Characterization of Novel SLC4A11 Mutations Identified in Recessive Congenital Hereditary Endothelial Dystrophy (CHED2)

MORGAN PE, SAINCHER M, VITHANA E, RAMPRASAD, V, KUMARAMANICKEVEL G, AUNG T AND CASEY JR

Fort Lauderdale

Congreso; ARVO; 2007

Purpose- The endothelial (posterior) corneal dystrophies, which result from primary endothelial dysfunction, include Fuchs endothelial dystrophy (FECD), posterior polymorphism dystrophy (PPCD) and congenital hereditary endothelial dystrophy (CHED). As they share common features of disease it is possible that a proportion of them could be clinical manifestations of different mutations of the same gene. Accordingly Mutations in COL8A2 gene which encodes the alpha 2 (VIII) collagen chain have been identified in both familial and sporadic FECD as well as in a family with PPCD. The aim of our work was to determine whether mutations in the SLC4A11 gene, recently implicated in recessive CHED may also play a pathogenetic role in the development of the more common Fuchs corneal endothelial dystrophy. Method-Exons 1-19 of SLC4A11 gene was PCR amplified in 90 FECD cases (64 Chinese and 26 Indian) and then subject to bi-directional sequencing using BigDye Terminator v3.1 chemistries and analysed on an ABI PRISM 3100 Genetic Analyser. Eighty Chinese and 30 Indian samples were used as normal age matched controls. Wild type and mutant cDNA constructs were transfected in to HEK293 cells and protein extracts used for western analysis and cell surface processing assays. Confocal immunolocalization were also performed using established protocols. Results-Four heterozygous mutations absent in ethnically matched controls were identified in this screen of 90 FECD patients. These were three missense mutations (E399K, G709E and T754M) and one deletion mutation (99-100delTC). In addition, several silent mutations and conservative amino acid substitutions present in both FECD patients and controls were also identified. Missense mutations involved amino acid residues showing high interspecies conservation indicating that mutations at these sites would be deleterious. Accordingly, western analysis, cell surface processing assays and confocal immunolocalizations showed that missense mutants failed to be processed to the cell surface. This suggests that functional loss of one copy of the SLC4A11 can predispose individuals to FECD.  Conclusion- Preliminary data indicate that SLC4A11 may play a role in the pathogenesis of FECD through haploinsufficiency.