TYRP1 gene

• Overview
• Albinism
• Additional information
• References

Overview

Gene (OMIM no.)	TYRP1 (#115501)
Function of gene/protein	Protein: tyrosinase-related protein 1 Involved in eumelanin synthesis in melanosomes along with tyrosinase Catalyses the oxidation of catalysing the oxidation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) monomers into eumelanin (Gronskov 2007) Also involved in maintaining stability of tyrosinase and melanosome ultrastructure
Clinical phenotype (with OMIM phenotype no.)	Albinism, oculocutaneous, type III; OCA1A (#203290) [Skin/hair/eye pigmentation, variation in, 11 (Melanesian blond hair)] (#612271)
Inheritance	Autosomal recessive
Ocular features	The ocular phenotype and visual function are highly variable among individuals but tend to be less severe overall than other OCA types. They may have some/all of the following features: Decreased visual acuity Nystagmus Strabismus Photophobia Iris transillumination Foveal hypoplasia Fundal hypopigmentation Chiasmal misrouting detected on visual evoked potential (VEP) testing due to abnormally increased number of axons crossing the optic chiasm to innervate the contralateral cortex
Systemic features	“Rufous” OCA Predominantly affects Africans Reddish brown/lightly pigmented skin in non-Africans Red/reddish yellow (ginger) hair with orange highlights
Key investigations	Orthoptic assessment and refraction OCT to detect foveal hypoplasia Electrophysiology (pattern/flash VEP) to detect chiasmal misrouting Eye movement recordings Systemic assessment with dermatologists and other relevant specialist if syndromic OCA (e.g. Hermansky-Pudlak or Chediak-Higashi syndrome) is suspected
Molecular diagnosis	Next generation sequencing Targeted gene panels (albinism) Whole exome sequencing Whole genome sequencing
Management	Management of albinism
Therapies under research	Current research in albinism
Further information	Genetics Home Reference

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Additional information

OCA3 affects predominantly Africans, with a prevalence of up to 1:8500 being reported^[6] but cases have been reported in other ethnicities as well.^[7–10] There are two common variants among southern Africans, p.S166X and c.368delA, both of which are nonsense mutations and account for 90% of rufous OCA among that population.^[11]

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References

1. Wiriyasermkul P, Moriyama S, Nagamori S. Membrane transport proteins in melanosomes: Regulation of ions for pigmentation. Biochim Biophys Acta Biomembr. 2020;1862(12):183318.
2. Grønskov K, Ek J, Brondum-Nielsen K. Oculocutaneous albinism. Orphanet J Rare Dis. 2007;2(43).
3. Sarangarajan R, Boissy RE. Tyrp1 and oculocutaneous albinism type 3. Pigment Cell Res. 2001;14(6):437-444.
4. Boissy RE, Zhao H, Oetting WS, et al. Mutation in and lack of expression of tyrosinase-related protein-1 (TRP-1) in melanocytes from an individual with brown oculocutaneous albinism: a new subtype of albinism classified as “OCA3”. Am J Hum Genet. 1996;58(6):1145-1156.
5. Manga P, Kerr R, Ramsay M, Kromberg JG. Biology and genetics of oculocutaneous albinism and vitiligo – common pigmentation disorders in southern Africa. S Afr Med J. 2013;103(12 Suppl 1):984-988. Published 2013 Jul 29.
6. Kromberg JG, Castle DJ, Zwane EM, et al. Red or rufous albinism in southern Africa. Ophthalmic Paediatr Genet. 1990;11(3):229-235.
7. Forshew T, Khaliq S, Tee L, et al. Identification of novel TYR and TYRP1 mutations in oculocutaneous albinism. Clin Genet. 2005;68(2):182-184.
8. Kausar T, Jaworek TJ, Tariq N, et al. Genetic studies of TYRP1 and SLC45A2 in Pakistani patients with nonsyndromic oculocutaneous albinism. J Invest Dermatol. 2013;133(4):1099-1102.
9. Rooryck C, Roudaut C, Robine E, Müsebeck J, Arveiler B. Oculocutaneous albinism with TYRP1 gene mutations in a Caucasian patient. Pigment Cell Res. 2006;19(3):239-242.
10. Chiang PW, Spector E, Scheuerle A. A case of Asian Indian OCA3 patient. Am J Med Genet A. 2009;149A(7):1578-1580.
11. Manga P, Kromberg JG, Box NF, Sturm RA, Jenkins T, Ramsay M. Rufous oculocutaneous albinism in southern African Blacks is caused by mutations in the TYRP1 gene. Am J Hum Genet. 1997;61(5):1095-1101.

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