TYR Gene in Llamas: Polymorphisms and Expression Study in Different Color Phenotypes

ANELLO, MELINA; FERNÁNDEZ, ESTEFANÍA; DAVERIO, MARÍA SILVANA; ARBELETCHE VIDAL-RIOJA, LIDIA; DI ROCCO, FLORENCIA

Frontiers in Genetics

Frontiers in Genetics | www.frontiersin.org

Lugar: Lausana; Año: 2019 vol. 10 p. 1 - 9

Tyrosinase, encoded by TYR gene, is an enzyme that plays a major role in mammalianpigmentation. It catalyzes the oxidation of L-dihydroxy-phenylalanine (DOPA) to DOPAquinone, a precursor of both types of melanin: eumelanin and pheomelanin. TYR iscommonly known as the albino locus since mutations in this gene result in albinism inseveral species. However, many other TYR mutations have been found to cause dilutedphenotypes, like the Himalayan or chinchilla phenotypes in mice. The llama (Lamaglama) presents a wide variety of coat colors ranging from non-diluted phenotypes(eumelanic and pheomelanic), through different degrees of dilution, to white. Toinvestigate the possible contribution of TYR gene to coat color variation in llamas, wesequenced TYR exons and their flanking regions and genotyped animals with diluted,non-diluted, and white coat, including three blue-eyed white individuals. Moreover,we analyzed mRNA expression levels in skin biopsies by qPCR. TYR coding regionpresented nine SNPs, of which three were non-synonymous, c.428A > G, c.859G > T,and c.1490G > T. We also identified seven polymorphisms in non-coding regions,including two microsatellites, an homopolymeric repeat, and five SNPs: one in thepromoter region (c.1-26C > T), two in the 30-UTR, and two flanking the exons. Althoughno complete association was found between coat color and SNPs, c.1-26C > T waspartially associated to diluted phenotypes. Additionally, the frequency of the G allelefrom c.428A > G was significantly higher in white compared to non-diluted. Resultsfrom qPCR showed that expression levels of TYR in white llamas were significantlylower (p < 0.05) than those in diluted and non-diluted phenotypes. Screening forvariation in regulatory regions of TYR did not reveal polymorphisms that explain suchdifferences. However, data from this study showed that TYR expression levels play arole in llama pigmentation.