Evaluation of the effect of intravitreal ranibizumab injections in patients with neovascular age related macular degeneration on retinal nerve fiber layer thickness using optical coherence tomography

Purpose

To evaluate the effect of repeated intravitreal ranibizumab injections for neovascular age related macular degeneration (nAMD) on the retinal nerve fiber layer (RNFL) thickness using optical coherence tomography.

Design

A prospective observational cohort study of patients with nAMD.

Methods

Thirty eyes of 30 patients with nAMD were selected. All patients received three ranibizumab injections and underwent scans using the fast RNFL thickness protocol (Stratus optical coherence tomography) before starting the first injection and 1 month after the third injection. The RNFL thickness measurements prior to the injections and after the third injection were used for the analysis. We also evaluated the effect of the lens status as well as the type of choroidal neovascular membrane on RNFL thickness measurements pre- and post-injection. Pre- and post-injection average and individual quadrant RNFL thickness were measured and statistically analyzed.

Results

The mean (± standard deviation) pre-injection RNFL thickness was 90.8±18. The mean (± standard deviation) post-injection RNFL thickness was 91.03±15. The pre- and post-injection values of the mean RNFL thickness were not statistically significant. Likewise, the pre- and post-injection values for RNFL thickness in the different quadrants were not statistically significant. There was no statistical significance for the lens status or the type of choroidal neovascular membrane on the RNFL thickness.

Conclusion

Repeated ranibizumab injections in nAMD appear to have no harmful effect on the RNFL thickness in the short term, in spite of the proven neurotrophic effect of vascular endothelial growth factor. Nevertheless, the safety profile of ranibizumab injections in nAMD needs to be further evaluated in a large multicenter trial with special emphasis on the long-term effects on the retina and optic nerve.

Identification of novel mutations in the ortholog of Drosophila eyes shut gene (EYS) causing autosomal recessive retinitis pigmentosa

PURPOSE

Recently, a novel gene was cloned for autosomal recessive retinitis pigmentosa (arRP), EYS, on 6q12. This study was conducted to determine the spectrum and frequency of EYS mutations in 195 unrelated patients with autosomal recessive and autosomal dominant RP (adRP).

METHODS

All cases had a complete ophthalmic examination, and the clinical diagnosis of RP was based on visual acuity, fundus photography, and electroretinography findings. The DNA extracted from all participants was subjected to molecular genetic analysis entailing amplification of the coding regions and exon-intron boundaries of EYS by polymerase chain reaction, followed by direct sequencing. Bioinformatics analysis was undertaken to study the effect of the identified mutations on protein structure and function.

RESULTS

Eleven novel missense, nonsense, and splice site mutations were identified within EYS in 10 unrelated arRP patients, with probable allele frequency of 11%. However, no mutations were observed in the adRP panel. In addition, 53 single-nucleotide polymorphisms (SNPs) were found, of which 12 were previously unreported. Bioinformatics analyses revealed that all mutations were highly conserved across other species and/or involved important domains on protein structure. Intrafamilial phenotypic variability was also observed in a family with double heterozygous mutations.

CONCLUSIONS

This is the first report of molecular genetic analysis of EYS in a cohort of unrelated British and Chinese patients with RP. The results further the initial hypothesis that EYS is a major causative gene for recessive RP and emphasize the role of different types of mutations in disrupting the function of EYS.

Molecular genetic study of Egyptian patients with macular corneal dystrophy

AIM

To identify the underlying genetic defect in Egyptian patients with macular corneal dystrophy (MCD).

METHODS

A clinical and molecular genetic study was performed on 11 patients from six families with MCD. Clinical diagnosis was confirmed by slit-lamp biomicroscopy and histopathological examination of corneal buttons following keratoplasty. The coding region of the carbohydrate sulfotransferase (CHST6) gene was amplified by polymerase chain reaction (PCR) in all affected subjects. This was followed by direct sequencing and restriction digest analyses. Enzyme-linked immunosorbent assay of antigenic keratan sulfate (KS) in patients' serum was also performed.

RESULTS

Six homozygous mutations, of which three are novel, were identified within the coding region of CHST6 in six unrelated MCD families. The barely detectable level of antigenic KS in the serum of the affected individuals indicated that they all have MCD type I, including the subtype IA.

CONCLUSIONS

This is the first report of a molecular genetic analysis of MCD in the Egyptian population. These data indicate the extensive allelic heterogeneity within CHST6 and further support its essential role in maintaining corneal transparency.

Molecular Genetic Analysis of Two Functional Candidate Genes in the Autosomal Recessive Retinitis Pigmentosa, RP25, Locus

PURPOSE

To identify the disease gene in five Spanish families with autosomal recessive retinitis pigmentosa (arRP) linked to the RP25 locus. Two candidate genes, EEF1A1 and IMPG1, were selected from the region between D6S280 and D6S1644 markers where the families are linked. The genes were selected as good candidates on the basis of their function, tissue expression pattern, and/or genetic data.

METHODS

A molecular genetic study was performed on DNA extracted from one parent and one affected member of each studied family. The coding exons, splice sites, and the 5' UTR of the genes were amplified by polymerase chain reaction (PCR). For mutation detection, direct sequence analysis was performed using the ABI 3100 automated sequencer. Segregation of an IMPG1 single nucleotide polymorphism (SNP) in all the families studied was analyzed by restriction enzyme digest of the amplified gene fragments.

RESULTS

In total, 15 SNPs were identified of which 7 were novel. Of the identified SNPs, one was insertion, two were deletions, five were intronic, six were missense, and one was located in the 5' UTR. These changes, however, were also identified in unaffected members of the families and/or 50 control Caucasians. The examined known IMPG1 SNP was not segregating with the disease phenotype but was correlating with the genetic data in all families studied.

CONCLUSIONS

Our results indicate that neither EEF1A1 nor IMPG1 could be responsible for RP25 in the studied families due to absence of any pathogenic variants. However, it is important to notice that the methodology used in this study cannot detect larger deletions that lie outside the screened regions or primer site mutations that exist in the heterozygous state. A role of both genes in other inherited forms of RP and/or retinal degenerations needs to be elucidated.

Molecular analysis of the VSX1 gene in familial keratoconus

PURPOSE

To evaluate the role of the visual system homeobox gene 1 (VSX1) in the pathogenesis of familial keratoconus.

METHODS

Families with two or more individuals with keratoconus were recruited and their members examined. The coding region and intron-exon junctions of the VSX1 gene were sequenced in affected individuals. In cases where there were possible pathogenic changes, segregation within the pedigree was analyzed. Meta analysis of reports on an association of p.D144E change with keratoconus phenotype was performed.

RESULTS

Probands from a panel of 85 apparently unrelated keratoconus families were included. Eleven sequence variants were observed, including the previously reported c.432C>G (p.D144E) change and two novel intronic single nucleotide polymorphisms. However, these three changes did not cosegregate with the disease phenotype.

CONCLUSIONS

We excluded the c.432C>G sequence alteration as the direct cause of the disease. Lack of possibly pathogenic VSX1 sequence variants in the familial panel suggests that involvement of this gene in the pathogenesis of keratoconus is likely to be confined to a small number of pedigrees, at least in the population studied.

Genetic analysis of FAM46A in Spanish families with autosomal recessive retinitis pigmentosa: characterisation of novel VNTRs

Retinitis pigmentosa (RP) is a group of retinal dystrophies characterised primarily by rod photoreceptor cell degeneration. Exhibiting great clinical and genetic heterogeneity, RP be inherited as an autosomal dominant (ad) and recessive (ar), X-linked (xl) and digenic disorder. RP25, a locus for arRP, was mapped to chromosome 6p12.1-q14.1 where several retinal dystrophy loci are located. A gene expressed in the retina, FAM46A, mapped within the RP25 locus, and computational data revealed its involvement in retinal signalling pathways. Therefore, we chose to perform molecular evaluation of this gene as a good candidate in arRP families linked to the RP25 interval. A comprehensive bioinformatic and retinal tissue expression characterisation of FAM46A was performed, together with mutation screening of seven RP25 families. Herein we present 4 novel sequence variants, of which one is a novel deletion within a low complexity region close to the initiation codon of FAM46A. Furthermore, we have characterised for the first time a coding tandem variation in the Caucasian population. This study reports on bioinformatic and moleculardata for the FAM46A gene that may give a wider insight into the putative function of this gene and its pathologic relevance to RP25 and other retinal diseases mapping within the 6q chromosomal interval.

Novel SLC4A11 mutations in patients with recessive congenital hereditary endothelial dystrophy (CHED2). Mutation in brief #958. Online

Autosomal recessive congenital hereditary endothelial dystrophy (CHED2) is a severe and rare corneal disorder that presents at birth or shortly thereafter, characterized by corneal opacification and nystagmus. Recently the gene for CHED2 was identified and seven different mutations in the SLC4A11 gene were reported. Here, we report seven novel mutations and two previously identified mutations in families from India and the United Kingdom with recessive CHED. The novel changes include two nonsense (p.Trp240X; p.Gln800X) three missense (p.Glu143Lys; p.Cys386Arg; p.Arg755Trp) and two splice site mutations (c.2240+1G>A; c.2437-1G>A). Interestingly, the c.2398C>T (p.Gln800X) and c.2437-1G>A identified in two affected siblings represent the first compound heterozygous mutations in the SLC4A11 gene.

Large-scale molecular analysis of a 34 Mb interval on chromosome 6q: major refinement of the RP25 interval

A large scale bioinformatics and molecular analysis of a 34 Mb interval on chromosome 6q12 was undertaken as part of our ongoing study to identify the gene responsible for an autosomal recessive retinitis pigmentosa (arRP) locus, RP25. Extensive bioinformatics analysis indicated in excess of 110 genes within the region and we also noted unfinished sequence on chromosome 6q in the Human Genome Database, between 58 and 61.2 Mb. Forty three genes within the RP25 interval were considered as good candidates for mutation screening. Direct sequence analysis of the selected genes in 7 Spanish families with arRP revealed a total of 244 sequence variants, of which 67 were novel but none were pathogenic. This, together with previous reports, excludes 60 genes within the interval ( approximately 55%) as disease causing for RP. To investigate if copy number variation (CNV) exists within RP25, a comparative genomic hybridization (CGH) analysis was performed on a consanguineous family. A clone from the tiling path array, chr6tp-19C7, spanning approximately 100-Kb was found to be deleted in all affected members of the family, leading to a major refinement of the interval. This will eventually have a significant impact on cloning of the RP25 gene.

Linkage validation of RP25 Using the 10K genechip array and further refinement of the locus by new linked families

Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous group of retinal dystrophies, characterised by rod photoreceptor cell degeneration with autosomal recessive RP (arRP) as the commonest form worldwide. To date, a total of 26 loci have been reported for arRP, each having a prevalence of 1-5%, except for the RP25 locus which was identified as the genetic cause of 14% of arRP cases in Spain. In order to validate the original linkage of RP25, we undertook a total genome scan using the 10K GeneChip mapping array on three of the previously linked families. The data obtained supported the initial findings of linkage. Additionally, linkage analysis in 18 newly ascertained arRP families was performed using microsatellite markers spanning the chromosome 6p12.1-q15 interval. Five out of the 18 families showed suggestive evidence of linkage to RP25, hence supporting the high prevalence of this locus in the Spanish population. Furthermore, the finding of a crossover in one of these families is likely to have refined the disease interval from the original 16 cM to only a 2.67 cM region between D6S257 and D6S1557.

A Clinical and Molecular Genetic Study of Egyptian and Saudi Arabian Patients With Primary Congenital Glaucoma (PCG)

PURPOSE

To undertake mutation screening of cytochrome P4501B1 (CYP1B1, OMIM 601771) and myocilin (MYOC, OMIM 601652) genes in Egyptian and Saudi Arabian patients with primary congenital glaucoma (PCG).

PATIENTS AND METHODS

A clinical and molecular genetic study was performed on 11 Egyptian and Saudi Arabian patients with PCG. Clinical diagnosis was confirmed by slit lamp biomicroscopy, gonioscopy, measurement of intraocular pressure, and corneal diameter. The coding regions of CYP1B1 and MYOC genes were amplified by polymerase chain reaction for all affected subjects. Direct sequence analysis was performed to search for sequence alterations. Haplotype analysis and genotype/phenotype correlation were carried out.

RESULTS

Three CYP1B1 mutations were identified in 5 PCG patients (45.4%) of which 2 were novel (homozygous E173K and heterozygous N498D) and the third (G61E) had previously been reported. In addition 10 single nucleotide polymorphisms were identified in CYP1B1 and MYOC genes of which 2 were novel. However, no pathologic changes in either of the genes were detected in the remaining 6 patients.

CONCLUSIONS

This is the first report of molecular genetic analysis of PCG in the Egyptian population in which 2 novel mutations have been identified. It is possible that these mutations are specific to this population and may lead to alterations in the protein structure encoded by the gene. Patients with no mutations in the screened genes may have mutations in genes yet to be identified.

A novel genetic study of Chinese families with autosomal recessive retinitis pigmentosa

Autosomal recessive retinitis pigmentosa (arRP) is the commonest form of RP worldwide. To date 22 loci have been implicated in the pathogenesis of this disease; however none of these loci independently account for a significant proportion of recessive RP. Linkage studies of arRP in consanguineous families have been mainly based on homozygosity mapping, but this strategy cannot be applied in the case of non-consanguineous families. Therefore, we implemented a systematic approach for identifying the disease locus in three non-consanguineous Chinese families with arRP. Initially, linkage analysis using SNPs/microsatellite markers or mutation screening of known arRP genes excluded all loci/genes except RP25 on chromosome 6. Subsequently a whole genome scan for the three families using the 10K GeneChip Mapping Array was performed, in order to identify the possible disease locus. To the best of our knowledge this is the first report on the utilisation of the 10K GeneChip to study linkage in non-consanguineous Chinese arRP. This analysis indicates that the studied families are probably linked to the RP25 locus, a well defined arRP locus in other populations. The identification of another ethnic group linked to RP25 is highly suggestive that this represents a major locus for arRP.

Exclusion of Four Candidate Genes, KHDRBS2, PTP4A1, KIAA1411 and OGFRL1, as Causative of Autosomal Recessive Retinitis Pigmentosa

To identify the disease gene in 6 Spanish families with autosomal recessive retinitis pigmentosa linked to the RP25 locus, mutation screening of 4 candidate genes, KHDRBS2, PTP4A1, KIAA1411 and OGFRL1, was undertaken based on their expression or functional relevance to the retina. Twenty-six single nucleotide polymorphisms were identified, of which 14 were novel. Even though no pathological mutations were detected, these genes however remain as good candidates for other retinal degenerations mapping to the same chromosomal region.

Novel CHST6 nonsense and missense mutations responsible for macular corneal dystrophy

PURPOSE

To identify the underlying mutations in two unrelated British families with macular corneal dystrophy (MCD) by screening the carbohydrate sulfotransferase (CHST6) gene.

DESIGN

Case reports and results of DNA analysis.

METHODS

Two subjects from two British families with MCD were studied. The genetic status of CHST6 was determined for all members of these MCD families. In addition, sulfated keratan sulfate (KS) assay from the probands was also undertaken. CHST6 gene was amplified by polymerase chain reaction (PCR). The PCR products were analyzed by sequencing and restriction digestion. Enzyme-linked immunosorbent assay (ELISA) was performed to assess KS presence in serum.

RESULTS

Four compound heterozygous mutations were identified, three of which are novel. The ELISA showed that the probands were of MCD type I.

CONCLUSIONS

These novel mutations are expected to result in loss of CHST6 function, which would account for the MCD phenotype.

BIGH3 mutation in a Bangladeshi family with a variable phenotype of LCDI

AIMS

To report a Bangladeshi family displaying intrafamilial phenotypic heterogeneity of lattice corneal dystrophy type I (LCDI) and to identify the causative mutation.

METHODS

Molecular genetic analysis was performed on DNA extracted from all members of the family. Exons of BIGH3 gene were amplified by polymerase chain reaction. Gene mutation and polymorphisms were identified by heteroduplex and sequence analyses. Segregation of the mutation in the family was confirmed by restriction digestion of amplified gene fragments.

RESULTS

A heterozygous C --> T transition at the first nucleotide position of codon 124 of the BIGH3 gene was detected in the three affected members and not in the unaffected members of the family.

CONCLUSIONS

This is the first report of BIGH3 gene mutation in a Bangladeshi family with phenotypic heterogeneity. This study confirms that BIGH3 gene screening should be undertaken for proper classification of corneal dystrophy, especially in the absence of histopathological examination.

A clinical, histopathological, and genetic study of Avellino corneal dystrophy in British families

AIMS

To establish a clinical, histopathological, and genetic diagnosis in two unrelated British families with Avellino corneal dystrophy (ACD).

METHODS

Genomic DNA was extracted from peripheral blood leucocytes of all members participating in the study. Exons 4 and 12 of the human transforming growth factor beta induced (BIGH3) gene were amplified by polymerase chain reaction. The mutation and polymorphism were identified by direct sequencing and restriction digest analysis. A review of the patients' clinical symptoms and signs was undertaken and a histopathological study on corneal specimen obtained from the proband of one family after keratoplasty was performed.

RESULTS

A heterozygous G to A transition at the second nucleotide position of codon 124 of BIGH3 gene was detected in all affected members of both families. This mutation changes an arginine residue to a histidine. The clinical diagnosis for ACD was more evident with advancing age. Histopathological study revealed granular deposits in the anterior stroma and occasional positive Congo red areas of amyloid deposition in the mid to deep stroma typical of ACD.

CONCLUSIONS

This is the first report of ACD families in the United Kingdom and, furthermore, of BIGH3 gene mutation in British patients with this rare type of corneal dystrophy. The results indicate that BIGH3 gene screening along with clinical and histopathological examinations is essential for the diagnosis and clinical management of corneal dystrophies.

Identification of novel mutations in the carbohydrate sulfotransferase gene (CHST6) causing macular corneal dystrophy

PURPOSE

Macular corneal dystrophy (MCD) is a rare corneal dystrophy that is characterized by abnormal deposits in the corneal stroma, keratocytes, Descemet's membrane, and endothelium, accompanied by progressive clouding. It has been classified into three immunophenotypes--MCD types I, IA, and II--according to the serum level of sulfated keratan sulfate (KS) and immunoreactivity of the corneal tissue. Recently, mutations in a new carbohydrate sulfotransferase gene (CHST6) encoding corneal glucosamine N-acetyl-6-sulfotransferase (C-GlcNac-6-ST) have been identified as the cause of MCD. Mutation screening of the CHST6 gene has been undertaken to identify the underlying mutations in five unrelated British families with MCD.

METHODS

DNA was extracted from venous blood obtained from all participants, and the coding region of CHST6 was amplified by polymerase chain reaction (PCR). The PCR products were analyzed by direct sequencing and restriction enzyme digestion. Enzyme-linked immunosorbent assay (ELISA) was performed to assess the presence of KS in serum from the probands of MCD-affected families participating in the study.

RESULTS

Six novel missense mutations--four homozygous and two compound heterozygous--were identified in the CHST6 gene. The ELISA showed that the disease in all patients participating in the study was of MCD type I, including the subtype IA.

CONCLUSIONS

These novel mutations are thought to result in loss of corneal sulfotransferase function, which would account for the MCD phenotype.