Type I oculocutaneous albinism (OCA1) associated with a large deletion of the tyrosinase (TYR) gene

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · American Journal of Human Genetics

OSTI ID:134330

Spritz, R A; Wick, P A; Holmes, S A; Schnur, R E ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)

OCA1 is an autosomal recessive disorder in which the biosynthesis of melanin is reduced or absent in skin, hair, and eyes, due to deficient enzymatic activity of tyrosinase. TYR consists of 5 exons spanning over 65 kb at 11q14-q21. Analyses of TYR in >400 unrelated patients with OCA1 have identified more than 50 different point mutations; however, no large deletions have been detected. Here we report a large deletion of TYR in a Caucasian boy with OCA1B. Simultaneous SSCP/heteroduplex screening and DNA sequence analysis indicated that the patient was apparently homozygous for a previously described TYR mutation, adjacent to the 3` splice site of IVS2 (-7, t{r_arrow}a). To distinguish between possible gene deletion vs. maternal uniparental isodisomy, we characterized several chromosome 11 polymorphisms. Maternal uniparental isodisomy was excluded by the patient`s heterozygosity for alleles at D11S35 (11q21-122) and HBG2 (11p15.5). In addition, the patient failed to inherit paternal alleles at an MboI RFLP in exon 1 of TYR and at a TaqI RFLP in the promoter region of the gene. To detect a possible submicroscopic deletion, we performed quantitative Southern blot hybridization using a full length TYR cDNA. Compared with controls, both the patient and his father appeared deleted for two or three TYR-derived PstI fragments; the two TYRL-derived fragments appeared normal. These data indicate that the patient and his father have a partial TYR deletion, including at least exons 1, 2, and IVS2. Based on the organization of the gene, this deletion is at least 50 kb in size. The patient is thus hemizygous for the maternally-inherited mutation in IVS2, accounting for his OCA1B phenotype.

• OSTI ID: 134330
• Report Number(s): CONF-941009--
• Journal Information: American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: Suppl.3 Vol. 55; ISSN AJHGAG; ISSN 0002-9297
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
BIOLOGICAL MARKERS
BIOSYNTHESIS
DETECTION
DNA HYBRIDIZATION
DNA SEQUENCING
EXONS
FLUORESCENCE
GENE MUTATIONS
GENE REPRESSORS
GENES
GENETIC MAPPING
HEREDITARY DISEASES
HUMAN CHROMOSOMES
KARYOTYPE
MELANIN
PATIENTS
PHENOTYPE
PROBES
RECESSIVE MUTATIONS
RFLPS
SCREENING
SIZE
SKIN DISEASES
SPLICING
TYROSINASE