Genetic Analysis of Albinism

• Grant number: 24/05568-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2024
• End date: April 30, 2025
• Field of knowledge: Humanities - Psychology - Physiological Psychology
• Principal Investigator: Dora Selma Fix Ventura
• Grantee: Lais Thomaz Bastos
• Host Institution: Instituto de Psicologia (IP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 22/00191-0 - Mechanisms, genetics and performance of the visual system: clinical research in humans and animal experiments, AP.TEM

Abstract

The clinical term albinism refers to the set of genetically heterogeneous diseases associated with the decrease or absence of melanin production (RIBEIRO, 2019; BAKKER et al., 2022). Hypopigmentation occurs in the eyes and/or skin and hair, together with the abnormal development of the visual system (SANO, 2017; SIMEONOV et al., 2013). The different types of albinism are categorized genotypically, with 22 known genes involved in this clinical picture. The severity of genetic changes in these genes in the melanin production process affects the intensity of the clinical manifestation (BAKKER et al., 2022; SANO, 2017). The global distribution of albinism subtypes varies depending on the origin and ethnicity of the patients and estimates indicate that 1 in every 17,000 individuals has some type of albinism (GRONSKOV et al., 2007; SIMEONOV et al., 2013). Albinism can be classified into Ocular Albinism (OA) and Oculocutaneous Albinism (OCA). Ocular albinism is a rarer type of albinism, characterized by hypopigmentation of the retina and iris, generally presenting normal pigmentation in the rest of the body (RIBEIRO, 2019). This type of albinism is caused by mutations in the GPR143 gene (also known as OA1), which encodes a receptor involved in the biogenesis, organization and transport of melanosomes, and presents a pattern of recessive inheritance linked to the X chromosome (UniProt; BAKKER et al., 2022). Oculocutaneous albinism is a group of autosomal recessive diseases linked to hypopigmentation of the skin, hair and eyes (GRONSKOV et al., 2007). Among the eight known subtypes (OCA 1-8), four are well characterized (OCA 1-4) (BAKKER et al., 2022). Some of the genes involved are related to encoding enzymes necessary in melanogenesis, while others participate in melanosome homeostasis (BAKKER et al., 2022). OCA1 and OCA2 are the most common types of albinism, with the former responsible for 50% of albinism cases globally (RIBEIRO, 2019). The reduction or absence of melanin in the retinal pigmented epithelium causes abnormal development of the retina, with foveal hypoplasia being one of the most common features in albino people (JEFFERY, 1997). The ophthalmological phenotype in albinism is multifactorial and can generate visual impairments and discomfort (SANO, 2017). However, in some patients, fovea formation and normal visual acuity are observed, despite the albino phenotype (SANO, 2017).