Keratin 6A: Difference between revisions

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{{Orphan|date=November 2006}}  
{{Infobox_gene}}
{{protein
'''Keratin 6A''' is one of the 27 different type II keratins expressed in humans. '''Keratin 6A''' was the first type II keratin sequence determined.<ref name="pmid6191871">{{Cite journal  | last1 = Hanukoglu | first1 = I. | last2 = Fuchs | first2 = E. | title = The cDNA sequence of a Type II cytoskeletal keratin reveals constant and variable structural domains among keratins. | journal = Cell | volume = 33 | issue = 3 | pages = 915–24 |date=Jul 1983 | doi =10.1016/0092-8674(83)90034-X  | PMID = 6191871 }}</ref> 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.<ref name="pmid6191871" /> In humans Keratin 6A is encoded by the ''KRT6A'' [[gene]].<ref name="pmid1713141">{{cite journal |vauthors=Rosenberg M, Fuchs E, Le Beau MM, Eddy RL, Shows TB | title = Three epidermal and one simple epithelial type II keratin genes map to human chromosome 12 | journal = Cytogenet. Cell Genet. | volume = 57 | issue = 1 | pages = 33–8 | year = 1991 | pmid = 1713141 | doi = 10.1159/000133109| url =  }}</ref><ref name="pmid16831889">{{cite journal |vauthors=Schweizer J, Bowden PE, Coulombe PA, Langbein L, Lane EB, Magin TM, Maltais L, Omary MB, Parry DA, Rogers MA, Wright MW | title = New consensus nomenclature for mammalian keratins | journal = J. Cell Biol. | volume = 174 | issue = 2 | pages = 169–74 |date=July 2006 | pmid = 16831889 | pmc = 2064177 | doi = 10.1083/jcb.200603161 | url = }}</ref>
| Name = keratin 6A
| caption =  
| image =  
| 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 ==


[[Keratins]] are the [[intermediate filament]] proteins that form a dense meshwork of filaments throughout the [[cytoplasm]] of [[epithelial]] cells. Keratins form hetero[[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 [[cellular differentiation]]-specific manner.
[[Keratins]] are the [[intermediate filament]] proteins that form a dense meshwork of filaments throughout the [[cytoplasm]] of [[epithelial]] cells. Keratins form hetero[[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 (biology)|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 (anatomy)|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.
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 (anatomy)|nail]] are known as "hard keratins" or "[[Trichocyte (human)|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).
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 17]]q, whereas the genes for type II keratins are located in a cluster on human [[chromosome 12]]q (the exception being K18, a type I keratin located in the type II gene cluster).


== Keratin 6A ==
== Keratin 6A ==


'''Keratin 6A''' (protein name K6A; gene name ''KRT6A''), is a type II cyto[[keratin]], one of a number of [[isoform]]s 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 follicle]]s. This keratin 6 isoform is thought to be the most abundant of the K6 isoforms.
'''Keratin 6A''' (protein name K6A; gene name ''KRT6A''), is a type II cyto[[keratin]], one of a number of [[isoform]]s of [[keratin 6]] encoded by separate genes located within the type II keratin gene cluster on human [[chromosome 12]]q. 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 follicle]]s. 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.
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.
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== Genetic disorders ==
== 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]] <ref>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].</ref><ref>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].</ref><ref>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].</ref>.
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 (skin)|epidermis]] of the palms and soles, and oral [[epithelia]].<ref name="pmid7539673">{{cite journal |vauthors=McLean WH, Rugg EL, Lunny DP, Morley SM, Lane EB, Swensson O, Dopping-Hepenstal PJ, Griffiths WA, Eady RA, Higgins C | title = Keratin 16 and keratin 17 mutations cause pachyonychia congenita | journal = Nat. Genet. | volume = 9 | issue = 3 | pages = 273–8 |date=March 1995 | pmid = 7539673 | doi = 10.1038/ng0395-273 | url = }}</ref><ref name="pmid7545493">{{cite journal |vauthors=Bowden PE, Haley JL, Kansky A, Rothnagel JA, Jones DO, Turner RJ | title = Mutation of a type II keratin gene (K6a) in pachyonychia congenita | journal = Nat. Genet. | volume = 10 | issue = 3 | pages = 363–5 |date=July 1995 | pmid = 7545493 | doi = 10.1038/ng0795-363 | url = }}</ref><ref name="pmid9618173">{{cite journal |vauthors=Smith FJ, Jonkman MF, van Goor H, Coleman CM, Covello SP, Uitto J, McLean WH | title = A mutation in human keratin K6b produces a phenocopy of the K17 disorder pachyonychia congenita type 2 | journal = Hum. Mol. Genet. | volume = 7 | issue = 7 | pages = 1143–8 |date=July 1998 | pmid = 9618173 | doi = 10.1093/hmg/7.7.1143| url =  }}</ref>
 
==External links==
* [https://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=pc  GeneReviews/NCBI/NIH/UW entry on Pachyonychia Congenita]


==References==
==References==
{{reflist}}


{{reflist|2}}
{{Cytoskeletal proteins}}
 
{{Fibrous proteins}}


[[Category:Keratins]]
[[Category:Keratins]]
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Keratin 6A is one of the 27 different type II keratins expressed in humans. Keratin 6A was the first type II keratin sequence determined.[1] 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.[1] In humans Keratin 6A is encoded by the KRT6A gene.[2][3]

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.[4][5][6]

External links

References

  1. ↑ 1.0 1.1 Hanukoglu, I.; Fuchs, E. (Jul 1983). "The cDNA sequence of a Type II cytoskeletal keratin reveals constant and variable structural domains among keratins". Cell. 33 (3): 915–24. doi:10.1016/0092-8674(83)90034-X. PMID 6191871.
  2. ↑ Rosenberg M, Fuchs E, Le Beau MM, Eddy RL, Shows TB (1991). "Three epidermal and one simple epithelial type II keratin genes map to human chromosome 12". Cytogenet. Cell Genet. 57 (1): 33–8. doi:10.1159/000133109. PMID 1713141.
  3. ↑ Schweizer J, Bowden PE, Coulombe PA, Langbein L, Lane EB, Magin TM, Maltais L, Omary MB, Parry DA, Rogers MA, Wright MW (July 2006). "New consensus nomenclature for mammalian keratins". J. Cell Biol. 174 (2): 169–74. doi:10.1083/jcb.200603161. PMC 2064177. PMID 16831889.
  4. ↑ McLean WH, Rugg EL, Lunny DP, Morley SM, Lane EB, Swensson O, Dopping-Hepenstal PJ, Griffiths WA, Eady RA, Higgins C (March 1995). "Keratin 16 and keratin 17 mutations cause pachyonychia congenita". Nat. Genet. 9 (3): 273–8. doi:10.1038/ng0395-273. PMID 7539673.
  5. ↑ Bowden PE, Haley JL, Kansky A, Rothnagel JA, Jones DO, Turner RJ (July 1995). "Mutation of a type II keratin gene (K6a) in pachyonychia congenita". Nat. Genet. 10 (3): 363–5. doi:10.1038/ng0795-363. PMID 7545493.
  6. ↑ Smith FJ, Jonkman MF, van Goor H, Coleman CM, Covello SP, Uitto J, McLean WH (July 1998). "A mutation in human keratin K6b produces a phenocopy of the K17 disorder pachyonychia congenita type 2". Hum. Mol. Genet. 7 (7): 1143–8. doi:10.1093/hmg/7.7.1143. PMID 9618173.
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