Divya Venkataraman

Mutations in sodium-borate cotransporter SLC4A11 cause recessive congenital hereditary endothelial dystrophy (CHED2)

Congenital hereditary endothelial dystrophy (CHED) is a heritable, bilateral corneal dystrophy characterized by corneal opacification and nystagmus. We describe seven different mutations in the SLC4A11 gene in ten families with autosomal recessive CHED. Mutations in SLC4A11, which encodes a membrane-bound sodium-borate cotransporter, cause loss of function of the protein either by blocking its membrane targeting or nonsense-mediated decay.

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.

Lack of association between the rs2664538 polymorphism in the MMP-9 gene and primary angle closure glaucoma in Singaporean subjects.

PurposeA recent study identified the single nucleotide polymorphism (SNP) rs2664538 within the MMP-9 gene with risk for acute primary angle closure glaucoma (PACG). The aim of this study was to confirm this association in Singaporean Chinese subjects with both acute and chronic PACG. MethodsThis was an observational cross-sectional study. Genomic DNA was extracted from leukocytes of peripheral blood and genotypes were determined by polymerase chain reaction and direct sequencing. The association of the SNP with PACG was evaluated using χ2 tests. ResultsA total of 217 subjects with PACG (consisting of 85 acute and 132 chronic PACG), and 83 normal control Chinese subjects were studied. There was no significant difference in the rs2664538 SNP allele frequencies for acute or chronic PACG subjects compared with controls. ConclusionsThis study did not find an association between the rs2664538 polymorphism within the MMP-9 gene and PACG in this sample of Chinese subjects.

A novel mutation in transforming growth factor-beta induced protein (TGFβIp) reveals secondary structure perturbation in lattice corneal dystrophy

Background To describe mutations in the transforming growth factor-beta induced (TGFBI) gene in Asian patients with Bowmans membrane as well as stromal corneal dystrophies, and to elucidate their structural implications, using model peptides. Methods Twenty-two unrelated Asian families were examined clinically including visual acuity testing and ocular examination with slit lamp biomicroscopy. Genomic DNA was extracted and the 17 exons of the TGFBI gene were amplified by PCR and sequenced bi-directionally. Biophysical techniques were used to characterise the wild type and mutant model peptides. Results Molecular genetic analysis identified a variety of mutations in our patient series including a novel heterozygous C to A transversion mutation in exon 14 (c.1859C→A), resulting in a substitution of a highly conserved alanine residue by aspartic acid (p.A620D). Clinical presentation in the patient with the p.A620D included subepithelial scarring in addition to the linear branching opacities usually seen with lattice dystrophy. Using model peptides, we showed that A620D mutant peptide alters the secondary structure and conformational stability, and increased amyloid formation. Conclusion A novel mutation (A620D) in transforming growth factor-beta induced protein (TGFβIp) is described, expanding the repertoire of mutations in this protein. Using model peptides, we demonstrated that A→D substitution leads to perturbation of the secondary structure that may be responsible for the amyloid formation in lattice corneal dystrophy.

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.

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