Anandalakshmi Venkatraman

Association of LOXL1 Gene Polymorphisms with Pseudoexfoliation in the Japanese

PURPOSE The single nucleotide polymorphisms (SNPs) rs1048661, rs3825942, and rs2165241 within the LOXL1 gene were recently found to confer risk of pseudoexfoliation glaucoma (XFG) through pseudoexfoliation syndrome (XFS) in Caucasians. The purpose of this study was to test this association in Japanese subjects with XFS/XFG. METHODS Japanese subjects with clinically diagnosed XFS/XFG and normal control subjects were recruited. Genomic DNA was extracted and the three SNPs of the LOXL1 gene were genotyped by bidirectional sequencing. The association of individual SNPs with XFG/XFS was evaluated by using chi(2) and the Fisher exact test. RESULTS Two hundred nine Japanese patients (106 XFG and 103 XFS) and 172 control subjects were studied. Strong associations were observed for all three SNPs of LOXL1 for XFS (odds ratio [OR] = 13.56, P = 3.39 x 10(-28) for allele T of rs1048661; OR = 10.71, P = 1.49 x 10(-7) for allele G of rs3825942; and OR = 4.55, P = 5.33 x 10(-4) for allele C of rs2165241) and XFG (OR = 25.21, P = 1.44 x 10(-34) for allele T of rs1048661; OR = 11.02, P = 1.40 x 10(-7) for allele G of rs3825942; and OR = 11.89, P = 4.76 x 10(-6) for allele C of rs2165241). The risk-associated alleles of rs1048661 and rs2165241 differed between the Japanese and Caucasians, whereas allele G of rs3825942 was associated with disease in both populations. Conditional analysis indicated that rs3825942 was not independent but correlated highly with rs1048661. The at-risk haplotype T-G-C was present at an approximately two times higher rate (94.7% vs. 50.6%, P = 4.22 x 10(-43)) in cases than in control subjects and conferred a 2.9-fold (95% confidence interval [CI], 2.357-3.464) increased likelihood of XFS. CONCLUSIONS Polymorphisms in the LOXL1 gene confer risk to XFS/XFG in the Japanese, but there are different risk-associated alleles and haplotypes in the Japanese.

Depletion of SLC4A11 Causes Cell Death by Apoptosis in an Immortalized Human Corneal Endothelial Cell Line

PURPOSE To investigate the effects of SLC4A11 gene depletion in human corneal endothelial cells. METHODS To achieve stable downregulation of SLC4A11 gene expression in immortalized human corneal endothelial cells (HCECs), short-hairpin RNA (shRNA) targeted against SLC4A11 was used. Cell growth and viability were determined using the real-time cell analyzer and trypan blue staining respectively. Apoptosis was investigated by Annexin V and TUNEL assays. Alterations in apoptotic gene expression following SLC4A11 silencing were determined using the RT(2)Profiler PCR array for human apoptosis while activation of the apoptotic pathway was ascertained by western analysis. RESULTS SLC4A11 silencing in HCECs could be achieved by stable expression of shRNA targeted against SLC4A11. SLC4A11 knockdown suppressed HCEC growth and reduced HCEC viability compared to the control. This reduction in cell growth is associated with increased apoptosis in SLC4A11-silenced cells. CONCLUSIONS Our data suggest that the reduction of cell number with time in SLC4A11-depleted HCECs is due to an increase in cell death by apoptosis. This suggests that SLC4A11 is necessary for cell survival and may explain the pathologic corneal endothelial cell loss in endotheliopathies due to SLC4A11 mutations.

Toll-Like Receptor 3 Polymorphism rs3775291 Is Not Associated with Choroidal Neovascularization or Polypoidal Choroidal Vasculopathy in Chinese Subjects

Background/Aims: Age-related macular degeneration (AMD) is a leading cause of visual impairment. A single-nucleotide polymorphism (SNP; rs3775291) in the Toll-like receptor 3 (TLR3) gene has recently been implicated in the pathogenesis of AMD in Caucasian populations. The aim of this study was to examine this association in Chinese persons with choroidal neovascularization (CNV) secondary to AMD and polypoidal choroidal vasculopathy (PCV). Methods: This was an observational cross-sectional study in Singapore. Study subjects were of Chinese ethnicity and included patients with exudative maculopathy and normal control subjects. The diagnoses of CNV and PCV were made based on fundus examination, fluorescein angiography and indocyanine green angiography findings. Genomic DNA was extracted, and genotypes were determined by bidirectional DNA sequencing. We compared the allele and genotype frequencies between subjects with CNV and PCV with controls using the software PLINK. Results: A total of 246 subjects with exudative maculopathy (consisting of 126 with CNV and 120 with PCV) and 274 normal control subjects were recruited. The distribution of rs3775291 SNP genotypes for CNV and PCV was not significantly different from that for normal controls. Conclusion: This study indicates that the TLR3 rs3775291 gene polymorphism is not associated with CNV and PCV in Singaporean Chinese patients.

Surgical management and genetic analysis of a Chinese family with the S171P mutation in the UBIAD1 gene, the gene for Schnyder corneal dystrophy

Background: To describe the underlying molecular genetic basis, surgical management and phenotypic variation of Schnyder corneal dystrophy (SCD) identified in a four-generation Chinese family. Methods: This is an interventional case series of 13 members from a non-consanguineous Chinese family. All patients underwent complete ophthalmological examination and slit-lamp photography. Subsequent corneal transplantations were performed (n = 3). Blood samples were taken for DNA extraction and subsequent genetic analysis. Results: Genotyping indicated linkage to the locus at chromosome 1p36. Screening of the UBIAD1 gene identified a highly conserved mutation, Ser171Pro. Phenotypic variation in this large pedigree is similar to that seen in Caucasian patients. Surgical management of patients with anterior lamellar keratoplasty and deep anterior lamellar keratoplasty showed good visual outcomes. Conclusions: The S171P mutation is described for the first time in a Chinese family. This is the largest non-Caucasian pedigree described with SCD. Visual rehabilitation may be performed successfully with lamellar surgical procedures as opposed to full-thickness corneal grafts.

pH Induced Conformational Transitions in the Transforming Growth Factor β-Induced Protein (TGFβIp) Associated Corneal Dystrophy Mutants

Most stromal corneal dystrophies are associated with aggregation and deposition of the mutated transforming growth factor-β induced protein (TGFβIp). The 4th_FAS1 domain of TGFβIp harbors ~80% of the mutations that forms amyloidogenic and non-amyloidogenic aggregates. To understand the mechanism of aggregation and the differences between the amyloidogenic and non-amyloidogenic phenotypes, we expressed the 4th_FAS1 domains of TGFβIp carrying the mutations R555W (non-amyloidogenic) and H572R (amyloidogenic) along with the wild-type (WT). R555W was more susceptible to acidic pH compared to H572R and displayed varying chemical stabilities with decreasing pH. Thermal denaturation studies at acidic pH showed that while WT did not undergo any conformational transition, the mutants exhibited a clear pH-dependent irreversible conversion from αβ conformation to β-sheet oligomers. The β-oligomers of both mutants were stable at physiological temperature and pH. Electron microscopy and dynamic light scattering studies showed that β-oligomers of H572R were larger compared to R555W. The β-oligomers of both mutants were cytotoxic to primary human corneal stromal fibroblast (pHCSF) cells. The β-oligomers of both mutants exhibit variations in their morphologies, sizes, thermal and chemical stabilities, aggregation patterns and cytotoxicities.

Proteomic Analysis of Amyloid Corneal Aggregates from TGFBI-H626R Lattice Corneal Dystrophy Patient Implicates Serine-Protease HTRA1 in Mutation-Specific Pathogenesis of TGFBIp

TGFBI-associated corneal dystrophies are inherited disorders caused by TGFBI gene variants that promote deposition of mutant protein (TGFBIp) as insoluble aggregates in the cornea. Depending on the type and position of amino acid substitution, the aggregates may be amyloid fibrillar, amorphous globular or both, but the molecular mechanisms that drive these different patterns of aggregation are not fully understood. In the current study, we report the protein composition of amyloid corneal aggregates from lattice corneal dystrophy patients of Asian origin with H626R and R124C mutation and compared it with healthy corneal tissues via LC-MS/MS. We identified several amyloidogenic, nonfibrillar amyloid associated proteins and TGFBIp as the major components of the deposits. Our data indicates that apolipoprotein A-IV, apolipoprotein E, and serine protease HTRA1 were significantly enriched in patient deposits compared to healthy controls. HTRA1 was also found to be 7-fold enriched in the amyloid deposits of patients compared to the controls. Peptides sequences (G511DNRFSMLVAAIQSAGLTETLNR533 and Y571HIGDEILVSGGIGALVR588) derived from the fourth FAS-1 domain of TGFBIp were enriched in the corneal aggregates in a mutation-specific manner. Biophysical studies of these two enriched sequences revealed high propensity to form amyloid fibrils under physiological conditions. Our data suggests a possible proteolytic processing mechanism of mutant TGFBIp by HTRA1 and peptides generated by mutant protein may form the β-amyloid core of corneal aggregates in dystrophic patients.

Contents Vol. 45, 2011

Anatomy, Pathology and Cell Biology A. Prescott, Dundee Biochemistry, Molecular Biology and Molecular Genetics J. Graw, Neuherberg Clinical and Epidemiological Research M. Kojima, Kahoku Cornea and Ocular Surface C. Marfurt, Gary, Ind. Glaucoma H. Th ieme, Mainz Immunology and Microbiology U. Pleyer, Berlin Lens and Cataract S. Varma, Baltimore, Md. Miscellaneous U. Pleyer, Berlin Neuro-Ophthalmology and Vision Sciences P. Aydin, Ankara Ocular Oncology M. Jager, Leiden Physiology, Pharmacology and Toxicology A. Wegener, Bonn Retina and Retinal Cell Biology P. Pereira, Coimbra Editorial Board