Editing Melanocyte (section)

== Function ==
[[File:Blausen 0632 Melanocyte.png|thumb|Illustration of a melanocyte]]
[[File:Micrograph of melanocytes in the epidermis.jpg|thumb|Micrograph of melanocytes in the epidermis]]
Through a process called melanogenesis, melanocytes produce [[melanin]], which is a pigment found in the [[human skin|skin]], [[human eye|eye]]s, [[hair]], [[nasal cavity]], and [[inner ear]]. This melanogenesis leads to a long-lasting pigmentation, which is in contrast to the pigmentation that originates from oxidation of already-existing melanin.

There are both basal and activated levels of melanogenesis; in general, lighter-skinned people have low basal levels of melanogenesis. Exposure to UV-B radiation causes increased melanogenesis. The purpose of melanogenesis is to protect the [[Subcutaneous tissue|hypodermis]], the layer under the skin, from damage by UV radiation. The color of the melanin is black, allowing it to absorb a majority of the UV light and block it from passing through the epidermis.<ref name=Agar2005>
{{cite journal | vauthors = Agar N, Young AR | title = Melanogenesis: a photoprotective response to DNA damage? | journal = Mutation Research | volume = 571 | issue = 1–2 | pages = 121–32 | date = April 2005 | pmid = 15748643 | doi = 10.1016/j.mrfmmm.2004.11.016 | bibcode = 2005MRFMM.571..121A }}</ref>

Since the action spectrum of [[sunburn]] and melanogenesis are virtually identical, they are assumed to be induced by the same mechanism.<ref name=Parrish1982>
{{cite journal | vauthors = Parrish JA, Jaenicke KF, Anderson RR | title = Erythema and melanogenesis action spectra of normal human skin | journal = Photochemistry and Photobiology | volume = 36 | issue = 2 | pages = 187–91 | date = August 1982 | pmid = 7122713 | doi = 10.1111/j.1751-1097.1982.tb04362.x | s2cid = 38940583 }}</ref> The agreement of the action spectrum with the absorption spectrum of DNA points towards the formation of [[cyclobutane pyrimidine dimer]]s (CPDs) - [[direct DNA damage]].

Typically, between 1000 and 2000 melanocytes are found per square millimeter of skin or approximately 5% to 10% of the cells in the basal layer of epidermis. Although their size can vary, melanocytes are typically 7 μm in length.

Both lightly and darkly pigmented skin contain similar numbers of  melanocytes,<ref name="Tadokoro Yamaguchi Batzer Coelho 2005 pp. 1326–1332">{{cite journal |last1=Tadokoro |first1=Taketsugu |last2=Yamaguchi |first2=Yuji |last3=Batzer |first3=Jan |last4=Coelho |first4=Sergio G. |last5=Zmudzka |first5=Barbara Z. |last6=Miller |first6=Sharon A. |last7=Wolber |first7=Rainer |last8=Beer |first8=Janusz Z. |last9=Hearing |first9=Vincent J. |year=2005 |title=Mechanisms of Skin Tanning in Different Racial/Ethnic Groups in Response to Ultraviolet Radiation |journal=Journal of Investigative Dermatology |publisher=Elsevier BV |volume=124 |issue=6 |pages=1326–1332 |doi=10.1111/j.0022-202x.2005.23760.x |issn=0022-202X|doi-access=free |pmid=15955111 }}</ref> with difference in [[Human skin color|skin color]] due to differences the packing of [[eumelanin]] into the [[melanosome]]s of [[keratinocyte]]s: those in dark-toned skin are "packaged into peri-nuclear distributed, ellipsoid" melanosomes while those light-tone skin are "assembled into clustered small, circular melanosomes".<ref name="Greaves 2014 p. 20132955">{{cite journal |last=Greaves |first=Mel |date=2014-04-22 |title=Was skin cancer a selective force for black pigmentation in early hominin evolution? |journal=Proceedings of the Royal Society B: Biological Sciences |volume=281 |issue=1781 |page=20132955 |doi=10.1098/rspb.2013.2955 |issn=0962-8452|doi-access=free |pmid=24573849 |pmc=3953838 }}</ref> There are also differences in the quantity and relative amounts of [[eumelanin]] and [[pheomelanin]].<ref name="Greaves 2014 p. 20132955" /> Pigmentation including tanning is under hormonal control, including the [[Melanocyte-stimulating hormone|MSH]] and ACTH peptides that are produced from the precursor proopiomelanocortin.

[[Vitiligo]] is a skin disease where people lack melanin in certain areas in the skin.

People with oculocutaneous [[Albinism in humans|albinism]] typically have a very low level of melanin production. Albinism is often but not always related to the ''TYR'' gene coding the [[tyrosinase]] enzyme.  Tyrosinase is required for melanocytes to produce melanin from the [[amino acid]] [[tyrosine]].<ref>{{cite web |url=http://ghr.nlm.nih.gov/gene/TYR|title=TYR |publisher=National Institutes of Health|access-date=23 June 2013}}</ref> Albinism may be caused by a number of other genes as well, like ''OCA2'',<ref>{{cite web |url=http://ghr.nlm.nih.gov/gene/OCA2|title=OCA2 |publisher=National Institutes of Health|access-date=25 March 2016}}</ref> ''SLC45A2'',<ref>{{cite web |url=http://ghr.nlm.nih.gov/gene/SLC45A2|title=SLC45A2 |publisher=National Institutes of Health|access-date=25 March 2016}}</ref> ''TYRP1'',<ref>{{cite web |url=http://ghr.nlm.nih.gov/gene/TYRP1|title=TYRP1 |publisher=National Institutes of Health|access-date=25 March 2016}}</ref> and ''HPS1''<ref>{{cite web |url=http://ghr.nlm.nih.gov/gene/HPS1|title=HPS1 |publisher=National Institutes of Health|access-date=25 March 2016}}</ref> to name some. In all, already 17 types of oculocutaneous albinism have been recognized.<ref>{{cite journal | vauthors = Montoliu L, Grønskov K, Wei AH, Martínez-García M, Fernández A, Arveiler B, Morice-Picard F, Riazuddin S, Suzuki T, Ahmed ZM, Rosenberg T, Li W | title = Increasing the complexity: new genes and new types of albinism | journal = Pigment Cell & Melanoma Research | volume = 27 | issue = 1 | pages = 11–8 | date = January 2014 | pmid = 24066960 | doi = 10.1111/pcmr.12167 | s2cid = 7305884 | doi-access = free }}</ref> Each gene is related to different protein having a role in pigment production.

People with [[Chédiak–Higashi syndrome]] have a buildup of melanin granules due to abnormal function of [[microtubules]].