HLA-G gene polymorphisms in patients with age-related macular degeneration

Abstract

Purpose : The study aims to determine if genetic polymorphisms in the human leukocyte antigen G (HLA-G) gene are associated with age-related macular degeneration (AMD). HLA-G is important for immunological tolerance, and it is also known to have angiogenic effects. Polymorphisms in the 5’ upstream regulatory (URR) and 3’ untranslated regions (UTR) of HLA-G have been associated with bad prognosis in a number of diseases, especially with respect to the 14 bp insertion/deletion (ins/del).

Methods : DNA was purified from PBMCs from a cohort of 146 AMD patients (early AMD, geographic atrophy and wet AMD) and 123 matched controls and full gene sequencing was performed using Sanger sequencing. Analysis of DNA sequences was performed with Lasergene 12.2 Seqman Pro, and to determine the most probable haplotypes we used the PHASE v.2.1.1 software. The full HLA-G haplotypes were determined in accordance with the nomenclature of Castelli et al., 2011.

Results : The haplotype and allelic distribution of HLA-G did not display any differences when comparing AMD patients with controls. Analyzing the 5’URR and 3’UTR separately did not reveal any differences either. However, if we focused on the 14 bp ins/del polymorphism in the 3’UTR, data showed an interesting difference between patients and controls. The group of patients with wet AMD had a higher percentage of 14 bp ins/del heterozygotes compared to controls and other patient groups.

Conclusions : We have previously shown that HLA-G is expressed in retinal pigment epithelial (RPE) cells in vitro and that HLA-G gene expression is upregulated in the macula of AMD patients. In the current study, we show that there is a higher percentage of patients, who are heterozygous for the 14 bp ins/del polymorphism in the wet AMD group. This is surprising as this genotype is associated with higher levels of HLA-G in plasma. Thus we expected a higher degree of downregulation and protection from immune responses. However, HLA-G can also activate a pro-angiogenic response through engagement of the KIR2DL4 receptor on natural killer (NK) cells. As NK cells have been described in the subretinal lesions in AMD patients, HLA-G expression might be an important factor in development of wet AMD.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

HLA-G 14 bp ins/del genotype combination in AMD patients and controls A) all patients analyzed together B) groups of patients analyzed separately. Samples were included when sequencing data was available (no extrapolated data)