Novel SLC45A2 Mutations in OCA4 Italian Albinos Patients

Abstract

Purpose: : To define SLC45A2 genetic variation frequencies in Italian population affected by oculocutaneous albinism and negative for TYR, P-protein, TYRP1 and GPR143 gene defects associated to the clinical Albinism phenotype.

Methods: : After clinical examination and instrumental evaluation by our Ophthalmologic Centre, all affected patients received a genetic counseling and signed an informed consent to the genetic study. Blood sample was collected from each individual and , when possible, also from parents. After DNA extraction, different PCR amplifications and automatic sequences of TYR, P-protein, TYRP1 genes were performed. 21 patients were then analyzed for SLC45A2 gene. SeqScape software analysis was then applied to individuate DNA variations.

Results: : All analyzed patients present an heterogeneous phenotype, but the major clinical albinism signs were present. Four patients out of 21 displayed mutations in SLC45A2 gene. We identified 4 DNA variants; three of them were missense mutations: c. 606 G>C p. W202C, c. 793 A>T p.M265L and c. 1532 C>A p.A511E, and the other one was a splice-site mutation: IVS5+1 G>A .Two of them have never been described: c. 793 A>T p.M265L and IVS5+1 G>A . Two out of the four patients have two mutated alleles: one presents the p.A511E mutation in homozygous state, the other harbors the p. W202C and the IVS5+1 G>A mutations in compound heterozygosity. The two other albinos present only one mutation in heterozygosis: p.M265L and p. W202C respectively.

Conclusions: : In our cohort of albinos patients only 3% present molecular defects in SLC45A2. A previous new digenic form (involving P-protein and TYRP1) was identified from our group for the first time, the additional evidence of two patients with only one OCA4 mutated allele support our hypothesis of digenic hereditary may be with new unknown genes associated to melanin pathway.

Keywords: gene screening • melanocytes • mutations