Publications by authors named "Beatrix Kovacs"

10 Publications

  • Page 1 of 1

Inactivation of the microRNA-183/96/182 cluster results in syndromic retinal degeneration.

Proc Natl Acad Sci U S A 2013 Feb 22;110(6):E507-16. Epub 2013 Jan 22.

Department of Pharmacology, Rush University Medical Center, Chicago, IL 60612, USA.

The microRNA-183/96/182 cluster is highly expressed in the retina and other sensory organs. To uncover its in vivo functions in the retina, we generated a knockout mouse model, designated "miR-183C(GT/GT)," using a gene-trap embryonic stem cell clone. We provide evidence that inactivation of the cluster results in early-onset and progressive synaptic defects of the photoreceptors, leading to abnormalities of scotopic and photopic electroretinograms with decreased b-wave amplitude as the primary defect and progressive retinal degeneration. In addition, inactivation of the miR-183/96/182 cluster resulted in global changes in retinal gene expression, with enrichment of genes important for synaptogenesis, synaptic transmission, photoreceptor morphogenesis, and phototransduction, suggesting that the miR-183/96/182 cluster plays important roles in postnatal functional differentiation and synaptic connectivity of photoreceptors.
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http://dx.doi.org/10.1073/pnas.1212655110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3568372PMC
February 2013

MicroRNAs in early diabetic retinopathy in streptozotocin-induced diabetic rats.

Invest Ophthalmol Vis Sci 2011 Jun 21;52(7):4402-9. Epub 2011 Jun 21.

Department of Ophthalmology and Neurological Sciences, Rush University Medical Center, Chicago, Illinois 60612, USA.

Purpose: Diabetic retinopathy (DR) is one of the leading causes of blindness. However, the roles of microRNAs (miRNAs) in DR are still unknown. The aims of this study were to identify miRNAs involved in early DR and to characterize their roles in the pathogenesis of DR.

Methods: miRNA-expression profiling was performed in the retina and retinal endothelial cells (RECs) of streptozotocin (STZ)-induced diabetic rats 3 months after the onset of diabetes and miRNAs differentially expressed in diabetic rats were identified and compared with controls. Subsequently, functional annotation analysis was conducted to identify miRNA signatures of pathologic pathways of DR. In addition, in vitro functional assays were used to dissect interactions of miR-146 and NF-κB activation in a conditionally immortalized retinal capillary endothelial cell line, Tr-iBRB.

Results: Approximately 350 and 220 miRNAs were detected in the retinas and RECs, respectively, in both control and diabetic rats. At least 86 and 120 miRNAs were differentially expressed (P < 0.01) in the retinas and RECs of diabetic rats and controls, respectively. Upregulation of NF-κB-, VEGF-, and p53-responsive miRNAs constituted key miRNA signatures, reflecting ongoing pathologic changes of early DR. In addition, it was demonstrated that the negative feedback regulation of miR-146 on NF-κB activation may function in Tr-iBRB endothelial cells, suggesting that miR-146 is a potential therapeutic target for the treatment of DR through its inhibition on NF-κB activation in RECs.

Conclusions: miRNAs are involved in the pathogenesis of DR through the modulation of multiple pathogenetic pathways and may be novel therapeutic targets for the treatment of DR.
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http://dx.doi.org/10.1167/iovs.10-6879DOI Listing
June 2011

Beta-amyloid deposition and functional impairment in the retina of the APPswe/PS1DeltaE9 transgenic mouse model of Alzheimer's disease.

Invest Ophthalmol Vis Sci 2009 Feb 12;50(2):793-800. Epub 2008 Sep 12.

Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA.

Purpose: To determine whether beta-amyloid (Abeta) deposition affects the structure and function of the retina of the APPswe/PS1DeltaE9 transgenic (tg) mouse model of Alzheimer's disease.

Methods: Retinas from 12- to 19-month old APPswe/PS1DeltaE9 tg and age-matched non-transgenic (ntg) littermates were single or double stained with thioflavine-S and antibodies against Abeta, glial fibrillar acidic protein (GFAP), microglial marker F4/80, choline acetyltransferase (ChAT), and syntaxin 1. Quantification of thioflavine-S positive plaques and retinal layer thickness was analyzed semi-quantitatively, whereas microglial cell size and levels of F4/80 immunoreactivity were evaluated using a densitometry program. Scotopic electroretinogram (ERG) recording was used to investigate retinal physiology in these mice.

Results: Thioflavine-S positive plaques appeared at 12 months in the retinas of APPswe/PS1DeltaE9 tg mice with the majority of plaques in the outer and inner plexiform layers. Plaques were embedded in the inner plexiform layer strata displaying syntaxin 1 and ChAT. The number and size of the plaques in the retina increased with age. Plaques appeared earlier and in greater numbers in females than in male tg littermate mice. Microglial activity was significantly increased in the retinas of APPswe/PS1DeltaE9 tg mice. Although we did not detect neuronal degeneration in the retina, ERG recordings revealed a significant reduction in the amplitudes of a- and b-waves in aged APPswe/PS1DeltaE9 tg compared to ntg littermates.

Conclusions: The present findings suggest that Abeta deposition disrupts retinal structure and may contribute to the visual deficits seen in aged APPswe/PS1DeltaE9 tg mice. Whether Abeta is involved in other forms of age-related retinal dysfunction is unclear.
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http://dx.doi.org/10.1167/iovs.08-2384DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3697019PMC
February 2009

MicroRNA (miRNA) transcriptome of mouse retina and identification of a sensory organ-specific miRNA cluster.

J Biol Chem 2007 Aug 27;282(34):25053-66. Epub 2007 Jun 27.

Department of Ophthalmology and Neurological Sciences, Rush University Medical Center, Chicago, Illinois 60302, USA.

Although microRNAs (miRNAs) provide a newly recognized level of regulation of gene expression, the miRNA transcriptome of the retina and the contributions of miRNAs to retinal development and function are largely unknown. To begin to understand the functions of miRNAs in retina, we compared miRNA expression profiles in adult mouse retina, brain, and heart by microarray analysis. Our results show that at least 78 miRNAs are expressed in adult mouse retina, 21 of which are potentially retina-specific. Among these, we identified a polycistronic, sensory organ-specific paralogous miRNA cluster that includes miR-96, miR-182, and miR-183 on mouse chromosome 6qA3 with conservation of synteny to human chromosome 7q32.2. In situ hybridization showed that members of this cluster are expressed in photoreceptors, retinal bipolar and amacrine cells. Consistent with their genomic organization, these miRNAs have a similar expression pattern during development with abundance increasing postnatally and peaking in adult retina. Target prediction and in vitro functional studies showed that MITF, a transcription factor required for the establishment and maintenance of retinal pigmented epithelium, is a direct target of miR-96 and miR-182. Additionally, to identify miRNAs potentially involved in circadian rhythm regulation of the retina, we performed miRNA expression profiling with retinal RNA harvested at noon (Zeitgeber time 5) and midnight (Zeitgeber time 17) and identified a subgroup of 12 miRNAs, including members of the miR-183/96/182 cluster with diurnal variation in expression pattern. Our results suggest that miR-96 and miR-182 are involved in circadian rhythm regulation, perhaps by modulating the expression of adenylyl cyclase VI (ADCY6).
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http://dx.doi.org/10.1074/jbc.M700501200DOI Listing
August 2007

The neural substrates of amphetamine conditioned place preference: implications for the formation of conditioned stimulus-reward associations.

Eur J Neurosci 2006 Oct;24(7):2089-97

Department of Cellular and Molecular Pharmacology, Rosalind Franklin University of Medicine and Science, Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA.

Associations formed between conditioned stimuli and drug reward are major contributors in human drug addiction. To better understand the brain changes that accompany this process, we used immunohistochemistry for c-Fos (a neuronal activity marker), synaptophysin (a marker for synaptogenesis) and tyrosine kinase B receptor (a neurotrophic factor receptor that mediates synaptic plasticity) to investigate the neural substrates of amphetamine-induced conditioned place preference in rats. Conditioned place preference was induced by both 1.0 mg/kg and 0.3 mg/kg doses of amphetamine. Furthermore, amphetamine conditioning increased the density of c-Fos-immunoreactive cells and these cells were fully colocalized with the tyrosine kinase B receptor in the dentate gyrus, CA1 field and basolateral amygdala. Amphetamine conditioning increased the density of synaptophysin-immunoreactive varicosities in all brain regions studied, except the nucleus accumbens shell and dorsolateral striatum. The degree of conditioned place preference was highly correlated with c-Fos-immunoreactive cell density in the basolateral amygdala and with the density of synaptophysin-immunoreactive varicosities in all mesolimbic regions studied. The latter correlation was particularly impressive for the ventral pallidum and basolateral amygdala. The formation of conditioned stimulus-amphetamine reward associations is accompanied by tyrosine kinase B receptor expression in the basolateral amygdala and dentate gyrus, CA1 and CA3 fields of the hippocampus. These data therefore suggest that the formation of conditioned stimulus-reward associations requires, at least in part, activation of amygdalar-hippocampal circuits.
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http://dx.doi.org/10.1111/j.1460-9568.2006.05066.xDOI Listing
October 2006

Effects of muscarinic antagonists on ZENK expression in the chicken retina.

Exp Eye Res 2006 Mar 6;82(3):379-88. Epub 2005 Sep 6.

Section for Neurobiology of the Eye, University Eye Hospital, Calwerstr. 7/1, 72076 Tuebingen, Germany.

Muscarinic antagonists, particularly atropine, can inhibit myopia development in several animal models and also in children. However, the biochemical basis of the inhibition of axial eye growth remains obscure, and there are doubts whether muscarinic receptors are involved at all. Experiments in chickens and monkeys have shown that the synthesis of the transcription factor ZENK, also named Egr-1, in retinal glucagon amacrine cells is strongly associated with inhibition of axial eye growth (assumed to create a STOP signal). We have tested whether the muscarinic antagonists atropine, pirenzepine, oxyphenonium, gallamine, MT-3, himbacine, and 4-DAMP can stimulate ZENK expression so that the drugs' inhibitory effect on myopia development could be explained by an enhanced STOP signal. Because it is known that intravitreal quisqualic acid (QA) eliminates most cholinergic neurons in the retina within 6 or 7 days, in a second set of experiments, we tested whether these antagonists could still stimulate ZENK production, 6 days after QA was applied. Muscarinic antagonists, injected intravitreally at various concentrations, affected ZENK synthesis in various and unpredictable ways. Pirenzepine, oxyphenonium, and MT-3 increased the proportion of glucagon cells that were ZENK-immunoreactive, whereas himbacine decreased that proportion, and gallamine and 4-DAMP had no significant effect. Atropine caused an upregulation of ZENK only if all positive amacrine and bipolar cells were counted and therefore appeared to affect primarily cells other than glucagon amacrines. The pattern of results remained unchanged after ablation of most cholinergic neurons by QA. Our results suggest that at least some muscarinic antagonists do not activate cells that synthesize ZENK when they inhibit axial eye growth. Therefore, in line with other studies they also cast doubt on the assumption that muscarinic transmission is crucial, and they suggest that muscarinic antagonists may inhibit myopia through extraretinal target sites or through non-cholinergic retinal actions.
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http://dx.doi.org/10.1016/j.exer.2005.07.010DOI Listing
March 2006

Calmodulin gene expression in the neural retina of the adult rat.

Life Sci 2003 Nov;73(25):3213-24

Department of Zoology and Cell Biology, University of Szeged, 2 Egyetem u., POB 659, Szeged, H-6722, Hungary.

Calmodulin (CaM) mRNAs are expressed with low abundancy in the adult rat neural retina. However, when digoxigenin (DIG)-labeled cRNA probes specific for each CaM mRNA population were hybridized at slightly alkaline pH (pH 8.0), the widespread distribution of CaM mRNA-expressing cells was revealed, with similar abundance for all three CaM genes. The CaM genes displayed a uniquely similar, layer-specific expression throughout the retina, and no significant differences were found in the distribution patterns of the CaM mRNA populations or the labeled cell types. The strongest signal for all CaM mRNAs was demonstrated in the ganglion cell layer and the inner nuclear layer, where the highest signal intensity was found within the inner sublamina. Similarly intermediate signal intensities for all CaM genes were detected in the inner and outer plexiform layers, within the vicinity of the outer limiting membrane and in the retinal pigment epithelium. A very low specific signal was characteristic in the outer nuclear layer and the photoreceptor inner segment layer, while no specific hybridization signal was observed in the photoreceptor outer segment layer. In summary, all CaM genes exhibited a similar and a characteristically layer-specific expression pattern in the adult rat retina.
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http://dx.doi.org/10.1016/j.lfs.2003.05.005DOI Listing
November 2003

Subgroup analysis of sex difference on the Vandenberg-Kuse mental rotation test.

Percept Mot Skills 2003 Feb;96(1):197-200

Institute of Behavior Sciences, Medical University of Pecs, Hungary.

A large sex difference has been elicited on the Vandenberg-Kuse mental rotation test. Prior research emphasizes the biological root of this sex difference. In recent experiments we confirmed this viewpoint. A large sample was administered the test, and the distributions of scores for men and women (N = 138; 68 men and 70 women: ages 19 to 23 years). The mean scores were used as cut-off points to group the men and the women in different subgroups (Low/Women, High/Women, Low/Men, High/Men). There were large differences among all subgroups, reinforcing Kimura's testosterone hypothesis for sex differences in spatial ability.
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http://dx.doi.org/10.2466/pms.2003.96.1.197DOI Listing
February 2003

Differential calmodulin gene expression in the rodent brain.

Life Sci 2002 May;70(24):2829-55

Department of Zoology and Cell Biology, University of Szeged, Hungary.

Apparently redundant members of the calmodulin (CaM) gene family encode for the same amino acid sequence. CaM, a ubiquitous cytoplasmic calcium ion receptor, regulates the function of a variety of target molecules even in a single cell. Maintenance of the fidelity of the active CaM-target interactions in different compartments of the cell requires a rather complex control of the total cellular CaM pool comprising multiple levels of regulatory circuits. Among these mechanisms, it has long been proposed that a multigene family maximizes the regulatory potentials at the level of the gene expression. CaM genes are expressed at a particularly profound level in the mammalian central nervous system (CNS), especially in the highly polarized neurons. Thus, in the search for clear evidence of the suggested differential expression of the CaM genes, much of the research has been focused on the elements of the CNS. This review aims to give a comprehensive survey on the current understanding of this field at the level of the regulation of CaM mRNA transcription and distribution in the rodent brain. The results indicate that the CaM genes are indeed expressed in a gene-specific manner in the developing and adult brain under physiological conditions. To establish local CaM pools in distant intracellular compartments (dendrites and glial processes), local protein synthesis from differentially targeted mRNAs is also employed. Moreover, the CaM genes are controlled in a unique, gene-specific fashion when responding to certain external stimuli. Additionally, putative regulatory elements have been identified on the CaM genes and mRNAs.
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http://dx.doi.org/10.1016/s0024-3205(02)01544-8DOI Listing
May 2002

Differential expression of multiple calmodulin genes in cells of the white matter of the rat spinal cord.

Brain Res Mol Brain Res 2002 Jun;102(1-2):28-34

Department of Zoology and Cell Biology, University of Szeged, 2 Egyetem u., P.O. Box 659, Szeged, Hungary.

Calmodulin (CaM) displays complex cytoplasmic and synaptic functions in the nervous system. However, the very little information that is available on the gene expression of the multiple CaM genes in different glial cell types are from brain tissues of rodents, and no data have been published on their CaM gene expression in the spinal cord. Therefore, we have modified and tested a color in situ hybridization method sensitive enough to detect mRNA populations in cells with low CaM mRNA abundances in the white matter of the rat lumbar spinal cord. Morphologically, two distinct cell types expressing CaM mRNAs were detected. Differential CaM gene expression was demonstrated in medium-sized astrocyte-like cells that reside predominantly in the dorsal column of the spinal cord, where CaM I mRNA was most abundant, followed by the CaM III and CaM II mRNA populations. The oligodendrocytes displayed a less differential CaM gene expression in both the dorsal and the lateral columns, but the CaM I gene had a slightly higher expression level than those of the other CaM genes. The results indicate that the CaM gene expression profile of the spinal cord is richer and more complex than previously thought on the basis of conventional radioactive in situ hybridization techniques. Thus, when a method that is sufficiently sensitive was used, more cell types could be demonstrated to express CaM mRNAs; hence, in spite of their lower CaM expression, glial cells could also be visualized.
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http://dx.doi.org/10.1016/s0169-328x(02)00159-6DOI Listing
June 2002
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