Tyrosinase gene mutations associated with type IB (yellow) oculocutaneous albinism

We have identified three different tyrosinase gene mutant alleles in four unrelated patients with type IB ("yellow") oculocutaneous albinism (OCA) and thus have demonstrated that type IB OCA is allelic to type IA (tyrosinase negative) OCA. In an inbred Amish kindred, type IB OCA results fr...

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Bibliographic Details
Published in:American journal of human genetics 1991-06, Vol.48 (6), p.1159-1167
Main Authors: GIEBEL, L. B, TRIPATHI, R. K, STRUNK, K. M, HANIFIN, J. M, JACKSON, C. E, KIING, R. A, SPRITZ, R. A
Format: Article
Language:English
Subjects:
albinism
Albinism, Oculocutaneous - genetics
Alleles
Amino Acid Sequence
Aminoacid disorders
Base Sequence
Biological and medical sciences
Codon
Errors of metabolism
genes
HeLa Cells
Heterozygote
Homozygote
Humans
Medical sciences
Metabolic diseases
Molecular Sequence Data
Monophenol Monooxygenase - genetics
Mutation
Nucleic Acid Hybridization
Oligonucleotide Probes
Pedigree
Polymerase Chain Reaction
Transfection
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Summary:We have identified three different tyrosinase gene mutant alleles in four unrelated patients with type IB ("yellow") oculocutaneous albinism (OCA) and thus have demonstrated that type IB OCA is allelic to type IA (tyrosinase negative) OCA. In an inbred Amish kindred, type IB OCA results from homozygosity for a Pro---Leu substitution at codon 406. In the second family, type IB OCA results from compound heterozygosity for a type IA OCA allele (codon 81 Pro---Leu) and a novel type IB allele (codon 275 Val---Phe). In the third patient, type IB OCA results from compound heterozygosity for the same type IB allele (codon 275 Val---Phe) and a novel type IB OCA allele. In a fourth patient, type IB OCA results from compound heterozygosity for the codon 81 type IA OCA allele and a type IB allele that contains no identifiable abnormalities; dysfunction of this type IB allele apparently results from a mutation either well within one of the large introns or at some distance from the tyrosinase gene. In vitro expression of the Amish type IB allele in nonpigmented HeLa cells demonstrates that the Pro---Leu substitution at codon 406 greatly reduces but does not abolish tyrosinase enzymatic activity, a finding consistent with the clinical phenotype.
ISSN:0002-9297
1537-6605