The RNA tissue category is based on mRNA expression levels in the analyzed tissues (RNA assay description). The categories include: tissue enriched, group enriched, tissue enhanced, expressed in all, mixed and not detected. RNA tissue category is calculated separately both for internally generated Human Protein Atlas (HPA) RNA-seq data, as well as RNA-seq data from the Genotype-Tissue Expression (GTEx) project and CAGE data from FANTOM5 project.
Protein evidence scores are generated from several independent sources and are classified as evidence at i) protein level, ii) transcript level, iii) no evidence, or iv) not available.
Evidence at protein level
A summary of the overall protein expression pattern across the analyzed tissues. The summary is based on knowledge-based annotation.
"Estimation of protein expression could not be performed. View primary data." is shown for genes analyzed with a knowledge-based approach where available RNA-seq and gene/protein characterization data has been evaluated as not sufficient in combination with immunohistochemistry data to yield a reliable estimation of the protein expression profile.
Cytoplasmic expression in non-keratinized squamous epithelia and airway epithelia.
Data reliability descriptioni
Standardized explanatory sentences with additional information required for full understanding of the knowledge-based expression profile.
Antibody staining mainly consistent with RNA expression data. Presumed off target binding observed and disregarded.
Reliability score (score description), divided into Supported, Approved, or Uncertain, is based on consistency between the staining pattern of one antibody or several antibodies with RNA-seq data and available gene/protein characterization data.
Below is an overview of RNA and protein expression data generated in the Human Protein Atlas project. Analyzed tissues are divided into color-coded groups according to which functional features they have in common. For each group, a list of included tissues is accessed by clicking on group name, group symbol, RNA bar, or protein bar. Subsequent selection of a particular tissue in this list links to the image data page. Images of selected tissues give a visual summary of the protein expression profile furthest to the right. The gray human body provides links to a histology dictionary when clicking on any part of the figure.
RNA expression (TPM)i
RNA-seq results generated in HPA are reported as number of transcripts per million (TPM). Each bar represents the highest expression score found in a particular group of tissues. The assay is described more in detail in Assays & Annotation.
Protein expression (score)i
Each bar represents the highest expression score found in a particular group of tissues. Protein expression scores are based on a best estimate of the "true" protein expression from a knowledge-based annotation, described more in detail under Assays & annotation. For genes where more than one antibody has been used, a collective score is set displaying the estimated true protein expression.
Protein expression data is shown for each of the 44 tissues. The color-coding is based on tissues with functional features in common. Mouse-over function shows protein score for analyzed cell types found in a selected tissue. To access image data click on tissue name or bar. Annotation of protein expression is described in detail in Assays & annotation.
For genes with available protein data for which a knowledge-based annotation gave inconclusive results, no protein expression data is displayed in the protein expression data overview, however, all immunohistochemical images are still available and the annotation data can be found under Primary data.
RNA EXPRESSION OVERVIEWi
RNA expression overview shows RNA-data from three different sources: Internally generated Human Protein Atlas (HPA) RNA-seq data, RNA-seq data from the Genotype-Tissue Expression (GTEx) project and CAGE data from FANTOM5 project. Color-coding is based on tissue groups, each consisting of tissues with functional features in common. To access sample data, click on tissue name or bar.
HPA dataset RNA-seq tissue data is reported as mean TPM (transcripts per million), corresponding to mean values of the different individual samples from each tissue. Color-coding is based on tissue groups, each consisting of tissues with functional features in common. To access sample data, click on tissue name or bar. The RNA-seq assay is described in detail in Assays & Annotation.
RNA tissue category HPA HPA RNA tissue category (category description) is calculated based on mRNA expression levels across all tissues and include: tissue enriched, group enriched, tissue enhanced, expressed in all, mixed and not detected.
RNA tissue category: Tissue enriched (esophagus)
GTEx dataset RNA-seq data are reported as median RPKM (reads per kilobase per million mapped reads), generated by the Genotype-Tissue Expression (GTEx) project. More information can be found in Assays & Annotation.
RNA tissue category GTEx GTEx RNA tissue category (category description) is calculated based on mRNA expression levels across all tissues and include: tissue enriched, group enriched, tissue enhanced, expressed in all, mixed and not detected.
RNA tissue category: Tissue enhanced (esophagus)
FANTOM5 dataset Tissue data obtained through Cap Analysis of Gene Expression (CAGE) are reported as Tags Per Million, generated by the FANTOM5 project. More information can be found in Assays & Annotation.
RNA tissue category FANTOM5 FANTOM5 RNA tissue category (category description) is calculated based on gene expression levels across all tissues and include: tissue enriched, group enriched, tissue enhanced, expressed in all, mixed and not detected.
RNA tissue category: Group enriched (esophagus, tonsil)
Gene information from Ensembl and Entrez, as well as links to available gene identifiers are displayed here. Information was retrieved from Ensembl if not indicated otherwise.
KRT4 (HGNC Symbol)
CK4, CYK4, K4
Keratin 4, type II (HGNC Symbol)
Entrez gene summary
The protein encoded by this gene 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 differentiated layers of the mucosal and esophageal epithelia with family member KRT13. Mutations in these genes have been associated with White Sponge Nevus, characterized by oral, esophageal, and anal leukoplakia. The type II cytokeratins are clustered in a region of chromosome 12q12-q13. [provided by RefSeq, Jul 2008]
The protein browser displays the antigen location on the target protein(s) and the features of the target protein. The tabs at the top of the protein view section can be used to switch between the different splice variants to which an antigen has been mapped.
At the top of the view, the position of the antigen (identified by the corresponding HPA identifier) is shown as a green bar. A yellow triangle on the bar indicates a <100% sequence identity to the protein target.
Under the antigens, the maximum percent sequence identity of the protein to all other proteins from other human genes is displayed, using a sliding window of 10 aa residues (HsID 10) or 50 aa residues (HsID 50) (read more).
If a signal peptide is predicted by a majority of the signal peptide predictors SPOCTOPUS, SignalP 4.0, and Phobius (turquoise) and/or transmembrane regions (orange) are predicted by MDM, these are displayed.
Low complexity regions are shown in yellow and InterPro regions in green. Common (purple) and unique (grey) regions between different splice variants of the gene are also displayed (read more), and at the bottom of the protein view is the protein scale.
The protein information section displays alternative protein-coding transcripts (splice variants) encoded by this gene according to the Ensembl database.
The ENSP identifier links to the Ensembl website protein summary, while the ENST identifier links to the Ensembl website transcript summary for the selected splice variant. The data in the UniProt column can be expanded to show links to all matching UniProt identifiers for this protein.
The protein classes assigned to this protein are shown if expanding the data in the protein class column. Parent protein classes are in bold font and subclasses are listed under the parent class.
The Gene Ontology terms assigned to this protein are listed if expanding the Gene ontology column. The length of the protein (amino acid residues according to Ensembl), molecular mass (kDalton), predicted signal peptide (according to a majority of the signal peptide predictors SPOCTOPUS, SignalP 4.0, and Phobius) and the number of predicted transmembrane region(s) (according to MDM) are also reported.