Genetic networks controlling retinal injury.

PURPOSE: The present study defines genomic loci underlying coordinate changes in gene expression following retinal injury. METHODS: A group of acute phase genes expressed in diverse nervous system tissues was defined by combining microarray results from injury studies from rat retina, brain, and spinal cord. Genomic loci regulating the brain expression of acute phase genes were identified using a panel of BXD recombinant inbred (RI) mouse strains. Candidate upstream regulators within a locus were defined using single nucleotide polymorphism databases and promoter motif databases. RESULTS: The acute phase response of rat retina, brain, and spinal cord was dominated by transcription factors. Three genomic loci control transcript expression of acute phase genes in brains of BXD RI mouse strains. One locus was identified on chromosome 12 and was highly correlated with the expression of classic acute phase genes. Within the locus we identified the inhibitor of DNA binding 2 (Id2) as a candidate upstream regulator. Id2 was upregulated as an acute phase transcript in injury models of rat retina, brain, and spinal cord. CONCLUSIONS: We defined a group of transcriptional changes associated with the retinal acute injury response. Using genetic linkage analysis of natural transcript variation, we identified regulatory loci and candidate regulators that control transcript levels of acute phase genes

Emergent temporal signaling in human trabecular meshwork cells: role of TRPV4-TRPM4 interactions

Trabecular meshwork (TM) cells are phagocytic cells that employ mechanotransduction to actively regulate intraocular pressure. Similar to macrophages, they express scavenger receptors and participate in antigen presentation within the immunosuppressive milieu of the anterior eye. Changes in pressure deform and compress the TM, altering their control of aqueous humor outflow but it is not known whether transducer activation shapes temporal signaling. The present study combines electrophysiology, histochemistry and functional imaging with gene silencing and heterologous expression to gain insight into Ca2+ signaling downstream from TRPV4 (Transient Receptor Potential Vanilloid 4), a stretch-activated polymodal cation channel. Human TM cells respond to the TRPV4 agonist GSK1016790A with fluctuations in intracellular Ca2+ concentration ([Ca2+]i) and an increase in [Na+]i. [Ca2+]i oscillations coincided with monovalent cation current that was suppressed by BAPTA, Ruthenium Red and the TRPM4 (Transient Receptor Potential Melastatin 4) channel inhibitor 9-phenanthrol. TM cells expressed TRPM4 mRNA, protein at the expected 130-150 kDa and showed punctate TRPM4 immunoreactivity at the membrane surface. Genetic silencing of TRPM4 antagonized TRPV4-evoked oscillatory signaling whereas TRPV4 and TRPM4 co-expression in HEK-293 cells reconstituted the oscillations. Membrane potential recordings suggested that TRPM4-dependent oscillations require release of Ca2+ from internal stores. 9-phenanthrol did not affect the outflow facility in mouse eyes and eyes from animals lacking TRPM4 had normal intraocular pressure. Collectively, our results show that TRPV4 activity initiates dynamic calcium signaling in TM cells by stimulating TRPM4 channels and intracellular Ca2+ release. It is possible that TRPV4-TRPM4 interactions downstream from the tensile and compressive impact of intraocular pressure contribute to homeostatic regulation and pathological remodeling within the conventional outflow pathway

A summary of the key attributes of light-induced retinal damage across the albino rat retina

The dorsoventral gradient of alterations manifested over time. At late stages, normal retina is restricted to ventral retina near the ora terminalis. The bulk of intact retina is () survivor retina with shortened photoreceptors. At early stages, zones of () stressed retina with stressed photoreceptors are large but then contract to a thin rim near the light damage (LD) margin. Also at early stages, transient buckling () appears at the junction of intact retina and the LD margin () as photoreceptors continue to produce outer segment material, but retinal pigmented epithelium (RPE) cells are compromised. LD retina forms () remodeling zones with internal revisions such as neuronal migration, microneuromas and fluid channel formation; () emigration sites with aggressive migration of retina cells into the remnant choroid, leaving behind decimated zones with severely depleted retinas. Abbreviations: BCs represents bipolar cells, ACs represents amacrine cells, GCs represents ganglion cells, CC represents choriocapillaris, MCs represents Müller cells.<p><b>Copyright information:</b></p><p>Taken from "Extreme retinal remodeling triggered by light damage: implications for age related macular degeneration"</p><p></p><p> 2008;14():782-805.</p><p>Published online 25 Apr 2008</p><p>PMCID:PMC2375357.</p><p></p

Glutamine profiles across the Survivor-light damage (LD)-Decimation gradient

Visualization: Quantitative gray-scale images of glutamine signals displayed as intensity. Up arrows, remnant retina-choroid interface; downward arrow is the small high glutamine seal region. The bottom panel is 0.579 mm wide and shows isolated glutamine gradients in retina, retinal pigment epithelium (RPE), choroid, seal, emigrant and decimated zones. All decimated zones show large numbers of holes (see Methods). Sample metadata: SD Rat, age at LX 60 d, animal #P240–2L-24, left eye, 24 h LX, harvested at 240 days pLX, bloc code 6685, slide code 3518.<p><b>Copyright information:</b></p><p>Taken from "Extreme retinal remodeling triggered by light damage: implications for age related macular degeneration"</p><p></p><p> 2008;14():782-805.</p><p>Published online 25 Apr 2008</p><p>PMCID:PMC2375357.</p><p></p

Γ-aminobutyric acid (GABA) profiles across the survivor-light damage (LD)-Decimation gradient

Visualization: Quantitative gray-scale images of GABA signals displayed as intensity. Boxes denotes large aggregates of emigrant GABA+ cells and processes in the decimated zone. The panel is 0.779 mm wide. Note the severe loss of GABA signals in the decimation zone. Sample metadata: SD Rat, age at LX 60 d, animal #P240–2L-24, left eye, 24 h LX, harvested at 240 days pLX, bloc code 6685, slide code 3518.<p><b>Copyright information:</b></p><p>Taken from "Extreme retinal remodeling triggered by light damage: implications for age related macular degeneration"</p><p></p><p> 2008;14():782-805.</p><p>Published online 25 Apr 2008</p><p>PMCID:PMC2375357.</p><p></p

Glutamine and cytosolic retinal binding protein (CRALBP) gradients in survivor, light damage, and decimated retina

Visualization: Quantitative gray-scale images of molecular signals displayed as intensity. Boxes indicate selected regions illustrating characteristic local features. The data set derives from a single 200 nm section over 5 mm long; segments between 0.496 and 4.46 mm are shown. 0.496–0.893 mm: Ventral survivor retina displays normal cytosolic retinal binding protein (CRALBP) and glutamine signatures. Rod opsin signals of boxed region are shown in panel 1.249–1.787 mm: Central survivor-light damage (LD) transition (upward arrow) shows Müller cell (MC) hypertrophy and elevated distal seal CRALBP and glutamine signals in LD zone. Rod opsin signals of boxed region are shown in panel Upward arrow denotes seal border. 1.888–2.774 mm: Dorsal LD retina has a nearly confluent seal with focal emigration clusters. CRALBP and glutamine signals of early emigrant cells are compared in panels 3.520–4.460 mm: Dorsal decimated retina shows loss of the glutamine seal and massive emigration. Over 50% of the retinal mass has moved into the choroid. CRALBP and glutamine signals of late emigrant cells are compared in panels and : Rod opsin rhodopsin 1D4 in survivor retina B: Rod opsin rhodopsin 1D4 in LD retina : CRALBP in early emigrant cells of LD zone. Upward arrows denote seal. Glutamine in early emigrant cells of LD zone. Upward arrows denote seal. CRALBP signals are depressed in late emigrant cells of LD zone. Downward arrows denote seal. Glutamine signals remain high in late emigrant cells of LD zone. Downward arrows denote seal. Sample metadata: SD Rat, age at LX 60 d, animal #P180–2R-48–120, right eye, 48 h LX, harvested at 120 days pLX, bloc code 6627, slide code 5223.<p><b>Copyright information:</b></p><p>Taken from "Extreme retinal remodeling triggered by light damage: implications for age related macular degeneration"</p><p></p><p> 2008;14():782-805.</p><p>Published online 25 Apr 2008</p><p>PMCID:PMC2375357.</p><p></p