Haplotype-Based Analysis of OCA2 Variants in Oculocutaneous Albinism

Area of Science:

• Genetics
• Ophthalmology
• Dermatology

Background:

• OCA2 protein regulates melanosomal pH and melanin production.
• OCA2 is a major cause of oculocutaneous albinism (OCA) worldwide.
• GWAS have linked OCA2 variants to pigmentation, skin cancer, and retinal traits.

Purpose of the Study:

• To identify and characterize rare OCA2 variants in OCA probands.
• To investigate the role of common GWAS alleles and rare variants in OCA2 haplotypes.
• To assess the impact of haplotype combinations on OCA2 gene function.

Main Methods:

• Analysis of 106 OCA2 probands with biallelic OCA2 variants.
• Identification of 74 distinct rare OCA2 variants (structural, indel/frameshift, splice site, missense).
• Phase-validated haplotype analysis combining common GWAS alleles and rare variants.

Main Results:

• Identified 41 distinct multi-allele OCA2 haplotypes in 95 probands.
• 27 haplotypes contained rs1800404-A and/or rs12913832-G alleles, affecting splicing/expression.
• Common GWAS alleles with known function were found on haplotypes with variants of unknown significance.

Conclusions:

• Haplotype-based analysis is essential for understanding OCA2 locus variation.
• Interactions between common and rare OCA2 variants influence gene function.
• This highlights the need to consider haplotype context beyond individual variant assessment for OCA diagnosis.