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Anand Swaroop

Publications and source records attributed to Anand Swaroop.

At least 55 records · Page 3Linked to original sources
PubMed2004

Age-related macular degeneration: a high-resolution genome scan for susceptibility loci in a population enriched for late-stage disease.

Age-related macular degeneration (AMD) is a complex multifactorial disease that affects the central region of the retina. AMD is clinically heterogeneous, leading to geographic atrophy (GA) and/or choroidal neovascularization (CNV) at advanced stages. Considerable data exists in support of a genetic predisposition for AMD. Recent linkage studies have provided evidence in favor of several AMD susceptibility loci. We have performed a high-resolution (5-cM) genome scan of 412 affected relative pairs that were enriched for late-stage disease (GA and/or CNV). Nonparametric linkage analysis was performed using two different diagnostic criteria and also by dividing the affected individuals according to GA or CNV phenotype. Our results demonstrate evidence of linkage in regions that were suggested in at least one previous study at chromosomes 1q (236-240 cM in the Marshfield genetic map), 5p (40-50 cM), and 9q (111 cM). Multipoint analysis of affected relatives with CNV provided evidence of additional susceptibility loci on chromosomes 2p (10 cM) and 22q (25 cM). A recently identified Gln5345Arg change in HEMICENTIN-1 on chromosome 1q25 was not detected in 274 affected members in the restricted group with AMD, 346 additional patients with AMD, and 237 unaffected controls. Our results consolidate the chromosomal locations of several AMD susceptibility loci and, together with previous reports, should facilitate the search for disease-associated sequence variants.

Aging↗
PubMed2004

Mutation analysis of NR2E3 and NRL genes in Enhanced S Cone Syndrome.

Ten new and seventeen previously reported Enhanced S Cone Syndrome (ESCS) subjects were used to search for genetic heterogeneity. All subjects were diagnosed with ESCS on the basis of clinical, psychophysical and/or electroretinography testing using published criteria. Mutation analysis was performed on the NR2E3 nuclear receptor gene by single strand conformation analysis and direct sequencing, which revealed either homozygous (N=13) or compound heterozygous (N=11) mutations in 24 subjects (89%), heterozygous mutations in 2 subjects (7%) and no mutations in 1 subject (4%). Fifteen different mutations were identified, including six not previously reported. The subject (Patient A) with no detected NR2E3 mutation had features not usually associated with ESCS, in particular moderate rod photoreceptor function in peripheral retina and an abnormally thick retinal nerve fibre layer. Mutation analysis of the NRL, CRX, NR1D1 and THRB genes in this individual revealed a heterozygous one base-pair insertion in exon 2 of the NRL gene, which results in a predicted truncation of the NRL protein. Loss-of-function NRL alleles have not been described previously in humans, but since the same mutation was present in unaffected family members, it raises the possibility that the abnormal ESCS phenotype in Patient A may result from a digenic mechanism, with a heterozygous NRL mutation and a mutation in another unknown gene.

Abnormalities, Multiple↗
PubMed2004

Transgenic mice expressing Cre-recombinase specifically in M- or S-cone photoreceptors.

PURPOSE: To establish lines of transgenic mice that express Cre-recombinase in M- or S-cone photoreceptors for generating cone photoreceptor-specific (conditional) mutants. METHODS: Five kilobases of 5' upstream sequence of the mouse red-green (M) opsin gene or 0.5 kb of the mouse blue (S) opsin gene was cloned into a Cre-expression plasmid. Transgenic mice were generated and characterized, and appropriate lines were established. The Cre-transgenic mice were crossed with ROSA26-lacZ mice (containing floxed beta-galactosidase gene) and analyzed to determine Cre-recombinase activity. RESULTS: Immunofluorescence study showed successful targeting of Cre-recombinase expression to cone photoreceptors. Double staining with anti-Cre antibody and anti-M- or anti-S-opsin antibody revealed specificity of Cre expression in M-opsin- and/or S-opsin-positive photoreceptors. Mating with ROSA26-lacZ mice demonstrated that Cre-recombinase was functionally active in M- or S-cones. CONCLUSIONS: Lines of transgenic mice that specifically express functional Cre-recombinase in M- or S-cones were established in this study. Because mutations in several widely expressed genes lead to photoreceptor degeneration, these transgenic mice should be valuable in generating conditional mutants to investigate the function of various genes specifically in cone photoreceptors.

Animals↗
PubMed2004

Association of apolipoprotein E alleles with susceptibility to age-related macular degeneration in a large cohort from a single center.

PURPOSE: To examine the effect of apolipoprotein E (APOE) alleles on age-related macular degeneration (AMD) risk and on age at diagnosis of AMD in a large patient cohort recruited from a single center. METHODS: The frequency of APOE alleles was analyzed in 632 unrelated AMD patients and 206 unrelated controls, all of whom were of white ancestry. The presence or absence of disease symptoms in all patients and controls was based on clinical examination and/or ophthalmic records. The association with APOE was explored in the context of AMD subtypes, family history status, possible interaction with smoking, and distribution of age at diagnosis of AMD. RESULTS: The frequency of the epsilon4 allele was significantly reduced in patients compared with controls (0.10 vs. 0.14, P < or = 0.02). Gender- and age-adjusted odds ratios indicated that epsilon4-carriers have significantly lower risk of developing AMD compared to epsilon3epsilon3 subjects (OR = 0.55, 95% CI: 0.37-0.82, P = 0.004). In the cohort, AMD patients with a positive family history exhibited a significant 3.5 years earlier age at diagnosis (P = 0.001); however, APOE alleles did not appear to modulate the age at diagnosis of AMD. CONCLUSIONS: The association between the APOE-epsilon4 allele and a reduced risk of AMD was established in a large cohort with sufficient statistical power. How distinct APOE alleles affect AMD susceptibility warrants further investigation.

Aged↗
PubMed2004

Expression of photoreceptor-specific nuclear receptor NR2E3 in rod photoreceptors of fetal human retina.

PURPOSE: To study the physiological function of NR2E3 and possible molecular mechanisms underlying enhanced short-wavelength cone syndrome (ESCS) pathogenesis in developing human retina, and to compare its expression to that of Neural Retina Leucine zipper (NRL), a transcription factor essential for rod differentiation. METHODS: Expression of NR2E3, a photoreceptor-specific orphan nuclear receptor, was examined in human retinas between fetal weeks (Fwk) 9 to 22 by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Both NR2E3 and NRL expression patterns were followed by immunocytochemistry. The human retina develops in a central to peripheral pattern, in which a protein may take weeks to be expressed throughout the entire retina. This allowed a detailed temporal analysis of NR2E3 and NRL expression. RESULTS: NR2E3 expression was detected shortly after the appearance of NRL in putative immature rods on the foveal edge at Fwk 11.7. Expression of both markers was maintained in rod opsin expressing fetal photoreceptors. NR2E3 expression was not detected in either long/medium- or short-wavelength cones. Its absence from cones was also supported by the position of labeled nuclei deep in the outer nuclear layer, and by the absence of NR2E3 from the fovea. CONCLUSIONS: A role for NR2E3 in the rod developmental pathway is suggested. The closely related expression patterns of NRL and NR2E3 supported an interactive function, where both transcription factors determine the rod fate and suppress immature rods from adopting the S-cone fate.

Basic-Leucine Zipper Transcription Factors↗
PubMed2004

Characterization of new transcripts enriched in the mouse retina and identification of candidate retinal disease genes.

PURPOSE: Most retinal disease genes are preferentially expressed in photoreceptors, the light-sensitive cells involved in phototransduction. In addition, some of the genes linked to retinal diseases are essential for normal retinal development. The goal of this study was to identify new transcripts enriched in photoreceptors involved in retinal development or diseases. METHODS: To isolate uncharacterized retinal transcripts, the bioinformatic method Digital Differential Display (DDD) was used. RNA in situ hybridization was used to characterize gene-expression patterns. RESULTS: Twenty-seven mouse ESTs highly represented in retinal libraries were identified. Eight ESTs were predominantly expressed in photoreceptors and/or in the retinal pigment epithelium (RPE), whereas transcripts for other ESTs were detected more ubiquitously in the retinal cells or abundantly in ganglion cells and/or the inner nuclear layer. Mapping of the corresponding human orthologues of the photoreceptor/RPE-enriched genes revealed that two of them are candidate disease genes for retinitis pigmentosa, loci RP22 and RP28. Both of these are predominantly expressed in rod photoreceptors. The candidate RP22 gene codes for a putative transmembrane protein showing homology to Cln8 (ceroid lipofuscinosis, neuronal 8), in which gene mutations are associated with photoreceptors degeneration in mice. Also identified were two genes expressed in photoreceptors that are candidate disease genes for recessive Bardet-Biedl syndrome type 3 (BBS3) and recessive ataxia with RP (AXPC1). CONCLUSIONS: This study demonstrates how bioinformatic analysis can be used to identify novel tissue-specific genes relevant to development and diseases.

Animals↗
PubMed2003

Annotation and analysis of 10,000 expressed sequence tags from developing mouse eye and adult retina.

BACKGROUND: As a biomarker of cellular activities, the transcriptome of a specific tissue or cell type during development and disease is of great biomedical interest. We have generated and analyzed 10,000 expressed sequence tags (ESTs) from three mouse eye tissue cDNA libraries: embryonic day 15.5 (M15E) eye, postnatal day 2 (M2PN) eye and adult retina (MRA). RESULTS: Annotation of 8,633 non-mitochondrial and non-ribosomal high-quality ESTs revealed that 57% of the sequences represent known genes and 43% are unknown or novel ESTs, with M15E having the highest percentage of novel ESTs. Of these, 2,361 ESTs correspond to 747 unique genes and the remaining 6,272 are represented only once. Phototransduction genes are preferentially identified in MRA, whereas transcripts for cell structure and regulatory proteins are highly expressed in the developing eye. Map locations of human orthologs of known genes uncovered a high density of ocular genes on chromosome 17, and identified 277 genes in the critical regions of 37 retinal disease loci. In silico expression profiling identified 210 genes and/or ESTs over-expressed in the eye; of these, more than 26 are known to have vital retinal function. Comparisons between libraries provided a list of temporally regulated genes and/or ESTs. A few of these were validated by qRT-PCR analysis. CONCLUSIONS: Our studies present a large number of potentially interesting genes for biological investigation, and the annotated EST set provides a useful resource for microarray and functional genomic studies.

Aging↗
PubMed2003

A comprehensive analysis of the expression of crystallins in mouse retina.

PURPOSE: Crystallins are expressed at high levels in lens fiber cells. Recent studies have revealed that several members of the alpha, beta, and gamma-crystallin family are also distributed in many non-lens tissues, though at lower levels. We observed that the use of retinal RNA as target for both custom I-Gene microarrays and Affymetrix GeneChips revealed significant expression of many crystallin genes. This prompted us to undertake a comprehensive investigation to delineate the baseline expression of crystallin genes in the adult mouse retina. METHODS: Quantitative RT-PCR was carried out using gene specific primers (derived from the mouse genomic sequence) for each crystallin gene. Immunofluorescence studies using frozen sections of the mouse retinas were performed with crystallin-specific antibodies. Retinal lysates were analyzed by immunoblotting using antibodies specific to alphaA and alphaB crystallins and those produced against total beta-crystallin and gamma-crystallin fractions of bovine lenses. RESULTS: Microarray analysis followed by quantitative RT-PCR revealed that mouse retinal cells express transcripts for 20 different members of the crystallin gene family; these are alphaA, alphaA-INS, alphaA-nov1, alphaB, betaA1, betaA2, betaA3, betaA4, betaB1, betaB2, betaB3, gammaA, gammaC, gammaD, gammaE, gammaF, gammaS, mu, zeta, and lambda-crystallin. The gene products of alphaA, alphaB, beta-, and gamma-crystallins are detected in the outer and inner nuclear layers of the retina by immunofluorescence analysis. In addition, alpha and beta-crystallins are detected in the photoreceptor inner segments. Retinal expression of these proteins was further confirmed by immunoblot analysis. Interestingly, our studies also showed a significant animal-to-animal variation in the expression level of some of the crystallins. CONCLUSIONS: Our results establish the expression of many crystallins in the adult mouse retina. Detection of crystallins in the retinal nuclear layers, though surprising, is consistent with their proposed role in cell survival and genomic stability. We suggest that crystallins play vital functions in protecting retinal neurons from damage by environmental and/or metabolic stress.

Animals↗
PubMed2003

Mutation in a short-chain collagen gene, CTRP5, results in extracellular deposit formation in late-onset retinal degeneration: a genetic model for age-related macular degeneration.

A primary feature of age-related macular degeneration (AMD) is the presence of extracellular deposits between the retinal pigment epithelium (RPE) and underlying Bruch's membrane, leading to RPE dysfunction, photoreceptor death and severe visual loss. AMD accounts for about 50% of blind registrations in Western countries and is a common, genetically complex disorder. Very little is known regarding its molecular basis. Late-onset retinal degeneration (L-ORD) is an autosomal dominant disorder with striking clinical and pathological similarity to AMD. Here we show that L-ORD is genetically heterogeneous and that a proposed founder mutation in the CTRP5 (C1QTNF5) gene, which encodes a novel short-chain collagen, changes a highly conserved serine to arginine (Ser163Arg) in 7/14 L-ORD families and 0/1000 control individuals. The mutation occurs in the gC1q domain of CTRP5 and results in abnormal high molecular weight aggregate formation which may alter its higher-order structure and interactions. These results indicate a novel disease mechanism involving abnormal adhesion between RPE and Bruch's membrane.

Age of Onset↗
PubMed2003

GRK1-dependent phosphorylation of S and M opsins and their binding to cone arrestin during cone phototransduction in the mouse retina.

The shutoff mechanisms of the rod visual transduction cascade involve G-protein-coupled receptor (GPCR) kinase 1 (GRK1) phosphorylation of light-activated rhodopsin (R*) followed by rod arrestin binding. Deactivation of the cone phototransduction cascade in the mammalian retina is delineated poorly. In this study we sought to explore the potential mechanisms underlying the quenching of the phototransduction cascade in cone photoreceptors by using mouse models lacking rods and/or GRK1. Using the "pure-cone" retinas of the neural retina leucine zipper (Nrl) knock-out (KO, -/-) mice (Mears et al., 2001), we have demonstrated the light-dependent, multi-site phosphorylation of both S and M cone opsins by in situ phosphorylation and isoelectric focusing. Immunoprecipitation with affinity-purified polyclonal antibodies against either mouse cone arrestin (mCAR) or mouse S and M cone opsins revealed specific binding of mCAR to light-activated, phosphorylated cone opsins. To elucidate the potential role of GRK1 in cone opsin phosphorylation, we created Nrl and Grk1 double knock-out (Nrl-/-Grk1-/-) mice by crossing the Nrl-/- mice with Grk1-/- mice (Chen et al., 1999). We found that, in the retina of these mice, the light-activated cone opsins were neither phosphorylated nor bound with mCAR. Our results demonstrate, for the first time in a mammalian species, that cone opsins are phosphorylated and that CAR binds to phosphorylated cone opsins after light activation.

Animals↗
PubMed2003

Interaction of retinal bZIP transcription factor NRL with Flt3-interacting zinc-finger protein Fiz1: possible role of Fiz1 as a transcriptional repressor.

NRL (neural retina leucine zipper) is a basic motif leucine zipper transcription factor of the Maf-subfamily. Multiple phosphorylated isoforms of NRL are detected specifically in rod photoreceptors. NRL regulates the expression of several rod-specific genes, including rhodopsin and cGMP phosphodiesterase beta-subunit, in synergy with other transcription factors (e.g. the homeodomain protein CRX). Missense mutations in the human NRL gene are associated with autosomal dominant retinitis pigmentosa, whereas the loss of its function leads to rodless retina in Nrl-knockout mice that exhibit enhanced S-cone function. To further elucidate the molecular mechanism(s) underlying NRL-mediated transcriptional regulation, we used yeast two-hybrid screening to isolate NRL-interacting proteins in the retina and report the identification of Flt3-interacting zinc-finger protein, Fiz1. Interaction of Fiz1 and NRL-leucine zipper was validated by GST pulldown assays and co-immunoprecipitation from bovine retinal nuclear extracts. Fiz1 suppressed NRL- but not CRX-mediated transactivation of rhodopsin promoter activity in transiently transfected CV1 cells. The mRNA and the protein for both Fiz1 and its only other known interacting protein Flt3, a receptor tyrosine kinase, are expressed in the retina. Our results indicate potential cross-talk among signaling pathways in the retina and suggest that the function of NRL is modulated by its interaction with specific repressor proteins.

Amino Acid Sequence↗
PubMed2003

Mutation screening of patients with Leber Congenital Amaurosis or the enhanced S-Cone Syndrome reveals a lack of sequence variations in the NRL gene.

PURPOSE: To determine if mutations in the retinal transcription factor gene NRL are associated with retinopathies other than autosomal dominant retinitis pigmentosa (adRP). METHODS: Genomic DNA was isolated from blood samples obtained from 50 patients with Leber Congenital Amaurosis (LCA), 17 patients with the Enhanced S-Cone Syndrome (ESCS), and a patient with an atypical retinal degeneration that causes photoreceptor rosettes with blue cone opsin. The 5' upstream region (putative promoter), untranslated exon 1, coding exons 2 and 3, and exon-intron boundaries of the NRL gene were analyzed by direct sequencing of the PCR-amplified products. RESULTS: Complete sequencing of the NRL gene in DNA samples from this cohort of patients revealed only one nucleotide change. The C->G transversion at nucleotide 711 of NRL exon 3 was detected in one LCA patient; however, this change did not alter the amino acid (L237L). CONCLUSIONS: No potential disease causing mutation was identified in the NRL gene in patients with LCA, ESCS, or the atypical retinal degeneration. Together with previous studies, our results demonstrate that mutations in the NRL gene are not a major cause of retinopathy. To date, only missense changes have been reported in adRP patients, and sequence variations are rare. It is possible that the loss of NRL function in humans is associated with a more complex clinical phenotype due to its expression in pineal gland in addition to rod photoreceptors.

Basic-Leucine Zipper Transcription Factors↗
PubMed2003

Clinical studies of X-linked retinitis pigmentosa in three Swedish families with newly identified mutations in the RP2 and RPGR-ORF15 genes.

PURPOSE: To describe new disease-causing RP2 and RPGR-ORF15 mutations and their corresponding clinical phenotypes in Swedish families with X-linked retinitis pigmentosa (XLRP) and to establish genotype-phenotype correlations by studying the clinical spectrum of disease in families with a known molecular defect. METHODS: Seventeen unrelated families with RP and an apparent X-linked pattern of disease inheritance were identified from the Swedish RP registry and screened for mutations in the RP2 and RPGR (for the RP3 disease) genes. These families had been previously screened for the RPGR exons 1-19, and disease-causing mutations were identified in four of them. In the remaining 13 families, we sequenced the RP2 gene and the newly discovered RPGR-ORF exon. Detailed clinical evaluations were then obtained from individuals in the three families with identified mutations. RESULTS: Mutations in RP2 and RPGR-ORF15 were identified in three of the 13 families. Clinical evaluations of affected males and carrier females demonstrated varying degrees of retinal dysfunction and visual handicap, with early onset and severe disease in the families with mutations in the ORF15 exon of the RPGR gene. CONCLUSIONS: A total of seven mutations in the RP2 and RPGR genes have been discovered so far in Swedish XLRP families. All affected individuals express a severe form of retinal degeneration with visual handicap early in life, although the degree of retinal dysfunction varies both in hemizygous male patients and in heterozygous carrier females. Retinal disease phenotypes in patients with mutations in the RPGR-ORF15 were more severe than in patients with mutations in RP2 or other regions of the RPGR.

Adult↗
PubMed2003

De novo mutation in the RP1 gene (Arg677ter) associated with retinitis pigmentosa.

PURPOSE: The Arg677ter mutation in the RP1 gene is one of the most common causes of autosomal dominant retinitis pigmentosa (RP). In the current study, a de novo Arg677ter RP1 gene mutation was identified in a patient with RP. METHODS: RP1 gene mutation screening was performed in probands with simplex RP. In one proband with the RP1 mutation, paternity was established by analyzing 24 short tandem repeat polymorphisms. Additional candidate RP genes, including rhodopsin, RDS/peripherin, RP2, and RPGR, were also examined in this proband. Phenotype was characterized with psychophysics, electroretinography, and optical coherence tomography. RESULTS: An RP1 (Arg677ter) mutation was identified in one of the patients with simplex RP, but the sequence change was not detected in his parents. Parentage was confirmed, and other candidate genes were negative for mutations. Retinal function and cross-sectional imaging studies in the patient indicated greater rod than cone dysfunction with a photoreceptor basis for the abnormalities. CONCLUSIONS: The de novo origin of an RP1 (Arg677ter) mutation in a patient with simplex RP suggests that this common autosomal dominant RP mutation can arise independently in the population and supports the hypothesis of a mutational hotspot in the RP1 gene.

Adult↗
PubMed2002

Barrier to autointegration factor interacts with the cone-rod homeobox and represses its transactivation function.

Crx (cone-rod homeobox) is a homeodomain transcription factor implicated in regulating the expression of photoreceptor and pineal genes. To identify proteins that interact with Crx in the retina, we carried out a yeast two-hybrid screen of a retinal cDNA library. One of the identified clones encodes Baf (barrier to autointegration factor), which was previously shown to have a role in mitosis and retroviral integration. Additional biochemical assays provided supporting evidence for a Baf-Crx interaction. The Baf protein is detectable in all nuclear layers of the mouse retina, including the photoreceptors and the bipolar cells where Crx is expressed. Transient transfection assays with a rhodopsin-luciferase reporter in HEK293 cells demonstrate that overexpression of Baf represses Crx-mediated transactivation, suggesting that Baf acts as a negative regulator of Crx. Consistent with this role for Baf, an E80A mutation of CRX associated with cone-rod dystrophy has a higher than normal transactivation potency but a reduced interaction with Baf. Although our studies did not identify a causative Baf mutation in retinopathies, we suggest that Baf may contribute to the phenotype of a photoreceptor degenerative disease by modifying the activity of Crx. In view of the ubiquitous expression of Baf, we hypothesize that it may play a role in regulating tissue- or cell type-specific gene expression by interacting with homeodomain transcription factors.

Amino Acid Sequence↗
PubMed2002

Transcriptome analysis of the retina.

The retina offers unique opportunities to define the molecular and cellular pathways mediating neuronal function and disease because of its morphological complexity, well-defined role in visual transduction and the availability of mutants. These investigations are being greatly facilitated by the ongoing identification of genes expressed in the retina using high-throughput methods.

Animals↗