The Experts below are selected from a list of 1584 Experts worldwide ranked by ideXlab platform

Valerie A. Wallace - One of the best experts on this subject based on the ideXlab platform.

  • Induction of rod versus cone photoreceptor-specific progenitors from Retinal Precursor Cells.
    Stem cell research, 2018
    Co-Authors: Saeed Khalili, Brian G. Ballios, Justin Belair-hickey, Laura Donaldson, Jeff C. Liu, Brenda L.k. Coles, Kenneth Grise, Tahani Baakdhah, Gary D. Bader, Valerie A. Wallace
    Abstract:

    During development, multipotent progenitors undergo temporally-restricted differentiation into post-mitotic Retinal Cells; however, the mechanisms of progenitor division that occurs during retinogenesis remain controversial. Using clonal analyses (lineage tracing and single cell cultures), we identify rod versus cone lineage-specific progenitors derived from both adult Retinal stem Cells and embryonic neural Retinal Precursors. Taurine and retinoic acid are shown to act in an instructive and lineage-restricted manner early in the progenitor lineage hierarchy to produce rod-restricted progenitors from stem cell progeny. We also identify an instructive, but lineage-independent, mechanism for the specification of cone-restricted progenitors through the suppression of multiple differentiation signaling pathways. These data indicate that exogenous signals play critical roles in directing lineage decisions and resulting in fate-restricted rod or cone photoreceptor progenitors in culture. Additional factors may be involved in governing photoreceptor fates in vivo.

  • Retinal ganglion cell-derived sonic hedgehog locally controls proliferation and the timing of RGC development in the embryonic mouse retina
    Development (Cambridge England), 2005
    Co-Authors: Yaping Wang, Gabriel D. Dakubo, Sherry Thurig, Chantal Mazerolle, Valerie A. Wallace
    Abstract:

    The timing of cell cycle exit and temporal changes in the developmental competence of Precursor Cells are key components for the establishment of the normal complement of cell types in the mammalian retina. The identity of cell extrinsic cues that control these processes is largely unknown. We showed previously in mouse retina that sonic hedgehog (Shh) signalling from Retinal ganglion Cells (RGCs) to Retinal Precursor Cells (RPC) is required for the establishment of normal Retinal organization. Here, we show that conditional ablation of Shh expression in the peripheral mouse results in a depletion of the RPC pool, owing to precocious cell-cycle exit and neuronal differentiation. These changes were correlated with the downregulation of cyclin D1 and Hes1 gene expression. Shh inactivation also results in an increase in RGC number owing to a bias of RPC towards RGC production. In contrast to zebrafish, where Shh signalling drives cell cycle exit and RGC development, our findings indicate that in the mouse retina Shh signalling is required to maintain RPC proliferation and to control the timing of RGC development.

  • Expression of Sonic hedgehog and its putative role as a Precursor cell mitogen in the developing mouse retina
    Development (Cambridge England), 1997
    Co-Authors: Abbie M. Jensen, Valerie A. Wallace
    Abstract:

    We show that Sonic hedgehog and patched are expressed in adjacent domains in the developing mouse retina. Treatment of cultures of perinatal mouse Retinal Cells with the amino-terminal fragment of Sonic hedgehog protein results in an increase in the proportion of Cells that incorporate bromodeoxuridine, in total cell numbers, and in rod photoreceptors, amacrine Cells and Muller glial Cells, suggesting that Sonic hedgehog promotes the proliferation of Retinal Precursor Cells. These findings suggest that hedgehog and patched are part of a conserved signalling pathway in Retinal development in mammals and insects.

Seth Blackshaw - One of the best experts on this subject based on the ideXlab platform.

  • The long noncoding RNA RNCR2 directs mouse Retinal cell specification
    BMC developmental biology, 2010
    Co-Authors: Nicole A Rapicavoli, Erin M. Poth, Seth Blackshaw
    Abstract:

    Recent work has identified that many long mRNA-like noncoding RNAs (lncRNAs) are expressed in the developing nervous system. Despite their abundance, the function of these ncRNAs has remained largely unexplored. We have investigated the highly abundant lncRNA RNCR2 in regulation of mouse Retinal cell differentiation. We find that the RNCR2 is selectively expressed in a subset of both mitotic progenitors and postmitotic Retinal Precursor Cells. ShRNA-mediated knockdown of RNCR2 results in an increase of both amacrine Cells and Muller glia, indicating a role for this lncRNA in regulating Retinal cell fate specification. We further report that RNCR2 RNA, which is normally nuclear-retained, can be exported from the nucleus when fused to an IRES-GFP sequence. Overexpression of RNCR2-IRES-GFP phenocopies the effects of shRNA-mediated knockdown of RNCR2, implying that forced mislocalization of RNCR2 induces a dominant-negative phenotype. Finally, we use the IRES-GFP fusion approach to identify specific domains of RNCR2 that are required for repressing both amacrine and Muller glial differentiation. These data demonstrate that the lncRNA RNCR2 plays a critical role in regulating mammalian Retinal cell fate specification. Furthermore, we present a novel approach for generating dominant-negative constructs of lncRNAs, which may be generally useful in the functional analysis of this class of molecules.

  • The long noncoding RNA RNCR2 directs mouse Retinal cell specification
    BMC Developmental Biology, 2010
    Co-Authors: Nicole A Rapicavoli, Erin M. Poth, Seth Blackshaw
    Abstract:

    Background Recent work has identified that many long mRNA-like noncoding RNAs (lncRNAs) are expressed in the developing nervous system. Despite their abundance, the function of these ncRNAs has remained largely unexplored. We have investigated the highly abundant lncRNA RNCR2 in regulation of mouse Retinal cell differentiation. Results We find that the RNCR2 is selectively expressed in a subset of both mitotic progenitors and postmitotic Retinal Precursor Cells. ShRNA-mediated knockdown of RNCR2 results in an increase of both amacrine Cells and Müller glia, indicating a role for this lncRNA in regulating Retinal cell fate specification. We further report that RNCR2 RNA, which is normally nuclear-retained, can be exported from the nucleus when fused to an IRES-GFP sequence. Overexpression of RNCR2-IRES-GFP phenocopies the effects of shRNA-mediated knockdown of RNCR2, implying that forced mislocalization of RNCR2 induces a dominant-negative phenotype. Finally, we use the IRES-GFP fusion approach to identify specific domains of RNCR2 that are required for repressing both amacrine and Müller glial differentiation. Conclusion These data demonstrate that the lncRNA RNCR2 plays a critical role in regulating mammalian Retinal cell fate specification. Furthermore, we present a novel approach for generating dominant-negative constructs of lncRNAs, which may be generally useful in the functional analysis of this class of molecules.

Nicole A Rapicavoli - One of the best experts on this subject based on the ideXlab platform.

  • The long noncoding RNA RNCR2 directs mouse Retinal cell specification
    BMC developmental biology, 2010
    Co-Authors: Nicole A Rapicavoli, Erin M. Poth, Seth Blackshaw
    Abstract:

    Recent work has identified that many long mRNA-like noncoding RNAs (lncRNAs) are expressed in the developing nervous system. Despite their abundance, the function of these ncRNAs has remained largely unexplored. We have investigated the highly abundant lncRNA RNCR2 in regulation of mouse Retinal cell differentiation. We find that the RNCR2 is selectively expressed in a subset of both mitotic progenitors and postmitotic Retinal Precursor Cells. ShRNA-mediated knockdown of RNCR2 results in an increase of both amacrine Cells and Muller glia, indicating a role for this lncRNA in regulating Retinal cell fate specification. We further report that RNCR2 RNA, which is normally nuclear-retained, can be exported from the nucleus when fused to an IRES-GFP sequence. Overexpression of RNCR2-IRES-GFP phenocopies the effects of shRNA-mediated knockdown of RNCR2, implying that forced mislocalization of RNCR2 induces a dominant-negative phenotype. Finally, we use the IRES-GFP fusion approach to identify specific domains of RNCR2 that are required for repressing both amacrine and Muller glial differentiation. These data demonstrate that the lncRNA RNCR2 plays a critical role in regulating mammalian Retinal cell fate specification. Furthermore, we present a novel approach for generating dominant-negative constructs of lncRNAs, which may be generally useful in the functional analysis of this class of molecules.

  • The long noncoding RNA RNCR2 directs mouse Retinal cell specification
    BMC Developmental Biology, 2010
    Co-Authors: Nicole A Rapicavoli, Erin M. Poth, Seth Blackshaw
    Abstract:

    Background Recent work has identified that many long mRNA-like noncoding RNAs (lncRNAs) are expressed in the developing nervous system. Despite their abundance, the function of these ncRNAs has remained largely unexplored. We have investigated the highly abundant lncRNA RNCR2 in regulation of mouse Retinal cell differentiation. Results We find that the RNCR2 is selectively expressed in a subset of both mitotic progenitors and postmitotic Retinal Precursor Cells. ShRNA-mediated knockdown of RNCR2 results in an increase of both amacrine Cells and Müller glia, indicating a role for this lncRNA in regulating Retinal cell fate specification. We further report that RNCR2 RNA, which is normally nuclear-retained, can be exported from the nucleus when fused to an IRES-GFP sequence. Overexpression of RNCR2-IRES-GFP phenocopies the effects of shRNA-mediated knockdown of RNCR2, implying that forced mislocalization of RNCR2 induces a dominant-negative phenotype. Finally, we use the IRES-GFP fusion approach to identify specific domains of RNCR2 that are required for repressing both amacrine and Müller glial differentiation. Conclusion These data demonstrate that the lncRNA RNCR2 plays a critical role in regulating mammalian Retinal cell fate specification. Furthermore, we present a novel approach for generating dominant-negative constructs of lncRNAs, which may be generally useful in the functional analysis of this class of molecules.

Pierre Voisin - One of the best experts on this subject based on the ideXlab platform.

  • Cyclic AMP-dependent regulation of tyrosine hydroxylase mRNA and immunofluorescence levels in rat Retinal Precursor Cells
    Cell and Tissue Research, 2013
    Co-Authors: Pierre Voisin, Marianne Bernard
    Abstract:

    Stimulation of tyrosine hydroxylase (TH) gene transcription by cyclic AMP (cAMP) has been clearly established in adrenal medula Cells and neural-crest-derived cell lines but information on this mechanism is still lacking in dopaminergic neurons. Because they are easily amenable to in vitro experiments, dopaminergic amacrine Cells of the retina might constitute a valuable model system to study this mechanism. We have used real-time reverse transcription with the polymerase chain reaction to quantify TH mRNA levels in the rat retina during post-natal development and in Retinal Precursor Cells obtained from neonatal rats and cultured for 3 days in serum-free medium. Whereas the TH mRNA concentration remains consistantly low in control cultures, treatment with cAMP-increasing agents (forskolin, membrane depolarization, phosphodiesterase inhibitors) is sufficient to raise it to the level observed in adult retina (15-fold increase). Treatment of the cultured Cells can be delayed by up to 2 days with identical results at the TH mRNA level, thus ruling out a survival-promoting effect of cAMP. TH immunofluorescence has confirmed cAMP-dependent regulation of TH expression at the protein level and indicates that the frequency of TH-positive Cells in the cultures is similar to that observed in the adult retina. Selective phosphodiesterase inhibitors suggest that PDE4 is the major subtype involved in the dopaminergic amacrine cell response. Our data clearly establish the cAMP-dependent regulation of TH mRNA and immunofluorescence levels in Retinal Precursor Cells. The possible role of this regulation mechanism in the developmental activation of TH gene expression is discussed.

  • Visual photoreceptor subtypes in the chicken retina: melatonin-synthesizing activity and in vitro differentiation
    Cell and Tissue Research, 2012
    Co-Authors: Pierre Voisin, Virginie Cailleau, N. Naud, A. Cantereau, M. Bernard
    Abstract:

    The chicken retina contains five visual photoreceptor subtypes, based on the specific opsin gene they express. In addition to the central role they play in vision, some or all of these photoreceptors translate photoperiodic information into a day–night rhythm of melatonin production. This indolic hormone plays an important role in the photoperiodic regulation of Retinal physiology. Previous studies have stopped short of establishing whether melatonin synthesis takes place in all the photoreceptor spectral subtypes. Another issue that has been left unsettled by previous studies is when during development are Retinal Precursor Cells committed to a specific photoreceptor subtype and to a melatoninergic phenotype? To address the first question, in situ hybridization of the five opsins was combined with immunofluorescent detection of the melatonin-synthesizing enzyme hydroxyindole O-methyltransferase (HIOMT, EC.2.1.1.4). Confocal microscopy clearly indicated that all photoreceptor spectral subtypes are involved in melatonin synthesis. To tackle the second question, Retinal Precursor Cells were dissociated between embryonic day 6 (E6) and E13 and cultured in serum-free medium for 4 days to examine their ability to autonomously activate the expression of opsins and HIOMT. Real-time PCR on cultured Precursors indicated that red-, green- and violet-sensitive cones are committed at E6, rods at E10 and blue-sensitive cones at E12. HIOMT gene expression was programmed at E6, probably reflecting the differentiation of early cones. The present study provides a better characterization of photoreceptor subtypes in the chicken retina and describes a combination of serum-free culture and real-time PCR that should facilitate further developmental studies.

  • Cyclic AMP‐dependent activation of rhodopsin gene transcription in cultured Retinal Precursor Cells of chicken embryo
    Journal of neurochemistry, 2009
    Co-Authors: Pierre Voisin, Marianne Bernard
    Abstract:

    The present study describes a robust 50-fold increase in rhodopsin gene transcription by cAMP in cultured Retinal Precursor Cells of chicken embryo. Retinal Cells isolated at embryonic day 8 (E8) and cultured for 3 days in serum-supplemented medium differentiated mostly into red-sensitive cones and to a lesser degree into green-sensitive cones, as indicated by real-time RT-PCR quantification of each specific opsin mRNA. In contrast, both rhodopsin mRNA concentration and rhodopsin gene promoter activity required the presence of cAMP-increasing agents [forskolin and 3-isobutyl-1-methylxanthine (IBMX)] to reach significant levels. This response was rod-specific and was sufficient to activate rhodopsin gene transcription in serum-free medium. The increase in rhodopsin mRNA levels evoked by a series of cAMP analogs suggested the response was mediated by protein kinase A, not by EPAC. Membrane depolarization by high KCl concentration also increased rhodopsin mRNA levels and this response was strongly potentiated by IBMX. The rhodopsin gene response to cAMP-increasing agents was developmentally gated between E6 and E7. Rod-specific transducin alpha subunit mRNA levels also increased up to 50-fold in response to forskolin and IBMX, while rod-specific phosphodiesterase-VI and rod arrestin transcripts increased 3- to 10-fold. These results suggest a cAMP-mediated signaling pathway may play a role in rod differentiation.

  • Cyclic AMP-dependent activation of rhodopsin gene transcription in cultured Retinal Precursor Cells of chicken embryo.
    Journal of Neurochemistry, 2009
    Co-Authors: Pierre Voisin, Marianne Bernard
    Abstract:

    The present study describes a robust 50-fold increase in rhodopsin gene transcription by cAMP in cultured Retinal Precursor Cells of chicken embryo. Retinal Cells isolated at embryonic day 8 (E8) and cultured for 3 days in serum-supplemented medium differentiated mostly into red-sensitive cones and to a lesser degree into green-sensitive cones, as indicated by real-time RT-PCR quantification of each specific opsin mRNA. In contrast, both rhodopsin mRNA concentration and rhodopsin gene promoter activity required the presence of cAMP-increasing agents [forskolin and 3-isobutyl-1-methylxanthine (IBMX)] to reach significant levels. This response was rod-specific and was sufficient to activate rhodopsin gene transcription in serum-free medium. The increase in rhodopsin mRNA levels evoked by a series of cAMP analogs suggested the response was mediated by protein kinase A, not by EPAC. Membrane depolarization by high KCl concentration also increased rhodopsin mRNA levels and this response was strongly potentiated by IBMX. The rhodopsin gene response to cAMP-increasing agents was developmentally gated between E6 and E7. Rod-specific transducin alpha subunit mRNA levels also increased up to 50-fold in response to forskolin and IBMX, while rod-specific phosphodiesterase-VI and rod arrestin transcripts increased 3- to 10-fold. These results suggest a cAMP-mediated signaling pathway may play a role in rod differentiation.

  • Differential regulation of melatonin synthesis genes and phototransduction genes in embryonic chicken retina and cultured Retinal Precursor Cells.
    Molecular Vision, 2005
    Co-Authors: Virginie Cailleau, Marianne Bernard, Fabrice Morin, Jérôme Guerlotté, Pierre Voisin
    Abstract:

    Photoreceptor differentiation involves the activation of two specific sets of genes; those encoding the proteins of the phototransduction cascade and those encoding the enzymes of the melatonin synthesis pathway, arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole O-methyltransferase (HIOMT). The purpose of the present study was to examine the conditions of AANAT and HIOMT gene activation, relative to that of selected phototransduction markers (alpha-transducin and opsins), in both in vivo and in vitro differentiating photoreceptors of the chicken retina.

Mogens Holst Nissen - One of the best experts on this subject based on the ideXlab platform.

  • Vitreous humor and albumin augment the proliferation of cultured Retinal Precursor Cells.
    Journal of neuroscience research, 2009
    Co-Authors: Jing Yang, Henry Klassen, Mette Pries, Wei Wang, Mogens Holst Nissen
    Abstract:

    Intravitreal injection is an important delivery route for studies involving the transplantation of various types of Precursor Cells to the retina; however, the effect on these Cells of exposure to the vitreous microenvironment has not been specifically investigated. Here vitreous humor was evaluated for the potential to influence the proliferation of rat Retinal Precursor Cells in vitro. Cells were isolated at embryonic day 19 and plated in standard proliferation medium in the presence or absence of fluid expressed from porcine vitreous humor. Cellular proliferation at different concentrations of vitreous fluid supplementation was quantified by using a (3)H-thymidine incorporation assay. Active components of vitreous fluid were partially characterized by gel filtration chromatography (GFC) and UV spectral analysis. The effect of each vitreous fraction on proliferation was determined as well. Results showed that addition of 20% vitreous fluid to primary rat Retinal cultures significantly increased (3)H-thymidine incorporation compared with growth medium without vitreous supplementation. A vitreous fraction showing growth-promoting activity was localized to a molecular mass range

  • vitreous humor and albumin augment the proliferation of cultured Retinal Precursor Cells
    Journal of Neuroscience Research, 2009
    Co-Authors: Jing Yang, Henry Klassen, Mette Pries, Wei Wang, Mogens Holst Nissen
    Abstract:

    Intravitreal injection is an important delivery route for studies involving the transplantation of various types of Precursor Cells to the retina; however, the effect on these Cells of exposure to the vitreous microenvironment has not been specifically investigated. Here vitreous humor was evaluated for the potential to influence the proliferation of rat Retinal Precursor Cells in vitro. Cells were isolated at embryonic day 19 and plated in standard proliferation medium in the presence or absence of fluid expressed from porcine vitreous humor. Cellular proliferation at different concentrations of vitreous fluid supplementation was quantified by using a (3)H-thymidine incorporation assay. Active components of vitreous fluid were partially characterized by gel filtration chromatography (GFC) and UV spectral analysis. The effect of each vitreous fraction on proliferation was determined as well. Results showed that addition of 20% vitreous fluid to primary rat Retinal cultures significantly increased (3)H-thymidine incorporation compared with growth medium without vitreous supplementation. A vitreous fraction showing growth-promoting activity was localized to a molecular mass range <1000 Da, consistent with ascorbic acid. Ascorbic acid was confirmed in vitreous fluid by UV spectral analysis. Growth-augmenting activity was present in higher molecular mass vitreous fractions, consistent with protein components. Albumin, the major protein in vitreous fluid, was found to augment proliferation. Because vitreous-associated augmentation of Retinal Precursor proliferation remains an epidermal growth factor-dependent phenomenon, the proliferative status of transplanted Cells in the vitreous cavity is likely determined by a combination of factors.

  • Aqueous humor enhances the proliferation of rat Retinal Precursor Cells in culture, and this effect is partially reproduced by ascorbic acid.
    Stem cells (Dayton Ohio), 2006
    Co-Authors: Jing Yang, Henry Klassen, Mette Pries, Wei Wang, Mogens Holst Nissen
    Abstract:

    Aqueous humor has been shown to influence the proliferation of various ocular cell types, but the effect on immature Retinal Cells is not known. Here, the effect of pig aqueous humor on the proliferation of rat Retinal Precursor Cells (RPCs) was investigated. RPCs were prepared from embryonic day 19 Sprague-Dawley rats and cultured in the presence or absence of aqueous humor from healthy pigs along with a medium consisting of Dulbecco's modified Eagle's medium:Ham's F-12 medium, N2 supplement, and epidermal growth factor. Proliferation was quantified by [(3)H]thymidine incorporation under different treatment conditions, and any associated morphological changes were noted. Potential active components of porcine aqueous humor were partially characterized by gel filtration chromatography, and the effect on RPC proliferation was determined. Results showed that adding 20% aqueous humor increased [(3)H]thymidine incorporation by as much as 317%, as compared with controls. Aqueous supplementation also increased both the number and size of RPC spherical aggregates ("spheres") over the first 4 days, consistent with increased proliferative activity. Using gel filtration and the in vitro proliferation assay, the growth-promoting activity of aqueous humor was localized to two different molecular mass ranges, namely, around 30 kDa and less than 1 kDa. Ascorbic acid was present in the lower molecular mass fraction, and use of this molecule reproduced some, but not all, of the proliferative activity present in aqueous humor. These results highlight the potential role of soluble factors present in the cellular microenvironment with respect to modulation of endogenous progenitor cell activity.