Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retinal dystrophy (Rdy) is an autosomal dominant photoreceptor dysplasia of Abyssinian cats and a model for autosomal dominant retinitis pigmentosa (ADRP) in man. We have pursued a candidate gene approach in the search for the causal mutation in Rdy. The genes RHO (encoding rhodopsin), ROM1 (encoding the structural retinal outer-membrane protein-1) and PDE6G (encoding the gamma subunit of the visual transduction protein cyclic guanosine monophosphate-phosphodiesterase) were polymerase chain reaction-amplified from normal feline genomic DNA. Leader, coding and 3' untranslated regions of each gene, and parts of introns were sequenced. Single-stranded conformation polymorphism (SSCP) analysis of Rdy-affected and normal cats was used to identify intragenic polymorphisms within ROM1 and PDE6G. DNA sequencing of all three genes in Rdy-affected cats was used to confirm results from SSCP. For both ROM1 and PDE6G polymorphisms identified by SSCP and sequencing showed disconcordance between the polymorphism and the disease phenotype within an Rdy disease pedigree. SSCP analysis of RHO performed across the 5' untranslated region, the entire coding sequence and the intron/exon boundaries in Rdy-affected and control cats failed to identify any intragenic polymorphisms that could be used for linkage analysis. DNA sequencing of these regions showed no differences between Rdy-affected and control cats. Mutations in ROM1 or in PDE6G are not causative of feline Rdy. The absence of potentially pathogenic polymorphisms in sequenced portions of the RHO gene makes it unlikely that a mutation in this gene is the cause of Rdy.
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PMID:Autosomal dominant retinal dystrophy (Rdy) in Abyssinian cats: exclusion of PDE6G and ROM1 and likely exclusion of Rhodopsin as candidate genes. 1246 18

The rd mouse has been widely used as an animal model of retinitis pigmentosa. In this model, a mutation of rod-specific phosphodiesterase leads to a loss of rods during the early period of postnatal life. Morphological modifications at the level of the outer plexiform layer have been shown (Proc. Nat. Acad. Sci. USA 97 (2000) 11020) in bipolar and horizontal cells. However, very little is known about the functional changes suffered by these cells postsynaptic to the degenerated rods. In the present work we have studied the neurotransmitter-induced currents in rod bipolar cells from the rd mouse retina. Currents induced by glutamate and GABA were studied by the patch clamp-whole cell technique, on rod bipolar cells enzymatically dissociated from the rd mouse retina. Data from rd animals were compared with non-dystrophic NMRI mice. GABA (30-100 micro M) and glutamate (100 micro M) were applied from a puff pipette in the near proximity of rod bipolar cell dendrites, clamped at physiological membrane potentials, and their evoked currents were studied. In rod bipolar cells from non-dystrophic mouse, puff application of glutamate induced an outward current. This current was increased twofold in absence of extracellular calcium (nominally 0 calcium). In rod bipolar cells from adult rd mouse, currents induced by glutamate were absent. Two types of GABA mediated currents were isolated in rod bipolar cells both in control and rd mouse retinas. The currents mediated by GABA(C) receptors were observed exclusively at the axon terminal, while the currents mediated by the GABA(A) receptors were observed upon GABA application to the bipolar cell dendrites. The currents mediated by GABA(A) receptors in rod bipolar cells from rd mouse were larger than those from control animals. We conclude that after the degeneration of rod photoreceptors in rd mouse, rod bipolar cells lost their glutamate (rod-neurotransmitter) input while they increase their response to GABA (horizontal cell-neurotransmitter). In our opinion, this work describes for the first time the changes in neurotransmitter sensitivity that affect rod bipolar cells after photoreceptor degeneration of the mouse retina.
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PMID:Functional modifications in rod bipolar cells in a mouse model of retinitis pigmentosa. 1266 57

The primary aim of gene transfer into the retinal cells has been to investigate the developmental mechanisms of the retinal cells or to reverse retinal diseases. Retroviruses have been used to investigate the differentiation of retinal cells, to study the embryonic retina in vivo or explant organ culture, and to trace the fate of the cells that were dividing at the time of gene transfer. Using adenovirus, Bennett et al. showed the possibility of using gene therapy to correct degenerative diseases of the central nervous system (CNS) (6). However, owing to the short duration of the gene expression, adenovirus is not suitable for correcting chronic diseases. Currently, lentivirus (7-9) and adenoassociated virus vectors (10-14) are being used for studying and correcting gene therapy of retinal degenerative diseases. Using an HIV vector carrying the green fluorescent protein (GFP) gene expressed from the cytomegalovirus (CMV) promoter, we showed that efficient and long-lasting gene expression could be obtained in the retina (7,8). Moreover, gene expression was restricted to the photoreceptor cells and was more efficient with the rhodopsin promoter. Similar results were reported using adeno-associated virus (AAV) vector. Using a lentivirus vector carrying the phosphodiesterase beta subunit (PDEbeta) gene, the mutation of which causes retinal degeneration called retinitis pigmentosa in rd mice, photoreceptor cells were rescued from degeneration in rd mice for at least 6 mo by PDEbeta transduction using HIV-based lentivirus vector (9).
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PMID:Delivery of genes to the eye using lentiviral vectors. 1497 Jun 9

The rd mouse, an accepted animal model for photoreceptor degeneration in retinitis pigmentosa, has a recessive mutation for the gene encoding the beta-subunit of the cGMP phosphodiesterase. This mutation results in high levels of cGMP, which leaves an increased number of the cGMP-gated channels in the open state, thus allowing intracellular calcium (Ca(2+)) to rise to toxic levels, and rapid photoreceptor degeneration follows. To delineate the events in rd photoreceptor degeneration, we demonstrated an increase in calpain and caspase-3 activity, hypothesizing that Ca(2+)-mediated apoptosis in photoreceptors is mediated by calpain, involving mitochondrial depolarization and caspase-3 activation. To examine this hypothesis further, a murine photoreceptor-derived cell line (661W) was treated with the Ca(2+) ionophore A23187, cGMP-gated channel agonist 8-bromo-cGMP, or phosphodiesterase inhibitor isobutylmethylxanthine to mimic the increased Ca(2+) influx seen in the rd photoreceptors. Ca(2+)-induced cell death in 661W cells was found to be mediated by calpain and caspase-3 and could be completely inhibited by the calpain inhibitor SJA6017, implicating both calpain and caspases in the apoptotic process. The apoptotic events correlated in an SJA6017-inhibitable manner with bid cleavage, mitochondrial depolarization, cytochrome c release, and caspase-3 and -9 activation. We concluded that Ca(2+) influx in the rd model of photoreceptor degeneration leads to the activation of the cysteine protease calpain, which executes apoptosis via modulation of caspase-3 activity.
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PMID:Calcium-induced calpain mediates apoptosis via caspase-3 in a mouse photoreceptor cell line. 2880 51

Naturally occurring mutations of the beta subunit of the cyclic guanosine monophosphate (cGMP) phosphodiesterase (beta-PDE) gene in rod photoreceptors of mice and dogs are similar to one of the inherited retinal degenerations termed retinitis pigmentosa in humans. Defects in the rod beta-PDE gene leading to photoreceptor cell degeneration in retinal degenerative (rd) mice can be corrected by transfer of a wild type beta-PDE gene. However, the rapid photoreceptor degeneration in this mutant makes the study of gene therapy difficult. Since the retinal degeneration is slowed in vitro, we have employed retinal explants from rd mice to study factors influencing viral transduction. Retinal explants provide a rapid, efficient method to compare the transduction efficiency of adenoviral vector-mediated reporter gene delivery at different ages in normal and rd mice. Retinal explants from postnatal day (P)2 to P28 control (C57BL/6J) and P2-P42 rd mice were exposed for 20 hr to 2.5 x 10(8) plaque forming units (pfu) ml(-1) of adenoviral vector with a beta-galactosidase (Lac Z) reporter gene (Ad-CMV-Lac Z). After incubation in vector-free media for an additional 3 days, the explants were fixed and histochemically stained for beta-galactosidase to reveal Lac Z gene expression. The explants were also embedded and sectioned for light microscopic observation. Transduction efficiency was higher in rd mice than in controls on all postnatal days examined. In normal retinal explants, expression of the Lac Z gene increased from P2 to a peak around P7-P8, then decreased at subsequent ages; little transduction could be found after P17. In rd mice transduction efficiency of Ad-CMV-Lac Z increased from P2 to P7, decreased by P10 and increased again after P10. The most dramatic increase in the transduction efficiency occurred in the rd retina between P10 and P15 when Lac Z was intensely expressed throughout the retina. Microscopic examination of retinal sections revealed the types and distribution of Lac Z-positive cells responsible for the deep blue staining in the retinal whole mount. In normal and rd mice, Lac Z-positive cells were located throughout the retina. However, larger numbers of Lac Z-positive cells were present at all ages examined in retinal explants from rd mice compared to normal mice. These data indicate a difference in transduction efficiency between normal and rd mice, especially after P12, and suggest efficient adenovirus-mediated gene transfer is more attainable in developing or degenerating retina. Thus, transduction efficiency in rd mice depends on the relationship between development, maturation and the degenerative state of the photoreceptor cells.
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PMID:Adenoviral-mediated gene transfer to retinal explants during development and degeneration. 1532 66

Retinitis pigmentosa comprises a heterogeneous group of incurable progressive blinding diseases with unknown pathogenic mechanisms. The retinal degeneration 1 (rd1) mouse is a retinitis pigmentosa model that carries a mutation in a rod photoreceptor-specific phosphodiesterase gene, leading to rapid degeneration of these cells. Elucidation of the molecular differences between rd1 and healthy retinae is crucial for explaining this degeneration and could assist in suggesting novel therapies. Here we used high resolution proteomics to compare the proteomes of the rd1 mouse retina and its congenic, wild-type counterpart at postnatal day 11 when photoreceptor death is profound. Over 3000 protein spots were consistently resolved by two-dimensional gel electrophoresis and subjected to a rigorous filtering procedure involving computer-based spot analyses. Five proteins were accepted as being differentially expressed in the rd1 model and subsequently identified by mass spectrometry. The difference in one such protein, phosducin, related to an altered modification pattern in the rd1 retina rather than to changed expression levels. Additional experiments showed phosducin in healthy retinae to be highly phosphorylated in the dark- but not in the light-adapted phase. In contrast, rd1 phosducin was highly phosphorylated irrespective of light status, indicating a dysfunctional rd1 light/dark response. The increased rd1 phosducin phosphorylation coincided with increased activation of calcium/calmodulin-activated protein kinase II, which is known to utilize phosducin as a substrate. Given the increased rod calcium levels present in the rd1 mutation, calcium-evoked overactivation of this kinase may be an early and long sought for step in events leading to photoreceptor degeneration in the rd1 mouse.
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PMID:Differential modification of phosducin protein in degenerating rd1 retina is associated with constitutively active Ca2+/calmodulin kinase II in rod outer segments. 1625 86

Mutations in the beta-subunit of cGMP-phosphodiesterase (PDE6beta) can lead to either progressive retinal disease, such as human retinitis pigmentosa (RP), or stationary disease, such as congenital stationary night blindness (CSNB). Individuals with CSNB in the Rambusch pedigree were found to carry the H258N allele of PDE6B (MIM# 180072); a similar mutation was not found in RP patients. This report describes an individual carrying the H258N allele, who presented with generalized retinal dysfunction affecting the rod system and a locus of dysfunction at the rod-bipolar interface. Also described are preclinical studies in which transgenic mice with the H258N allele were generated to study the pathophysiological mechanisms of CSNB. While Pde6b(rd1)/Pde6b(rd1) mice have severe photoreceptor degeneration, as in human RP, the H258N transgene rescued these cells. The cGMP-PDE6 activity of dark-adapted H258N mice showed an approximate three-fold increase in the rate of retinal cGMP hydrolysis: from 130.1 nmol x min(-1) x nmol(-1) rhodopsin in wild-type controls to 319.2 nmol x min(-1) x nmol(-1) rhodopsin in mutants, consistent with the hypothesis that inhibition of the PDE6beta activity by the regulatory PDE6gamma subunit is blocked by this mutation. In the albino (B6CBA x FVB) F2 hybrid background, electroretinograms (ERG) from H258N mice were similar to those obtained from affected Rambusch family members, as well as humans with the most common form of CSNB (X-linked), demonstrating a selective loss of the b-wave with relatively normal a-waves. When the H258N allele was introduced into the DBA background, there was no evidence of selective reduction in b-wave amplitudes; rather a- and b-wave amplitudes were both reduced. Thus, factors other than the PDE6B mutation itself could contribute to the variance of an electrophysiological response. Therefore, caution is advisable when interpreting physiological phenotypes associated with the same allele on different genetic backgrounds. Nevertheless, such animals should be of considerable value in further studies of the molecular pathology of CSNB.
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PMID:Transgenic mice carrying the H258N mutation in the gene encoding the beta-subunit of phosphodiesterase-6 (PDE6B) provide a model for human congenital stationary night blindness. 1704 14

Retinal degeneration 10 (rd10) mice are a model of autosomal recessive retinitis pigmentosa (RP), identified by Chang et al. in 2002 (Vision Res. 42:517-525). These mice carry a spontaneous mutation of the rod-phosphodiesterase (PDE) gene, leading to a rod degeneration that starts around P18. Later, cones are also lost. Because photoreceptor degeneration does not overlap with retinal development, and light responses can be recorded for about a month after birth, rd10 mice mimic typical human RP more closely than the well-known rd1 mutants. The aim of this study is to provide a comprehensive analysis of the morphology and function of the rd10 mouse retina during the period of maximum photoreceptor degeneration, thus contributing useful data for exploiting this novel model to study RP. We analyzed the morphology and survival of retinal cells in rd10 mice of various ages with quantitative immunocytochemistry and confocal microscopy; we also studied retinal function with the electroretinogram (ERG), recorded between P18 and P30. We found that photoreceptor death (peaking around P25) is accompanied and followed by dendritic retraction in bipolar and horizontal cells, which eventually undergo secondary degeneration. ERG reveals alterations in the physiology of the inner retina as early as P18 (before any obvious morphological change of inner neurons) and yet consistently with a reduced band amplification by bipolar cells. Thus, changes in the rd10 retina are very similar to what was previously found in rd1 mutants. However, an overall slower decay of retinal structure and function predicts that rd10 mice might become excellent models for rescue approaches.
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PMID:Retinal organization in the retinal degeneration 10 (rd10) mutant mouse: a morphological and ERG study. 1711 72

We report the chromosomal localization, mutant gene identification, ophthalmic appearance, histology, and functional analysis of two new hereditary mouse models of retinal degeneration not having the Pde6brd1("r", "rd", or "rodless") mutation. One strain harbors an autosomal recessive mutation that maps to mouse chromosome 5. Sequence analysis showed that the retinal degeneration is caused by a missense point mutation in exon 13 of the beta-subunit of the rod cGMP phosphodiesterase (beta-PDE) gene (Pde6b). The gene symbol for this strain was set as Pde6brd10, abbreviated rd10 hereafter. Mice homozygous for the rd10 mutation showed histological changes at postnatal day 16 (P16) of age and sclerotic retinal vessels at four weeks of age, consistent with retinal degeneration. Retinal sections were highly positive for TUNEL and activated caspase-3 immunoreactivity, specifically in the outer nuclear layer (ONL). ERGs were never normal, but rod and cone ERG a- and b-waves were easily measured at P18 and steadily declined over 90% by two months of age. Protein extracts from rd10 retinas were positive for beta-PDE immunoreactivity starting at about the same time as wild-type (P10), though signal averaged less than 40% of wild-type. Interestingly, rearing rd10 mice in total darkness delayed degeneration for at least a week, after which morphological and functional loss progressed irregularly. With the second strain, a complementation test with rd1 mice revealed that the retinal degeneration phenotype observed represents a possible new allele of Pde6b. Sequencing demonstrated a missense point mutation in exon 16 of the beta-subunit of rod phosphodiesterase gene, different from the point mutations in rd1 and rd10. The gene symbol for this strain was set as Pde6bnmf137, abbreviated nmf137 hereafter. Mice homozygous for this mutation showed retinal degeneration with a mottled retina and white retinal vessels at three weeks of age. The exon 13 missense mutation (rd10) is the first known occurrence of a second mutant allele spontaneously arising in the Pde6b gene in mice and may provide a model for studying the pathogenesis of autosomal recessive retinitis pigmentosa (arRP) in humans. It may also provide a better model for experimental pharmaceutical-based therapy for RP because of its later onset and milder retinal degeneration than rd1 and nmf137.
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PMID:Two mouse retinal degenerations caused by missense mutations in the beta-subunit of rod cGMP phosphodiesterase gene. 1726 5

Retinitis pigmentosa (RP) is an inherited retinal degeneration characterized by nyctalopia, ring scotoma, and bone-spicule pigmentation of the retina. So far, no effective therapy has been found for RP. As a possible molecular etiology of RP, retina-specific gene deficits are most likely involved, but little has been identified in terms of intracellular mechanisms leading to retinal photoreceptor cell death at post-translational levels. In order to find an effective therapy for RP, we must look for underlying common mechanisms that are responsible for the development of RP, instead of designing a specific therapy for each of the RP types with different causes. Therefore, in the present study, several animal models with different causes of RP were studied, including (1)Royal College of Surgeons (RCS) rats with a deficit of retinal pigment epithelium (RPE) function caused by rhodopsin mutation; (2) P23H rats, (3) S334ter rats, (4) photo stress rats, (5) retinal degeneration (rd) mice with a deficit of phosphodiesterase(PDE) function; and (6) cancer-associated retinopathy (CAR) model rats with a deficit of recoverin-dependent photoreceptor adaptation function. In each of these models, the following assessments were made in order to elucidate common pathological mechanisms among the models: (1) retinal function assessed by electroretinogram (ERG), (2) retinal morphology, (3) retinoid analysis, (4) rhodopsin regeneration, (5) rhodopsin phosphorylation and dephosphorylation, and (6) cytosolic cGMP levels. We found that unregulated photoreceptor adaptation processes caused by an imbalance of rhodopsin phosphorylation and dephosphorylation caused retinal dysfunction leading to photoreceptor cell death. As possible candidate drugs for normalizing these retinal dysfunctions and stopping further retinal degeneration, nilvadipine, a Ca channel blocker, retinoid derivatives, and anthocyanine were chosen and tested to determine their effect on the above animal models with retinal degeneration. Nilvadipine showed beneficial effects against retinal degeneration in all models tested, but retinoid derivatives and anthocyanine showed these beneficial effects in only some models. Thus our present data allowed us to test the effectiveness of nilvadipine in the treatment of human RP patients.
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PMID:[New drug therapy for retinal degeneration]. 1824 May 99


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