corneal-type epithelial differentiation. Mutations in the gene for keratin-12 have been associated with MEESMANN CORNEAL EPITHELIAL DYSTROPHY.Dipodomys: A genus of the family Heteromyidae which contains 22 species. Their physiology is adapted for the conservation of water, and they seldom drink water. They are found in arid or desert habitats and travel by hopping on their hind limbs.Keratin-9: A type II keratin found predominantly expressed in the terminally differentiated EPIDERMIS of palms and soles. Mutations in the gene for keratin 9 are associated with KERATODERMA, PALMOPLANTAR, EPIDERMOLYTIC.Cytoskeleton: The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm.Desmoplakins: Desmoplakins are cytoskeletal linker proteins that anchor INTERMEDIATE FILAMENTS to the PLASMA MEMBRANE at DESMOSOMES.Keratoderma, Palmoplantar, Epidermolytic: An autosomal dominant hereditary skin disease characterized by epidermolytic hyperkeratosis that is strictly confined to the palms and soles. It has been associated with mutations in the gene that codes for KERATIN-9.Fluorescent Antibody Technique: Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Nail Diseases: Diseases of the nail plate and tissues surrounding it. The concept is limited to primates.Keratin-19: A type I keratin found associated with KERATIN-7 in ductal epithelia and gastrointestinal epithelia.Mallory Bodies: Cytoplasmic hyaline inclusions in HEPATOCYTES. They are associated with ALCOHOLIC STEATOHEPATITIS and non-alcoholic STEATOHEPATITIS, but are also present in benign and malignant hepatocellular neoplasms, and metabolic, toxic, and chronic cholestatic LIVER DISEASES.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Nails, Malformed: Deformities in nail structure or appearance, including hypertrophy, splitting, clubbing, furrowing, etc. Genetic diseases such as PACHYONYCHIA CONGENITA can result in malformed nails.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Corneal Dystrophy, Juvenile Epithelial of Meesmann: An autosomal dominant form of hereditary corneal dystrophy due to a defect in cornea-specific KERATIN formation. Mutations in the genes that encode KERATIN-3 and KERATIN-12 have been linked to this disorder.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Papilloma: A circumscribed benign epithelial tumor projecting from the surrounding surface; more precisely, a benign epithelial neoplasm consisting of villous or arborescent outgrowths of fibrovascular stroma covered by neoplastic cells. (Stedman, 25th ed)Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.beta-Keratins: Keratins that form into a beta-pleated sheet structure. They are principle constituents of the corneous material of the carapace and plastron of turtles, the epidermis of snakes and the feathers of birds.Wool: The hair of SHEEP or other animals that is used for weaving.Skin DiseasesGriseofulvin: An antifungal agent used in the treatment of TINEA infections.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.