International Mammalian Genome Society

The 15th International Mouse Genome Conference (2001)


IDENTIFICATION OF THE MOUSE UNDERWHITE (uw) GENE AND ITS HUMAN ORTHOLOGUE: OCULOCUTANEOUS ALBINISM TYPE 4 (OCA4)

Murray Brilliant
University of Arizona College of Medicine
Department of Pediatrics
1501 N. Campbell Ave
Tucson, AZ 85724 USA

Co-Authors: 1)Newton JM, 2)King RA, 1)Gardner JM, 1)Hagiwara N, 1)Cohen-Barak O, 1)Tran WN, 3)Davisson MT
Institutions: 1)University of Arizona, 2)University of Minnesota, 3)The Jackson Laboratory

Mutations in the mouse underwhite (uw) locus lead to hypopigmentation. The fur of mice homozygous for the most severe allele (uw) is a light beige color with white underfur and the eyes are pink at birth but darken somewhat with age. A series of alleles at this locus has been previously described (Sweet et al., J. Heredity, 89:546-51, 1998; Lehman et al., J. Invest. Dermatol., 115:601-606, 2000), with the uw mutant phenotype and residual melanin composition closely resembling that of p mutant mice. Two alleles, uw and uw-dense, are recessive, with uw homozygotes lighter than uw-dense homozygotes. A third allele, Uw-dominant brown, is semidominant. The dominance heirarchy in the allelic series is Uw-dominant brown, wild-type, uw, followed by uw-dense. We have cloned the mouse uw gene and found a dramatic reduction in expression of the encoded transcript in melanocytes homozygous for the uw allele. Point mutations have been found in the uw-dense and Uw-dominant brown alleles. The human ortholog has also been cloned. Humans with mutations in this gene have a new type of albinism, OCA4 that phenotypically resembles OCA2. Thus, the uw protein is a major determinant of normal pigmentation. Studies are underway to determine the function of the encoded protein in the normal production of melanin.


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