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Complete Oculocutaneous Albinism Type I (TYR gene)

Complete Oculocutaneous Albinism Type I (TYR gene)

Oculocutaneous albinism type I results from mutations in the TYR gene, which causes a lack of melanin in the hair, skin and eyes.

Definition

Oculocutaneous albinism type I is characterized by the congenital absence of pigment in most of the body, resulting in an all-white coat and distinctive light blue or pink eyes. This condition is caused by mutations in the TYR gene, which encodes the enzyme tyrosinase, crucial for melanin production. Deficiency of this enzyme prevents melanin synthesis, resulting in lack of coloration.

Genetic basis

The C locus in the TYR gene determines coat coloration. At this locus there is the following allelic series: C > c^b = c^s > c, c^2. The C allele corresponds to the wild-type allele that produces melanin. In this case, we analyzed the c allele that causes complete albinism due to the c.939del deletion in the TYR gene. This trait is inherited in an autosomal recessive manner, which means that it requires the presence of two copies of the genetic variant for the expression of the phenotype. Cats that have only one copy of this variant will not show the trait, but can transmit the allele to their offspring with a 50% probability.

Other relevant information

Other alleles of the same C locus are associated with other characteristic coats: the C allele allows normal melanin production, while the c^b (Burmese cat) and c^s (Siamese cat) alleles reduce melanin production, creating specific color patterns.

Bibliography

Imes DL, Geary LA, Grahn RA, et al. Albinism in the domestic cat (Felis catus) is associated with a tyrosinase (TYR) mutation. Anim Genet. 2006