ABSTRACT
PLEKHA7, a gene recently associated with primary angle closure glaucoma (PACG), encodes an apical junctional protein expressed in components of the blood aqueous barrier (BAB). We found that PLEKHA7 is down-regulated in lens epithelial cells and in iris tissue of PACG patients. PLEKHA7 expression also correlated with the C risk allele of the sentinel SNP rs11024102 with the risk allele carrier groups having significantly reduced PLEKHA7 levels compared to non-risk allele carriers. Silencing of PLEKHA7 in human immortalized non-pigmented ciliary epithelium (h-iNPCE) and primary trabecular meshwork cells, which are intimately linked to BAB and aqueous humor outflow respectively, affected actin cytoskeleton organization. PLEKHA7 specifically interacts with GTP-bound Rac1 and Cdc42, but not RhoA, and the activation status of the two small GTPases is linked to PLEKHA7 expression levels. PLEKHA7 stimulates Rac1 and Cdc42 GTP hydrolysis, without affecting nucleotide exchange, identifying PLEKHA7 as a novel Rac1/Cdc42 GAP. Consistent with the regulatory role of Rac1 and Cdc42 in maintaining the tight junction permeability, silencing of PLEKHA7 compromises the paracellular barrier between h-iNPCE cells. Thus, downregulation of PLEKHA7 in PACG may affect BAB integrity and aqueous humor outflow via its Rac1/Cdc42 GAP activity, thereby contributing to disease etiology.
Subject(s)
Carrier Proteins/genetics , Glaucoma, Angle-Closure/genetics , cdc42 GTP-Binding Protein/genetics , rac1 GTP-Binding Protein/genetics , Blood-Aqueous Barrier/metabolism , Carrier Proteins/metabolism , Cell Movement/genetics , Epithelial Cells/metabolism , Genetic Predisposition to Disease , Glaucoma, Angle-Closure/metabolism , Glaucoma, Angle-Closure/pathology , Humans , Intercellular Junctions/metabolism , Iris/metabolism , Iris/pathology , Polymorphism, Single Nucleotide , Tight Junctions/metabolism , cdc42 GTP-Binding Protein/metabolism , rac1 GTP-Binding Protein/metabolismABSTRACT
Nuclear cataract is the most common type of age-related cataract and a leading cause of blindness worldwide. Age-related nuclear cataract is heritable (h2 = 0.48), but little is known about specific genetic factors underlying this condition. Here we report findings from the largest to date multi-ethnic meta-analysis of genome-wide association studies (discovery cohort N = 14,151 and replication N = 5299) of the International Cataract Genetics Consortium. We confirmed the known genetic association of CRYAA (rs7278468, P = 2.8 × 10-16) with nuclear cataract and identified five new loci associated with this disease: SOX2-OT (rs9842371, P = 1.7 × 10-19), TMPRSS5 (rs4936279, P = 2.5 × 10-10), LINC01412 (rs16823886, P = 1.3 × 10-9), GLTSCR1 (rs1005911, P = 9.8 × 10-9), and COMMD1 (rs62149908, P = 1.2 × 10-8). The results suggest a strong link of age-related nuclear cataract with congenital cataract and eye development genes, and the importance of common genetic variants in maintaining crystalline lens integrity in the aging eye.