The keratin gene family is a large group of intermediate filament and structural proteins that provide the structural components of hair, nails, horns, scales, claws and similar types of hard tissues. Keratins are also important for intracellular stability in epithelial tissues and different keratins often display organ- or tissue specific expression patterns. Due to these specific expression patterns, keratins are often used as diagnostic biomarkers. Keratin 19 is a type I keratin and expressed in simple epithelia including glandular cell types present in the GI-tract, female tissues, male tissues, and respiratory epithelium. Clinically, keratin 19 is used together with keratin 18 to distinguish hepatocellular cancer from cholangiocellular carcinoma (both keratins are expressed in bile ducts, but keratin 18 is expressed in hepatocytes whereas keratin 19 is not). Keratin 19 is a type I keratin. The type I cytokeratins consist of acidic proteins which are arranged in pairs of heterotypic keratin chains. Unlike its related family members, this smallest known acidic cytokeratin is not paired with a basic cytokeratin in epithelial cells. It is specifically found in the periderm, the transiently superficial layer that envelops the developing epidermis. The type I cytokeratins are clustered in a region of chromosome 17q12-q21.
Background References
1. Stone M.R.et.al.Specific interaction of the actin-binding domain of dystrophin with intermediate filaments containing keratin 19.Mol. Biol. Cell 16:4280-4293(2005).
Sequence Similarity
Belongs to the intermediate filament family.
Tissue Specificity
Expressed in a defined zone of basal keratinocytes in the deep outer root sheath of hair follicles. Also observed in sweat gland and mammary gland ductal and secretory cells, bile ducts, gastrointestinal tract, bladder urothelium, oral epithelia, esophagus, ectocervical epithelium (at protein level). Expressed in epidermal basal cells, in nipple epidermis and a defined region of the hair follicle. Also seen in a subset of vascular wall cells in both the veins and artery of human umbilical cord, and in umbilical cord vascular smooth muscle. Observed in muscle fibers accumulating in the costameres of myoplasm at the sarcolemma in structures that contain dystrophin and spectrin.
Western blot analysis of Cytokeratin 19 on different lysates with Mouse anti-Cytokeratin 19 antibody (EM1901-76) at 1/1,000 dilution.
Lane 1: HCT 116-si NT cell lysate Lane 2: HCT 116-si Cytokeratin 19 cell lysate
Lysates/proteins at 10 µg/Lane.
Predicted band size: 44 kDa Observed band size: 40/44 kDa
Exposure time: 20 seconds; ECL: K1801;
4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (EM1901-76) at 1/1,000 dilution was used in 5% NFDM/TBST at 4℃ overnight. Goat Anti-Mouse IgG - HRP Secondary Antibody (HA1006) at 1/50,000 dilution was used for 1 hour at room temperature.
ICC staining of Cytokeratin 19 in JAR cells (green). Formalin fixed cells were permeabilized with 0.1% Triton X-100 in TBS for 10 minutes at room temperature and blocked with 1% Blocker BSA for 15 minutes at room temperature. Cells were probed with the primary antibody (EM1901-76, 1/50) for 1 hour at room temperature, washed with PBS. Alexa Fluor®488 Goat anti-Mouse IgG was used as the secondary antibody at 1/1,000 dilution. The nuclear counter stain is DAPI (blue).
Immunohistochemical analysis of paraffin-embedded human pancreas tissue using anti-Cytokeratin 19 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (EM1901-76, 1/1,000) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded human colon cancer tissue using anti-Cytokeratin 19 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (EM1901-76, 1/1,000) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded human breast tissue using anti-Cytokeratin 19 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (EM1901-76, 1/1,000) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded human small intestine tissue using anti-Cytokeratin 19 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (EM1901-76, 1/1,000) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Flow cytometric analysis of Cytokeratin 19 was done on MCF-7 cells. The cells were fixed, permeabilized and stained with the primary antibody (EM1901-76, 1/100) (red). After incubation of the primary antibody at room temperature for an hour, the cells were stained with a Alexa Fluor 488 Goat anti-Mouse IgG Secondary antibody at 1/500 dilution for 30 minutes.Unlabelled sample was used as a control (cells without incubation with primary antibody; black).
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