Keratin 6A

Keratin 6A is one of the 27 different type II keratins expressed in humans. Keratin 6A was the first type II keratin sequence determined. Analysis of the sequence of this keratin together with that of the first type I keratin led to the discovery of the four helical domains in the central rod of keratins. In humans Keratin 6A is encoded by the KRT6A is_associated_with::gene.

Keratins
is_associated_with::Keratins are the is_associated_with::intermediate filament proteins that form a dense meshwork of filaments throughout the is_associated_with::cytoplasm of is_associated_with::epithelial cells. Keratins form heterois_associated_with::polymers 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 is_associated_with::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 is_associated_with::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 is_associated_with::sulfur-containing is_associated_with::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 is_associated_with::chromosome 17q, whereas the genes for type II keratins are located in a cluster on human is_associated_with::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 cytois_associated_with::keratin, one of a number of is_associated_with::isoforms of is_associated_with::keratin 6 encoded by separate genes located within the type II keratin gene cluster on human is_associated_with::chromosome 12q. It is found with is_associated_with::keratin 16 and/or is_associated_with::keratin 17 in the palm and sole epidermis, the epithelial cells of the nail bed, the is_associated_with::filiform papillae of the is_associated_with::tongue, the is_associated_with::epithelial lining of oral is_associated_with::mucosa and is_associated_with::esophagus, as well as the is_associated_with::hair follicles. This keratin 6 isoform is thought to be the most abundant of the K6 isoforms.

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

Genetic disorders
Mutations in the genes expressing this protein have been associated with the PC1 variant of is_associated_with::pachyonychia congenita, an inherited disorder of the is_associated_with::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 is_associated_with::epithelia.