Keratin 6A

protein
Name = keratin 6A
caption =


width =
HGNCid = 6443
Symbol = KRT6A
AltSymbols =
EntrezGene = 3853
OMIM = 148041
RefSeq = NM_005554
UniProt = P02538
PDB =
ECnumber =
Chromosome = 12
Arm = q
Band = 12
LocusSupplementaryData = -q21

Keratins

Keratins are the intermediate filament proteins that form a dense meshwork of filaments throughout the cytoplasm of epithelial cells. Keratins form heteropolymers consisting of a type I and a type II keratin. Keratins are generally expressed in particular pairs of type I and type II keratin proteins in a tissue-specific and cellular differentiation-specific manner.

The keratin proteins of epithelial tissues are commonly known as "keratins" or are sometimes referred to as "epithelial keratins" or "cytokeratins". The specialized keratins of hair and nail are known as "hard keratins" or "trichocyte keratins". Trichocytes are the specialized epithelial cells from which hair and nail are composed. Trichocyte keratins are similar in their gene and protein structure to keratins except that they are especially rich in the sulfur-containing amino acid cysteine, which facilitates chemical cross-linking of the assembled hard keratins to form a more structurally resilient material.

Both epithelial keratins and hard keratins can be further subdivided into type I (acidic) keratins and type II (neutral-basic) keratins. The genes for the type I keratins are located in a gene cluster on human chromosome 17q, whereas the genes for type II keratins are located in a cluster on human chromosome 12q (the exception being K18, a type I keratin located in the type II gene cluster).

Keratin 6A

Keratin 6A (protein name K6A; gene name "KRT6A"), is a type II cytokeratin, one of a number of isoforms of keratin 6 encoded by separate genes located within the type II keratin gene cluster on human chromosome 12q. It is found with keratin 16 and/or keratin 17 in the palm and sole epidermis, the epithelial cells of the nail bed, the filiform papillae of the tongue, the epithelial lining of oral mucosa and esophagus, as well as the hair follicles. This keratin 6 isoform is thought to be the most abundant of the K6 isoforms.

The "KRT6A" gene consists of 9 exons separated by 8 introns and is located in the type II keratin gene cluster on human "chromosome" 12q. Keratin 6B and keratin 6C are encoded by the neighbouring genes, which are identical in intron-exon organization to "KRT6A" and are more than 99% identical in their DNA coding sequences.

Genetic disorders

Mutations in the genes expressing this protein have been associated with the PC1 variant of pachyonychia congenita, an inherited disorder of the epithelial tissues in which keratin 6A is expressed, particularly leading to structural abnormalities of the nails, the epidermis of the palms and soles, and oral epithelia [McLean WHI et al. (1995) Keratin 16 and keratin 17 mutations cause pachyonychia congenita. Nature Genetics 9:273-278. Abstract available here [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7539673&query_hl=8&itool=pubmed_docsum] .] [Bowden PE et al. (1995) Mutation of a type II keratin gene (K6a) in pachyonychia congenita. Nature Genetics 10:363-365. Abstract available here [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=7545493&query_hl=10&itool=pubmed_docsum] .] [Smith FJD et al. (1998) A mutation in human keratin K6b produces a phenocopy of the K17 disorder pachyonychia congenita type 2. Human Molecular Genetics 7:1143-1148. Abstract available here [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=9618173&query_hl=12&itool=pubmed_docsum] .] .

References