Keratin 7

Keratin, type II cytoskeletal 7 also known as cytokeratin-7 (CK-7) or keratin-7 (K7) or sarcolectin (SCL) is a protein that in humans is encoded by the KRT7 gene.^[5][6][7] Keratin 7 is a type II keratin. It is specifically expressed in the simple epithelia lining the cavities of the internal organs and in the gland ducts and blood vessels.

KRT7
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 4XIF
Identifiers
Aliases	KRT7, CK7, K2C7, K7, SCL, keratin 7
External IDs	OMIM: 148059; MGI: 96704; HomoloGene: 4058; GeneCards: KRT7; OMA:KRT7 - orthologs
Gene location (Human) Chr. Chromosome 12 (human)[1] Band 12q13.13 Start 52,232,520 bp[1] End 52,252,186 bp[1]
Gene location (Mouse) Chr. Chromosome 15 (mouse)[2] Band 15 F1- F2|15 56.88 cM Start 101,308,924 bp[2] End 101,328,194 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in left lobe of thyroid gland right lobe of thyroid gland olfactory zone of nasal mucosa upper lobe of left lung right lung islet of Langerhans right uterine tube gallbladder minor salivary glands placenta Top expressed in transitional epithelium of urinary bladder right lung lobe left lung left lung lobe crypt of lieberkuhn of small intestine conjunctival fornix submandibular gland cervix pyloric antrum efferent ductule More reference expression data BioGPS More reference expression data
Gene ontology Molecular function protein binding structural molecule activity Cellular component cytoplasm keratin filament extracellular exosome intermediate filament nucleus cytosol Biological process viral process keratinization cornification Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 3855 110310 Ensembl ENSG00000135480 ENSMUSG00000023039 UniProt P08729 Q9DCV7 RefSeq (mRNA) NM_005556 NM_033073 RefSeq (protein) NP_005547 NP_149064 Location (UCSC) Chr 12: 52.23 – 52.25 Mb Chr 15: 101.31 – 101.33 Mb PubMed search [3] [4]
Wikidata
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Function

Keratin-7 is a member of the keratin gene family. The type II cytokeratins consist of basic or neutral proteins which are arranged in pairs of heterotypic keratin chains coexpressed during differentiation of simple and stratified epithelial tissues. This type II cytokeratin is specifically expressed in the simple epithelia lining the cavities of the internal organs and in the gland ducts and blood vessels. The genes encoding the type II cytokeratins are clustered in a region of chromosome 12q12-q13. Alternative splicing may result in several transcript variants; however, not all variants have been fully described.^[7]

Keratin-7 is found in simple glandular epithelia, and in transitional epithelium. Epithelial cells of the lung and breast both contain keratin-7, but some other glandular epithelia, such as those of the colon and prostate, do not.

Immunohistochemistry

Immunohistochemistry for CK7 of a metastatic undifferentiated carcinoma to a lymph node.

Because the keratin-7 antigen is found in both healthy and neoplastic cells, antibodies to CK7 can be used in immunohistochemistry to distinguish ovarian and transitional cell carcinomas (staining positive) from colonic and prostate cancers (negative), respectively. It is commonly used together with CK20 when making such diagnoses.^[8]

CK7 and CK20 expression by various body locations.^[9]