Identification of molecular markers of bipolar cells in the murine retina

Retinal bipolar neurons serve as relay interneurons that connect rod and cone photoreceptor cells to amacrine and ganglion cells. They exhibit diverse morphologies essential for correct routing of photoreceptor cell signals to specific postsynaptic amacrine and ganglion cells. The development and physiology of these interneurons have not been completely defined molecularly. Despite previous identification of genes expressed in several bipolar cell subtypes, molecules that mark each bipolar cell type still await discovery. In this report, novel genetic markers of murine bipolar cells were found. Candidates were initially generated by using microarray analysis of single bipolar cells and mining of retinal serial analysis of gene expression (SAGE) data. These candidates were subsequently tested for expression in bipolar cells by RNA in situ hybridization. Ten new molecular markers were identified, five of which are highly enriched in their expression in bipolar cells within the adult retina. Double-labeling experiments using probes for previously characterized subsets of bipolar cells were performed to identify the subtypes of bipolar cells that express the novel markers. Additionally, the expression of bipolar cell genes was analyzed in Bhlhb4 knockout retinas, in which rod bipolar cells degenerate postnatally, to delineate further the identity of bipolar cells in which novel markers are found. From the analysis of Bhlhb4 mutant retinas, cone bipolar cell gene expression appears to be relatively unaffected by the degeneration of rod bipolar cells. Identification of molecular markers for the various subtypes of bipolar cells will lead to greater insights into the development and function of these diverse interneurons

Early evolution of the LIM homeobox gene family

Background: LIM homeobox (Lhx) transcription factors are unique to the animal lineage and have patterning roles during embryonic development in flies, nematodes and vertebrates, with a conserved role in specifying neuronal identity. Though genes of this family have been reported in a sponge and a cnidarian, the expression patterns and functions of the Lhx family during development in non-bilaterian phyla are not known

Heterogeneity of Glia in the Retina and Optic Nerve of Birds and Mammals

We have recently described a novel type of glial cell that is scattered across the inner layers of the avian retina [1]. These cells are stimulated by insulin-like growth factor 1 (IGF1) to proliferate, migrate distally into the retina, and up-regulate the nestin-related intermediate filament transitin. These changes in glial activity correspond with increased susceptibility of neurons to excitotoxic damage. This novel cell-type has been termed the Non-astrocytic Inner Retinal Glia-like (NIRG) cells. The purpose of the study was to investigate whether the retinas of non-avian species contain cells that resemble NIRG cells. We assayed for NIRG cells by probing for the expression of Sox2, Sox9, Nkx2.2, vimentin and nestin. NIRG cells were distinguished from astrocytes by a lack of expression for Glial Fibrilliary Acidic Protein (GFAP). We examined the retinas of adult mice, guinea pigs, dogs and monkeys (Macaca fasicularis). In the mouse retina and optic nerve head, we identified numerous astrocytes that expressed GFAP, S100β, Sox2 and Sox9; however, we found no evidence for NIRG-like cells that were positive for Nkx2.2, nestin, and negative for GFAP. In the guinea pig retina, we did not find astrocytes or NIRG cells in the retina, whereas we identified astrocytes in the optic nerve. In the eyes of dogs and monkeys, we found astrocytes and NIRG-like cells scattered across inner layers of the retina and within the optic nerve. We conclude that NIRG-like cells are present in the retinas of canines and non-human primates, whereas the retinas of mice and guinea pigs do not contain NIRG cells

Tangential migration of corridor guidepost neurons contributes to anxiety circuits

In mammals, thalamic axons are guided internally towards their neocortical target by corridor (Co) neurons that act as axonal guideposts. The existence of Co-like neurons in non-mammalian species, in which thalamic axons do not grow internally, raised the possibility that Co cells might have an ancestral role. Here, we investigated the contribution of corridor (Co) cells to mature brain circuits using a combination of genetic fate-mapping and assays in mice. We unexpectedly found that Co neurons contribute to striatal-like projection neurons in the central extended amygdala. In particular, Co-like neurons participate in specific nuclei of the bed nucleus of the stria terminalis (BNST), which plays essential roles in anxiety circuits. Our study shows that Co neurons possess an evolutionary conserved role in anxiety circuits independently from an acquired guidepost function. It furthermore highlights that neurons can have multiple sequential functions during brain wiring and supports a general role of tangential migration in the building of subpallial circuits. This article is protected by copyright. All rights reserved

Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina

High-voltage-activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes, including the influx of extracellular Ca2+, neurotransmitter release, gene transcription, and synaptic plasticity. These channels consist of a primary α1 pore-forming subunit, which is associated with an extracellular α2δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α2δ3 subunit in the mouse and rat retina is unknown. In this study using RT-PCR, a single band at ∼305 bp corresponding to the predicted size of the α2δ3 subunit fragment was found in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123-kDa band. Immunohistochemistry with an affinity-purified antibody to the α2δ3 subunit revealed immunoreactive cell bodies in the ganglion cell layer and inner nuclear layer and immunoreactive processes in the inner plexiform layer and the outer plexiform layer. α2δ3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine, and bipolar cells and photoreceptors, but not horizontal cells. The expression of the α2δ3 calcium channel subunit to multiple cell types suggests that this subunit participates widely in Ca-channel-mediated signaling in the retina.U.S. Army Medical Research & Materiel Command (USAMRMC); Grant sponsor: Telemedicine & Advanced Technology Research Center (TATRC); Grant number: W81XWH-10-2-0077; Grant sponsor: National Institutes of Health; Grant number: EY04067; Grant sponsor: VA Merit Review (to N.B.)

The LIM-homeodomain protein islet-1 is a key regulator of restricted neuronal subtypes in the retina and forebrain

Thesis (Ph. D.)--University of Rochester. School of Medicine and Dentistry. Interdepartmental Graduate Program in Neuroscience, 2008.LIM-homeodomain proteins play important roles in neuronal differentiation and the establishment of neurotransmitter identity. Early lethality of loss-of-function mutants has hindered testing the role of many of these LIM-homeodomain proteins in later-developing CNS structures, such as the retina and forebrain. Thus, little is known about the role of this transcription factor class in retinal and forebrain development. Characterizing the expression of the LIM-homeodomain protein Islet-1 (Isl1) during retinal neurogenesis revealed the early expression of Isl1 during the ontogeny of three retinal cell types: bipolar interneurons, amacrine cells, and retinal ganglion cells. In the mature retina, Isl1 expression was restricted to ON-type bipolar interneurons, ganglion cells, and cholinergic amacrines. Similarly, in the adult striatum, Isl1 expression was restricted to cholinergic interneurons, and in the basal forebrain, Isl1 colocalized with many cholinergic projection neurons in the nucleus basalis. We report the function of Isl1 in retinal and forebrain development by conditionally deleting the Isl1 gene using an eye- and forebrain-specific Cre-expressing line, Six3-cre, and by assessing the histological and behavioral consequences of Isl1 deletion on CNS development and function. We report that deletion of Isl1 profoundly disrupts retinal function as assessed by electroretinograms and vision as assessed by optomotor behavior. These deficits are coupled with marked reductions in mature ON- and OFF-bipolar (>76%), cholinergic amacrine (93%), and ganglion (71%) cells. Spatiotemporal expression analysis of additional LIM-homeobox genes identifies a LIM-homeobox gene network during bipolar cell development that includes Lhx3 and Lhx4. Mosaic deletion of Isl1 demonstrates a cell-autonomous role for Isl1 in rod bipolar and cholinergic amacrine development. Cholinergic neuron development in the forebrain is also disrupted following Isl1 deletion. The depletion of cholinergic interneurons in the dorsal and ventral striatum and cholinergic projection neurons in the nucleus basalis observed is ascribed to an early and persistent defect in cholinergic neuron differentiation. Notably, cholinergic innervation to the neocortex is abolished, while that to the hippocampus is unaltered, consistent with the trajectories of cholinergic projection neurons disrupted in Isl1 conditional knockouts. Together, these results demonstrate the requirement for Isl1 in the development of distinct retinal and forebrain neuron subtypes, and link the development of cholinergic neurons in anatomically disparate sites to Isl1 function

Outcomes of Gallic Acid on Alternariol Induced Cyto-Morphic and Genotoxic In Vivo Changes in Parotid Gland: 4-HNE Incorporated

Alternaria toxins are emerging mycotoxins that gained considerable interest with increasing evidence of their existence and toxicological properties. There is limited research and insufficient data about their in vivo hazardous effects. We designed this study to evaluate histopathological and genotoxic in vivo impacts of alternariol (AOH) on the parotid gland as well as to assess the competency of gallic acid (GA) in reversing these effects. Forty healthy adult male Wister rats were utilized and assigned equally on control, GA, alternariol and AOH+ gallic treated groups. Parotid gland samples from experimental groups were collected and then examined for histopathological, ultrastructural and immunohistochemical examination for 4-hydroxynonenal “4-HNE as lipid peroxidation marker” as well as Comet assay for DNA damage. Additionally, parotid tissue homogenates were tested for catalase “CAT”, superoxide dismutase “SOD” and malondialdehyde “MDA” levels. Our data proved that alternariol produced various histopathological and ultrastructural alterations of parotid acini as well as significant DNA damage, significant reduction of CAT and SOD enzymatic activity and significant boosting of 4-HNE immunohistochemical expression and MDA levels as compared to control group. On the other hand, gallic acid administration almost restored histological and ultrastructural parotid architecture, 4-HNE immune-expression and biochemical levels. Ultimately, we demonstrated alternariol-induced histopathological and genotoxic alterations on parotid gland as well as the competency of gallic acid in reversing these effects

Islet-1 Controls the Differentiation of Retinal Bipolar and Cholinergic Amacrine Cells

West elevation, detail of the corner, depicting corner stair; On 16 October 1834, most of the Palace was destroyed by fire. Only Westminster Hall, the Jewel Tower, the crypt of St Stephen's Chapel and the cloisters survived. A Royal Commission was appointed to study the rebuilding of the Palace and decided that it should be rebuilt on the same site, and that its style should be either Gothic or Elizabethan. A heated public debate over the proposed styles ensued. It was decided that neo-Classical design, similar to that of the White House and Congress in the USA, was to be avoided due to its connotations of revolution and republic. Gothic design embodied conservative values. "On 29 February 1836 the first premium was given to Barry. The great task of rebuilding the Palace was to occupy him for the rest of his life. At his death it was still unfinished and was continued by his son E. M. Barry until 1870. The remarkable features of Barry's design were its confident Gothic detail and ingenious plan, which brilliantly incorporated the remaining medieval buildings into a logical system of circulation. Barry constantly revised and improved his design so that the final result became a uniquely successful masterpiece, which, although in the Gothic style, was designed on classical principles with a system of repeating modules." Source: Grove Art Online; http://www.groveart.com/ (accessed 1/25/2008