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Kulesh B, Bozadjian R, Parisi RJ, Leong SA, Kautzman AG, Reese BE, Keeley PW. Quantitative trait loci on chromosomes 9 and 19 modulate AII amacrine cell number in the mouse retina. Front Neurosci 2023; 17:1078168. [PMID: 36816119 PMCID: PMC9932814 DOI: 10.3389/fnins.2023.1078168] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/03/2023] [Indexed: 02/05/2023] Open
Abstract
Sequence variants modulating gene function or expression affect various heritable traits, including the number of neurons within a population. The present study employed a forward-genetic approach to identify candidate causal genes and their sequence variants controlling the number of one type of retinal neuron, the AII amacrine cell. Data from twenty-six recombinant inbred (RI) strains of mice derived from the parental C57BL/6J (B6/J) and A/J laboratory strains were used to identify genomic loci regulating cell number. Large variation in cell number is present across the RI strains, from a low of ∼57,000 cells to a high of ∼87,000 cells. Quantitative trait locus (QTL) analysis revealed three prospective controlling genomic loci, on Chromosomes (Chrs) 9, 11, and 19, each contributing additive effects that together approach the range of variation observed. Composite interval mapping validated two of these loci, and chromosome substitution strains, in which the A/J genome for Chr 9 or 19 was introgressed on a B6/J genetic background, showed increased numbers of AII amacrine cells as predicted by those two QTL effects. Analysis of the respective genomic loci identified candidate controlling genes defined by their retinal expression, their established biological functions, and by the presence of sequence variants expected to modulate gene function or expression. Two candidate genes, Dtx4 on Chr 19, being a regulator of Notch signaling, and Dixdc1 on Chr 9, a modulator of the WNT-β-catenin signaling pathway, were explored in further detail. Postnatal overexpression of Dtx4 was found to reduce the frequency of amacrine cells, while Dixdc1 knockout retinas contained an excess of AII amacrine cells. Sequence variants in each gene were identified, being the likely sources of variation in gene expression, ultimately contributing to the final number of AII amacrine cells.
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Affiliation(s)
- Bridget Kulesh
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Rachel Bozadjian
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Ryan J. Parisi
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Stephanie A. Leong
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Amanda G. Kautzman
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Benjamin E. Reese
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Patrick W. Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
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Keeley PW, Patel PS, Ryu MS, Reese BE. Neurog2 regulates Isl1 to modulate horizontal cell number. Development 2023; 150:dev201315. [PMID: 36537573 PMCID: PMC10108602 DOI: 10.1242/dev.201315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 12/06/2022] [Indexed: 12/24/2022]
Abstract
The population sizes of different retinal cell types vary between different strains of mice, and that variation can be mapped to genomic loci in order to identify its polygenic origin. In some cases, controlling genes act independently, whereas in other instances, they exhibit epistasis. Here, we identify an epistatic interaction revealed through the mapping of quantitative trait loci from a panel of recombinant inbred strains of mice. The population of retinal horizontal cells exhibits a twofold variation in number, mapping to quantitative trait loci on chromosomes 3 and 13, where these loci are shown to interact epistatically. We identify a prospective genetic interaction underlying this, mediated by the bHLH transcription factor Neurog2, at the chromosome 3 locus, functioning to repress the LIM homeodomain transcription factor Isl1, at the chromosome 13 locus. Using single and double conditional knockout mice, we confirm the countervailing actions of each gene, and validate in vitro a crucial role for two single nucleotide polymorphisms in the 5'UTR of Isl1, one of which yields a novel E-box, mediating the repressive action of Neurog2.
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Affiliation(s)
- Patrick W. Keeley
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
| | - Pooja S. Patel
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
| | - Matthew S. Ryu
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
| | - Benjamin E. Reese
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
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3
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Interrelationships between Cellular Density, Mosaic Patterning, and Dendritic Coverage of VGluT3 Amacrine Cells. J Neurosci 2021; 41:103-117. [PMID: 33208470 DOI: 10.1523/jneurosci.1027-20.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 11/02/2020] [Accepted: 11/05/2020] [Indexed: 01/15/2023] Open
Abstract
Amacrine cells of the retina are conspicuously variable in their morphologies, their population demographics, and their ensuing functions. Vesicular glutamate transporter 3 (VGluT3) amacrine cells are a recently characterized type of amacrine cell exhibiting local dendritic autonomy. The present analysis has examined three features of this VGluT3 population, including their density, local distribution, and dendritic spread, to discern the extent to which these are interrelated, using male and female mice. We first demonstrate that Bax-mediated cell death transforms the mosaic of VGluT3 cells from a random distribution into a regular mosaic. We subsequently examine the relationship between cell density and mosaic regularity across recombinant inbred strains of mice, finding that, although both traits vary across the strains, they exhibit minimal covariation. Other genetic determinants must therefore contribute independently to final cell number and to mosaic order. Using a conditional KO approach, we further demonstrate that Bax acts via the bipolar cell population, rather than cell-intrinsically, to control VGluT3 cell number. Finally, we consider the relationship between the dendritic arbors of single VGluT3 cells and the distribution of their homotypic neighbors. Dendritic field area was found to be independent of Voronoi domain area, while dendritic coverage of single cells was not conserved, simply increasing with the size of the dendritic field. Bax-KO retinas exhibited a threefold increase in dendritic coverage. Each cell, however, contributed less dendrites at each depth within the plexus, intermingling their processes with those of neighboring cells to approximate a constant volumetric density, yielding a uniformity in process coverage across the population.SIGNIFICANCE STATEMENT Different types of retinal neuron spread their processes across the surface of the retina to achieve a degree of dendritic coverage that is characteristic of each type. Many of these types achieve a constant coverage by varying their dendritic field area inversely with the local density of like-type neighbors. Here we report a population of retinal amacrine cells that do not develop dendritic arbors in relation to the spatial positioning of such homotypic neighbors; rather, this cell type modulates the extent of its dendritic branching when faced with a variable number of overlapping dendritic fields to approximate a uniformity in dendritic density across the retina.
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Jiang D, Burger CA, Casasent A, Albrecht NE, Li F, Samuel MA. Spatiotemporal gene expression patterns reveal molecular relatedness between retinal laminae. J Comp Neurol 2020; 528:729-755. [PMID: 31609468 PMCID: PMC7147688 DOI: 10.1002/cne.24784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 08/28/2019] [Accepted: 09/13/2019] [Indexed: 12/16/2022]
Abstract
In several areas of the central nervous system, neurons are regionally organized into groups or layers that carry out specific activities. In this form of patterning, neurons of distinct types localize their cell bodies to just one or a few of the layers within a structure. However, little is known about whether diverse neuron types within a lamina share molecular features that coordinate their organization. To begin to identify such candidates, we used the laminated murine retina to screen 92 lacZ reporter lines available through the Knockout Mouse Project. Thirty-two of these displayed reporter expression in restricted subsets of inner retina neurons. We then identified the spatiotemporal expression patterns of these genes at key developmental stages. This uncovered several that were heavily enriched in development but reduced in adulthood, including the transcriptional regulator Hmga1. An additional set of genes displayed maturation associated laminar enrichment. Among these, we identified Bbox1 as a novel gene that specifically labels all neurons in the ganglion cell layer but is largely excluded from otherwise molecularly similar neurons in the inner retina. Finally, we established Dbn1 as a new marker enriched in amacrines and Fmnl3 as a marker for subsets of αRGCs. Together, these data provide a spatiotemporal map for laminae-specific molecules and suggest that diverse neuron types within a lamina share coordinating molecular features that may inform their fate or function.
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Affiliation(s)
- Danye Jiang
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
| | - Courtney A. Burger
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
| | - Anna Casasent
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
| | - Nicholas E. Albrecht
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
| | - Fenge Li
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
| | - Melanie A. Samuel
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
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5
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Geisert EE, Williams RW. Using BXD mouse strains in vision research: A systems genetics approach. Mol Vis 2020; 26:173-187. [PMID: 32180682 PMCID: PMC7058434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 03/04/2020] [Indexed: 11/06/2022] Open
Abstract
We illustrate the growing power of the BXD family of mice (recombinant inbred strains from a cross of C57BL/6J and DBA/2J mice) and companion bioinformatic tools to study complex genome-phenome relations related to glaucoma. Over the past 16 years, our group has integrated powerful murine resources and web-accessible tools to identify networks modulating visual system traits-from photoreceptors to the visual cortex. Recent studies focused on retinal ganglion cells and glaucoma risk factors, including intraocular pressure (IOP), central corneal thickness (CCT), and susceptibility of cellular stress. The BXD family was exploited to define key gene variants and then establish linkage to glaucoma in human cohorts. The power of this experimental approach to precision medicine is highlighted by recent studies that defined cadherin 11 (Cdh11) and a calcium channel (Cacna2d1) as genes modulating IOP, Pou6f2 as a genetic link between CCT and retinal ganglion cell (RGC) death, and Aldh7a1 as a gene that modulates the susceptibility of RGCs to death after elevated IOP. The role of three of these gene variants in glaucoma is discussed, along with the pathways activated in the disease process.
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Affiliation(s)
- Eldon E. Geisert
- Department of Ophthalmology, Emory University, 1365B Clifton Road NE Atlanta GA, 30322
| | - Robert W. Williams
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, 71 S Manassas St, Memphis TN 38163
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Stefanov A, Novelli E, Strettoi E. Inner retinal preservation in the photoinducible I307N rhodopsin mutant mouse, a model of autosomal dominant retinitis pigmentosa. J Comp Neurol 2019; 528:1502-1522. [PMID: 31811649 PMCID: PMC7187456 DOI: 10.1002/cne.24838] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 12/03/2019] [Accepted: 12/03/2019] [Indexed: 12/20/2022]
Abstract
Rod‐cone degenerations, for example, retinitis pigmentosa are leading causes of blindness worldwide. Despite slow disease progression in humans, vision loss is inevitable; therefore, development of vision restoration strategies is crucial. Among others, promising approaches include optogenetics and prosthetic implants, which aim to bypass lost photoreceptors (PRs). Naturally, the efficacy of these therapeutic strategies will depend on inner retinal structural and functional preservation. The present study shows that in photoinducible I307N rhodopsin mice (Translational Vision Research Model 4 [Tvrm4]), a 12k lux light exposure eliminates PRs in the central retina in 1 week, but interneurons and their synapses are maintained for as long as 9 weeks postinduction. Despite bipolar cell dendritic retraction and moderate loss of horizontal cells, the survival rate of various cell types is very high. Significant preservation of conventional synapses and gap junctions in the inner plexiform layer is also observed. We found the number of synaptic ribbons to gradually decline and their ultrastructure to become transiently abnormal, although based on our findings intrinsic retinal architecture is maintained despite complete loss of PRs. Unlike common rodent models of PR degeneration, where the disease phenotype often interferes with retinal development, in Tvrm4 mice, the degenerative process can be induced after retinal development is complete. This time course more closely mimics the timing of disease onset in affected patients. Stability of the inner retina found in these mutants 2 months after PR degeneration suggests moderate, stereotyped remodeling in the early stages of the human disease and represents a promising finding for prompt approaches of vision restoration.
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Affiliation(s)
- Antonia Stefanov
- Institute of Neuroscience, Italian National Research Council - CNR, Pisa, Italy.,Regional Doctoral School of Neuroscience, University of Florence, Florence, Italy
| | - Elena Novelli
- Institute of Neuroscience, Italian National Research Council - CNR, Pisa, Italy
| | - Enrica Strettoi
- Institute of Neuroscience, Italian National Research Council - CNR, Pisa, Italy
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7
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Kautzman AG, Keeley PW, Ackley CR, Leong S, Whitney IE, Reese BE. Xkr8 Modulates Bipolar Cell Number in the Mouse Retina. Front Neurosci 2018; 12:876. [PMID: 30559640 PMCID: PMC6286994 DOI: 10.3389/fnins.2018.00876] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 11/09/2018] [Indexed: 12/25/2022] Open
Abstract
The present study interrogated a quantitative trait locus (QTL) on Chr 4 associated with the population sizes of two types of bipolar cell in the mouse retina. This locus was identified by quantifying the number of rod bipolar cells and Type 2 cone bipolar cells across a panel of recombinant inbred (RI) strains of mice derived from two inbred laboratory strains, C57BL/6J (B6/J) and A/J, and mapping a proportion of that variation in cell number, for each cell type, to this shared locus. There, we identified the candidate gene X Kell blood group precursor related family member 8 homolog (Xkr8). While Xkr8 has no documented role in the retina, we localize robust expression in the mature retina via in situ hybridization, confirm its developmental presence via immunolabeling, and show that it is differentially regulated during the postnatal period between the B6/J and A/J strains using qPCR. Microarray analysis, derived from whole eye mRNA from the entire RI strain set, demonstrates significant negative correlation of Xkr8 expression with the number of each of these two types of bipolar cells, and the variation in Xkr8 expression across the strains maps a cis-eQTL, implicating a regulatory variant discriminating the parental genomes. Xkr8 plasmid electroporation during development yielded a reduction in the number of bipolar cells in the retina, while sequence analysis of Xkr8 in the two parental strain genomes identified a structural variant in the 3′ UTR that may disrupt mRNA stability, and two SNPs in the promoter that create transcription factor binding sites. We propose that Xkr8, via its participation in mediating cell death, plays a role in the specification of bipolar cell number in the retina.
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Affiliation(s)
- Amanda G Kautzman
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Patrick W Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Caroline R Ackley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Stephanie Leong
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Irene E Whitney
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
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8
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Munteanu T, Noronha KJ, Leung AC, Pan S, Lucas JA, Schmidt TM. Light-dependent pathways for dopaminergic amacrine cell development and function. eLife 2018; 7:39866. [PMID: 30403373 PMCID: PMC6221543 DOI: 10.7554/elife.39866] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 10/26/2018] [Indexed: 11/13/2022] Open
Abstract
Retinal dopamine is a critical modulator of high acuity, light-adapted vision and photoreceptor coupling in the retina. Dopaminergic amacrine cells (DACs) serve as the sole source of retinal dopamine, and dopamine release in the retina follows a circadian rhythm and is modulated by light exposure. However, the retinal circuits through which light influences the development and function of DACs are still unknown. Intrinsically photosensitive retinal ganglion cells (ipRGCs) have emerged as a prime target for influencing retinal dopamine levels because they costratify with DACs in the inner plexiform layer and signal to them in a retrograde manner. Surprisingly, using genetic mouse models lacking specific phototransduction pathways, we find that while light influences the total number of DACs and retinal dopamine levels, this effect does not require ipRGCs. Instead, we find that the rod pathway is a critical modulator of both DAC number and retinal dopamine levels.
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Affiliation(s)
- Teona Munteanu
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Katelyn J Noronha
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Amanda C Leung
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Simon Pan
- Department of Biology, Johns Hopkins University, Baltimore, United States
| | - Jasmine A Lucas
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Tiffany M Schmidt
- Department of Neurobiology, Northwestern University, Evanston, United States
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9
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Sankaran M, Keeley PW, He L, Iuvone PM, Reese BE. Dopaminergic amacrine cell number, plexus density, and dopamine content in the mouse retina: Strain differences and effects of Bax gene disruption. Exp Eye Res 2018; 177:208-212. [PMID: 30240584 DOI: 10.1016/j.exer.2018.09.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 08/07/2018] [Accepted: 09/17/2018] [Indexed: 01/01/2023]
Abstract
Many types of retinal neuron modulate the distribution of their processes to ensure a uniform coverage of the retinal surface. Dendritic field area, for instance, is inversely related to the variation in cellular density for many cell types, observed either across retinal eccentricity or between different strains of mice that differ in cell number. Dopaminergic amacrine (DA) cells, by contrast, have dendritic arbors that bear no spatial relationship to the presence of their immediate homotypic neighbors, yet it remains to be determined whether their coverage upon the retina, as a population, is conserved across variation in their total number. The present study assessed the overall density of the dopaminergic plexus in the inner plexiform layer in the presence of large variation in the total number of DA cells, as well as their retinal dopamine content, to determine whether either of these features is conserved. We first compared these traits between two strains of mice (C57BL/6J and A/J) that exhibit a two-fold difference in DA cell number. We subsequently examined these same traits in littermate mice for which the pro-apoptotic Bax gene was either intact or knocked out, yielding a five-fold difference in DA cell number. In both comparisons, we found greater plexus density and DA content in the strain or condition with the greater number of DA cells. The population of DA cells, therefore, does not appear to self-regulate its process coverage to achieve a constant density as the DA mosaic is established during development, nor its functional dopamine content in maturity.
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Affiliation(s)
- Mathangi Sankaran
- Neuroscience Research Institute, University of California, Santa Barbara, CA, 93106, USA; Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA, 93106, USA
| | - Patrick W Keeley
- Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA, 93106, USA
| | - Li He
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - P Michael Iuvone
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, 30322, USA; Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, CA, 93106, USA; Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA, 93106, USA.
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10
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Kautzman AG, Keeley PW, Borhanian S, Ackley CR, Reese BE. Genetic Control of Rod Bipolar Cell Number in the Mouse Retina. Front Neurosci 2018; 12:285. [PMID: 29867309 PMCID: PMC5954209 DOI: 10.3389/fnins.2018.00285] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/11/2018] [Indexed: 12/31/2022] Open
Abstract
Genetic variants modulate the numbers of various retinal cell types in mice. For instance, there is minimal variation in the number of rod bipolar cells (RBCs) in two inbred strains of mice (A/J and C57BL/6J), yet their F1 offspring contain significantly more RBCs than either parental strain. To investigate the genetic source of this variation, we mapped the variation in the number of RBCs across 24 genetically distinct recombinant inbred (RI) strains (the AXB/BXA strain-set), seeking to identify quantitative trait loci (QTL). We then sought to identify candidate genes and potential casual variants at those genomic loci. Variation in RBC number mapped to three genomic loci, each modulating cell number in excess of one-third of the range observed across the RI strains. At each of these loci, we identified candidate genes containing variants that might alter gene function or expression. The latter genes were also analyzed using a transcriptome database, revealing a subset for which expression correlated with variation in RBC number. Using an electroporation strategy, we demonstrate that early postnatal expression of one of them, Ggct (gamma-glutamyl cyclotransferase), modulates bipolar cell number. We identify candidate regulatory variants for this gene, finding a large structural variant (SV) in the putative promoter that reduces expression using a luciferase assay. This SV reducing Ggct expression in vitro is likely the causal variant within the gene associated with the variation in Ggct expression in vivo, implicating it as a quantitative trait variant (QTV) participating in the control of RBC number.
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Affiliation(s)
- Amanda G Kautzman
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Patrick W Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Sarra Borhanian
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Caroline R Ackley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States.,Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
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11
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Pérez de Sevilla Müller L, Solomon A, Sheets K, Hapukino H, Rodriguez AR, Brecha NC. Multiple cell types form the VIP amacrine cell population. J Comp Neurol 2017; 527:133-158. [PMID: 28472856 DOI: 10.1002/cne.24234] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 04/21/2017] [Accepted: 04/27/2017] [Indexed: 12/21/2022]
Abstract
Amacrine cells are a heterogeneous group of interneurons that form microcircuits with bipolar, amacrine and ganglion cells to process visual information in the inner retina. This study has characterized the morphology, neurochemistry and major cell types of a VIP-ires-Cre amacrine cell population. VIP-tdTomato and -Confetti (Brainbow2.1) mouse lines were generated by crossing a VIP-ires-Cre line with either a Cre-dependent tdTomato or Brainbow2.1 reporter line. Retinal sections and whole-mounts were evaluated by quantitative, immunohistochemical, and intracellular labeling approaches. The majority of tdTomato and Confetti fluorescent cell bodies were in the inner nuclear layer (INL) and a few cell bodies were in the ganglion cell layer (GCL). Fluorescent processes ramified in strata 1, 3, 4, and 5 of the inner plexiform layer (IPL). All tdTomato fluorescent cells expressed syntaxin 1A and GABA-immunoreactivity indicating they were amacrine cells. The average VIP-tdTomato fluorescent cell density in the INL and GCL was 535 and 24 cells/mm2 , respectively. TdTomato fluorescent cells in the INL and GCL contained VIP-immunoreactivity. The VIP-ires-Cre amacrine cell types were identified in VIP-Brainbow2.1 retinas or by intracellular labeling in VIP-tdTomato retinas. VIP-1 amacrine cells are bistratified, wide-field cells that ramify in strata 1, 4, and 5, VIP-2A and 2B amacrine cells are medium-field cells that mainly ramify in strata 3 and 4, and VIP-3 displaced amacrine cells are medium-field cells that ramify in strata 4 and 5 of the IPL. VIP-ires-Cre amacrine cells form a neuropeptide-expressing cell population with multiple cell types, which are likely to have distinct roles in visual processing.
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Affiliation(s)
- Luis Pérez de Sevilla Müller
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763
| | - Alexander Solomon
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763
| | - Kristopher Sheets
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763
| | - Hinekura Hapukino
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763
| | - Allen R Rodriguez
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763
| | - Nicholas C Brecha
- Department of Neurobiology, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763.,Department of Medicine, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763.,Department of Ophthalmology and the Stein Eye Institute, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763.,CURE Digestive Diseases Research Center, David Geffen School of Medicine at Los Angeles, University of California at Los Angeles, Los Angeles, California, 90095-1763.,Veterans Administration Greater Los Angeles Health System, Los Angeles, California, 90073
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Pérez de Sevilla Müller L, Azar SS, de Los Santos J, Brecha NC. Prox1 Is a Marker for AII Amacrine Cells in the Mouse Retina. Front Neuroanat 2017; 11:39. [PMID: 28529477 PMCID: PMC5418924 DOI: 10.3389/fnana.2017.00039] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 04/18/2017] [Indexed: 12/18/2022] Open
Abstract
The transcription factor Prox1 is expressed in multiple cells in the retina during eye development. This study has focused on neuronal Prox1 expression in the inner nuclear layer (INL) of the adult mouse retina. Prox1 immunostaining was evaluated in vertical retinal sections and whole mount preparations using a specific antibody directed to the C-terminus of Prox1. Strong immunostaining was observed in numerous amacrine cell bodies and in all horizontal cell bodies in the proximal and distal INL, respectively. Some bipolar cells were also weakly immunostained. Prox1-immunoreactive amacrine cells expressed glycine, and they formed 35 ± 3% of all glycinergic amacrine cells. Intracellular Neurobiotin injections into AII amacrine cells showed that all gap junction-coupled AII amacrine cells express Prox1, and no other Prox1-immunostained amacrine cells were in the immediate area surrounding the injected AII amacrine cell. Prox1-immunoreactive amacrine cell bodies were distributed across the retina, with their highest density (3887 ± 160 cells/mm2) in the central retina, 0.5 mm from the optic nerve head, and their lowest density (3133 ± 350 cells/mm2) in the mid-peripheral retina, 2 mm from the optic nerve head. Prox1-immunoreactive amacrine cell bodies comprised ~9.8% of the total amacrine cell population, and they formed a non-random mosaic with a regularity index (RI) of 3.4, similar to AII amacrine cells in the retinas of other mammals. Together, these findings indicate that AII amacrine cells are the predominant and likely only amacrine cell type strongly expressing Prox1 in the adult mouse retina, and establish Prox1 as a marker of AII amacrine cells.
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Affiliation(s)
- Luis Pérez de Sevilla Müller
- Departments of Neurobiology, Medicine and Ophthalmology, David Geffen School of Medicine at Los Angeles, University of California, Los AngelesLos Angeles, CA, USA
| | - Shaghauyegh S Azar
- Departments of Neurobiology, Medicine and Ophthalmology, David Geffen School of Medicine at Los Angeles, University of California, Los AngelesLos Angeles, CA, USA
| | - Janira de Los Santos
- Departments of Neurobiology, Medicine and Ophthalmology, David Geffen School of Medicine at Los Angeles, University of California, Los AngelesLos Angeles, CA, USA
| | - Nicholas C Brecha
- Departments of Neurobiology, Medicine and Ophthalmology, David Geffen School of Medicine at Los Angeles, University of California, Los AngelesLos Angeles, CA, USA.,Stein Eye Institute, David Geffen School of Medicine at Los Angeles, University of California, Los AngelesLos Angeles, CA, USA.,CURE Digestive Diseases Research Center, David Geffen School of Medicine at Los Angeles, University of California, Los AngelesLos Angeles, CA, USA.,Veterans Administration Greater Los Angeles Health SystemLos Angeles, CA, USA
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Abstract
This chapter considers some of the challenges in obtaining accurate and consistent estimates of neuronal population size in the mouse retina, in order to identify the genetic control of cell number through QTL mapping and candidate gene analysis. We first discuss a variety of best practices for analyzing large numbers of recombinant inbred strains of mice over the course of a year in order to amass a satisfactory dataset for QTL mapping. We then consider the relative merits of using average cell density versus estimated total cell number as the target trait to be assessed, and why estimates of heritability may differ for these two traits when studying the retina in whole-mount preparations. Using our dataset on cell number for 12 different retinal cell types across the AXB/BXA recombinant inbred strain set as an example, we briefly review the QTL identified and their relationship to one another. Finally, we discuss our strategies for parsing QTL in order to identify prospective candidate genes, and how those candidates may in turn be dissected to identify causal regulatory or coding variants. By identifying the genetic determinants of nerve cell number in this fashion, we can then explore their roles in modulating developmental processes that underlie the formation of the retinal architecture.
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Reese BE, Keeley PW. Genomic control of neuronal demographics in the retina. Prog Retin Eye Res 2016; 55:246-259. [PMID: 27492954 DOI: 10.1016/j.preteyeres.2016.07.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 07/21/2016] [Accepted: 07/28/2016] [Indexed: 12/22/2022]
Abstract
The mature retinal architecture is composed of various types of neuron, each population differing in size and constrained to particular layers, wherein the cells achieve a characteristic patterning in their local organization. These demographic features of retinal nerve cell populations are each complex traits controlled by multiple genes affecting different processes during development, and their genetic determinants can be dissected by correlating variation in these traits with their genomic architecture across recombinant-inbred mouse strains. Using such a resource, we consider how the variation in the numbers of twelve different types of retinal neuron are independent of one another, including those sharing transcriptional regulation as well as those that are synaptically-connected, each mapping to distinct genomic loci. Using the populations of two retinal interneurons, the horizontal cells and the cholinergic amacrine cells, we present in further detail examples where the variation in neuronal number, as well as the variation in mosaic patterning or in laminar positioning, each maps to discrete genomic loci where allelic variants modulating these features must be present. At those loci, we identify candidate genes which, when rendered non-functional, alter those very demographic properties, and in turn, we identify candidate coding or regulatory variants that alter protein structure or gene expression, respectively, being prospective contributors to the variation in phenotype. This forward-genetic approach provides an alternative means for dissecting the molecular genetic control of neuronal population dynamics, with each genomic locus serving as a causal anchor from which we may ultimately understand the developmental principles responsible for the control of those traits.
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Affiliation(s)
- Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, CA 93106-5060, USA; Departments of Psychological & Brain Sciences, University of California, Santa Barbara, CA 93106-9660, USA.
| | - Patrick W Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, CA 93106-5060, USA; Departments of Molecular, Cellular & Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA
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15
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Reese BE, Keeley PW, Lee SCS, Whitney IE. Developmental plasticity of dendritic morphology and the establishment of coverage and connectivity in the outer retina. Dev Neurobiol 2015; 71:1273-85. [PMID: 21557509 DOI: 10.1002/dneu.20903] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Developing retinal neurons differentiate their distinctive dendritic morphologies through cell-intrinsic instructions and cellular interactions within the local environment. This review examines the contributions of interactions with afferents and with homotypic neighbors upon the dendritic morphogenesis of retinal bipolar cells in four different mouse models that modulate the frequency of these interactions. Comparisons with horizontal cell differentiation are discussed, and differences between the dendritic plasticity within the outer versus inner plexiform layers are highlighted. Finally, the developmental plasticity of the bipolar and horizontal cells is considered in light of the natural variation in afferent and target cell number, ensuring a uniformity of coverage and connectivity across the retinal surface.
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Affiliation(s)
- Benjamin E Reese
- Neuroscience Research Institute and Departments of Psychology and Molecular, Cellular and Developmental Biology, University of California at Santa Barbara, Santa Barbara, CA 93106-5060.
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Whitney IE, Kautzman AG, Reese BE. Alternative splicing of the LIM-homeodomain transcription factor Isl1 in the mouse retina. Mol Cell Neurosci 2015; 65:102-13. [PMID: 25752730 DOI: 10.1016/j.mcn.2015.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Revised: 02/12/2015] [Accepted: 03/05/2015] [Indexed: 11/25/2022] Open
Abstract
Islet-1 (Isl1) is a LIM-homeodomain (LIM-HD) transcription factor that functions in a combinatorial manner with other LIM-HD proteins to direct the differentiation of distinct cell types within the central nervous system and many other tissues. A study of pancreatic cell lines showed that Isl1 is alternatively spliced generating a second isoform, Isl1β, which is missing 23 amino acids within the C-terminal region. This study examines the expression of the canonical and alternative Isl1 transcripts across other tissues, in particular, within the retina, where Isl1 is required for the differentiation of multiple neuronal cell types. The alternative splicing of Isl1 is shown to occur in multiple tissues, but the relative abundance of Isl1α and Isl1β expression varies greatly across them. In most tissues, Isl1α is the more abundant transcript, but in others the transcripts are expressed equally, or the alternative splice variant is dominant. Within the retina, differential expression of the two Isl1 transcripts increases as a function of development, with dynamic changes in expression peaking at E16.5 and again at P10. At the cellular level, individual retinal ganglion cells vary in their expression, with a subset of small-to-medium sized cells expressing only the alternative isoform. The functional significance of the difference in protein sequence between the two Isl1 isoforms was also assessed using a luciferase assay, demonstrating that the alternative isoform forms a less effective transcriptional complex for activating gene expression. These results demonstrate the differential presence of the canonical and alternative isoforms of Isl1 amongst retinal ganglion cell classes. As Isl1 participates in the differentiation of multiple cell types within the CNS, the present results support a role for alternative splicing in the establishment of cellular diversity in the developing nervous system.
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Affiliation(s)
- Irene E Whitney
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, United States; Department of Molecular, Cellular and Developmental Biology, University of California at Santa Barbara, Santa Barbara, CA 93106-9625, United States.
| | - Amanda G Kautzman
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, United States; Department of Psychological & Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA 93106-9660, United States.
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, United States; Department of Psychological & Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA 93106-9660, United States.
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Sox2 regulates cholinergic amacrine cell positioning and dendritic stratification in the retina. J Neurosci 2014; 34:10109-21. [PMID: 25057212 DOI: 10.1523/jneurosci.0415-14.2014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The retina contains two populations of cholinergic amacrine cells, one positioned in the ganglion cell layer (GCL) and the other in the inner nuclear layer (INL), that together comprise ∼1/2 of a percent of all retinal neurons. The present study examined the genetic control of cholinergic amacrine cell number and distribution between these two layers. The total number of cholinergic amacrine cells was quantified in the C57BL/6J and A/J inbred mouse strains, and in 25 recombinant inbred strains derived from them, and variations in their number and ratio (GCL/INL) across these strains were mapped to genomic loci. The total cholinergic amacrine cell number was found to vary across the strains, from 27,000 to 40,000 cells, despite little variation within individual strains. The number of cells was always lower within the GCL relative to the INL, and the sizes of the two populations were strongly correlated, yet there was variation in their ratio between the strains. Approximately 1/3 of that variation in cell ratio was mapped to a locus on chromosome 3, where Sex determining region Y box 2 (Sox2) was identified as a candidate gene due to the presence of a 6-nucleotide insertion in the protein-coding sequence in C57BL/6J and because of robust and selective expression in cholinergic amacrine cells. Conditionally deleting Sox2 from the population of nascent cholinergic amacrine cells perturbed the normal ratio of cells situated in the GCL versus the INL and induced a bistratifying morphology, with dendrites distributed to both ON and OFF strata within the inner plexiform layer.
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Keeley PW, Madsen NR, St John AJ, Reese BE. Programmed cell death of retinal cone bipolar cells is independent of afferent or target control. Dev Biol 2014; 394:191-6. [PMID: 25169191 DOI: 10.1016/j.ydbio.2014.08.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 08/08/2014] [Accepted: 08/18/2014] [Indexed: 11/25/2022]
Abstract
Programmed cell death contributes to the histogenesis of the nervous system, and is believed to be modulated through the sustaining effects of afferents and targets during the period of synaptogenesis. Cone bipolar cells undergo programmed cell death during development, and we confirm that the numbers of three different types are increased when the pro-apoptotic Bax gene is knocked out. When their cone afferents are selectively eliminated, or when the population of retinal ganglion cells is increased, however, cone bipolar cell number remains unchanged. Programmed cell death of the cone bipolar cell populations, therefore, may be modulated cell-intrinsically rather than via interactions with these synaptic partners.
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Affiliation(s)
- Patrick W Keeley
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
| | - Nils R Madsen
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
| | - Ace J St John
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA; Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA 93106-9660, USA.
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Reese BE, Keeley PW. Design principles and developmental mechanisms underlying retinal mosaics. Biol Rev Camb Philos Soc 2014; 90:854-76. [PMID: 25109780 DOI: 10.1111/brv.12139] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 06/24/2014] [Accepted: 07/15/2014] [Indexed: 01/26/2023]
Abstract
Most structures within the central nervous system (CNS) are composed of different types of neuron that vary in both number and morphology, but relatively little is known about the interplay between these two features, i.e. about the population dynamics of a given cell type. How such arrays of neurons are distributed within a structure, and how they differentiate their dendrites relative to each other, are issues that have recently drawn attention in the invertebrate nervous system, where the genetic and molecular underpinnings of these organizing principles are being revealed in exquisite detail. The retina is one of the few locations where these principles have been extensively studied in the vertebrate CNS, indeed, where the design principles of 'mosaic regularity' and 'uniformity of coverage' were first explicitly defined, quantified, and related to each other. Recent studies have revealed a number of genes that influence the formation of these histotypical features in the retina, including homologues of those invertebrate genes, although close inspection reveals that they do not always mediate comparable developmental processes nor elucidate fundamental design principles. The present review considers just how pervasive these features of 'mosaic regularity' and 'uniform dendritic coverage' are within the mammalian retina, discussing the means by which such features can be assessed in the mature and developing nervous system and examining the limitations associated with those assessments. We then address the extent to which these two design principles co-exist within different populations of neurons, and how they are achieved during development. Finally, we consider the neural phenotypes obtained in mutant nervous systems, to address whether a prospective gene of interest underlies those very design principles.
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Affiliation(s)
- Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, CA 93106-5060, U.S.A.,Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA 93106-9660, U.S.A
| | - Patrick W Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, CA 93106-5060, U.S.A.,Department of Molecular, Cellular & Developmental Biology, University of California, Santa Barbara, CA 93106-9625, U.S.A
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20
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Independent genomic control of neuronal number across retinal cell types. Dev Cell 2014; 30:103-9. [PMID: 24954025 DOI: 10.1016/j.devcel.2014.05.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 03/21/2014] [Accepted: 05/02/2014] [Indexed: 12/22/2022]
Abstract
The sizes of different neuronal populations within the CNS are precisely controlled, but whether neuronal number is coordinated between cell types is unknown. We examined the covariance structure of 12 different retinal cell types across 30 genetically distinct lines of mice, finding minimal covariation when comparing synaptically connected or developmentally related cell types. Variation mapped to one or more genomic loci for each cell type, but rarely were these shared, indicating minimal genetic coregulation of final number. Multiple genes, therefore, participate in the specification of the size of every population of retinal neuron, yet genetic variants work largely independent of one another during development to modulate those numbers, yielding substantial variability in the convergence ratios between pre- and postsynaptic populations. Density-dependent cellular interactions in the outer plexiform layer overcome this variability to ensure the formation of neuronal circuits that maintain constant retinal coverage and complete afferent sampling.
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21
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Pituitary tumor-transforming gene 1 regulates the patterning of retinal mosaics. Proc Natl Acad Sci U S A 2014; 111:9295-300. [PMID: 24927528 DOI: 10.1073/pnas.1323543111] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Neurons are commonly organized as regular arrays within a structure, and their patterning is achieved by minimizing the proximity between like-type cells, but molecular mechanisms regulating this process have, until recently, been unexplored. We performed a forward genetic screen using recombinant inbred (RI) strains derived from two parental A/J and C57BL/6J mouse strains to identify genomic loci controlling spacing of cholinergic amacrine cells, which is a subclass of retinal interneuron. We found conspicuous variation in mosaic regularity across these strains and mapped a sizeable proportion of that variation to a locus on chromosome 11 that was subsequently validated with a chromosome substitution strain. Using a bioinformatics approach to narrow the list of potential candidate genes, we identified pituitary tumor-transforming gene 1 (Pttg1) as the most promising. Expression of Pttg1 was significantly different between the two parental strains and correlated with mosaic regularity across the RI strains. We identified a seven-nucleotide deletion in the Pttg1 promoter in the C57BL/6J mouse strain and confirmed a direct role for this motif in modulating Pttg1 expression. Analysis of Pttg1 KO mice revealed a reduction in the mosaic regularity of cholinergic amacrine cells, as well as horizontal cells, but not in two other retinal cell types. Together, these results implicate Pttg1 in the regulation of homotypic spacing between specific types of retinal neurons. The genetic variant identified creates a binding motif for the transcriptional activator protein 1 complex, which may be instrumental in driving differential expression of downstream processes that participate in neuronal spacing.
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Abstract
Approximately 20 % of individuals with Parkinson's disease (PD) report a positive family history. Yet, a large portion of causal and disease-modifying variants is still unknown. We used exome sequencing in two affected individuals from a family with late-onset PD to identify 15 potentially causal variants. Segregation analysis and frequency assessment in 862 PD cases and 1,014 ethnically matched controls highlighted variants in EEF1D and LRRK1 as the best candidates. Mutation screening of the coding regions of these genes in 862 cases and 1,014 controls revealed several novel non-synonymous variants in both genes in cases and controls. An in silico multi-model bioinformatics analysis was used to prioritize identified variants in LRRK1 for functional follow-up. However, protein expression, subcellular localization, and cell viability were not affected by the identified variants. Although it has yet to be proven conclusively that variants in LRRK1 are indeed causative of PD, our data strengthen a possible role for LRRK1 in addition to LRRK2 in the genetic underpinnings of PD but, at the same time, highlight the difficulties encountered in the study of rare variants identified by next-generation sequencing in diseases with autosomal dominant or complex patterns of inheritance.
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Schlamp CL, Montgomery AD, Mac Nair CE, Schuart C, Willmer DJ, Nickells RW. Evaluation of the percentage of ganglion cells in the ganglion cell layer of the rodent retina. Mol Vis 2013; 19:1387-96. [PMID: 23825918 PMCID: PMC3695759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 06/25/2013] [Indexed: 11/20/2022] Open
Abstract
PURPOSE Retinal ganglion cells comprise a percentage of the neurons actually residing in the ganglion cell layer (GCL) of the rodent retina. This estimate is useful to extrapolate ganglion cell loss in models of optic nerve disease, but the values reported in the literature are highly variable depending on the methods used to obtain them. METHODS We tested three retrograde labeling methods and two immunostaining methods to calculate ganglion cell number in the mouse retina (C57BL/6). Additionally, a double-stain retrograde staining method was used to label rats (Long-Evans). The number of total neurons was estimated using a nuclear stain and selecting for nuclei that met specific criteria. Cholinergic amacrine cells were identified using transgenic mice expressing Tomato fluorescent protein. Total neurons and total ganglion cell numbers were measured in microscopic fields of 10(4) µm(2) to determine the percentage of neurons comprising ganglion cells in each field. RESULTS Historical estimates of the percentage of ganglion cells in the mouse GCL range from 36.1% to 67.5% depending on the method used. Experimentally, retrograde labeling methods yielded a combined estimate of 50.3% in mice. A retrograde method also yielded a value of 50.21% for rat retinas. Immunolabeling estimates were higher at 64.8%. Immunolabeling may introduce overestimates, however, with non-specific labeling effects, or ectopic expression of antigens in neurons other than ganglion cells. CONCLUSIONS Since immunolabeling methods may overestimate ganglion cell numbers, we conclude that 50%, which is consistently derived from retrograde labeling methods, is a reliable estimate of the ganglion cells in the neuronal population of the GCL.
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Affiliation(s)
- Cassandra L. Schlamp
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI
| | - Angela D. Montgomery
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI
| | - Caitlin E. Mac Nair
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI,Pathology and Laboratory Medicine, University of Wisconsin, Madison, WI
| | - Claudia Schuart
- University Eye Hospital, Otto-von-Guericke University, Magdeburg, Germany
| | - Daniel J. Willmer
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI,Pathology and Laboratory Medicine, University of Wisconsin, Madison, WI
| | - Robert W. Nickells
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI
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Nadeau JH, Forejt J, Takada T, Shiroishi T. Chromosome substitution strains: gene discovery, functional analysis, and systems studies. Mamm Genome 2012; 23:693-705. [PMID: 22961226 DOI: 10.1007/s00335-012-9426-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2012] [Accepted: 08/02/2012] [Indexed: 12/31/2022]
Abstract
Laboratory mice are valuable in biomedical research in part because of the extraordinary diversity of genetic resources that are available for studies of complex genetic traits and as models for human biology and disease. Chromosome substitution strains (CSSs) are important in this resource portfolio because of their demonstrated use for gene discovery, genetic and epigenetic studies, functional characterizations, and systems analysis. CSSs are made by replacing a single chromosome in a host strain with the corresponding chromosome from a donor strain. A complete CSS panel involves a total of 22 engineered inbred strains, one for each of the 19 autosomes, one each for the X and Y chromosomes, and one for mitochondria. A genome survey simply involves comparing each phenotype for each of the CSSs with the phenotypes of the host strain. The CSS panels that are available for laboratory mice have been used to dissect a remarkable variety of phenotypes and to characterize an impressive array of disease models. These surveys have revealed considerable phenotypic diversity even among closely related progenitor strains, evidence for strong epistasis and for heritable epigenetic changes. Perhaps most importantly, and presumably because of their unique genetic constitution, CSSs, and congenic strains derived from them, the genetic variants underlying quantitative trait loci (QTLs) are readily identified and functionally characterized. Together these studies show that CSSs are important resource for laboratory mice.
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Affiliation(s)
- Joseph H Nadeau
- Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA.
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Keeley PW, Sliff BJ, Lee SCS, Fuerst PG, Burgess RW, Eglen SJ, Reese BE. Neuronal clustering and fasciculation phenotype in Dscam- and Bax-deficient mouse retinas. J Comp Neurol 2012; 520:1349-64. [PMID: 22396220 DOI: 10.1002/cne.23033] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Individual types of retinal neurons are distributed to minimize proximity to neighboring cells. Many of these same cell types extend dendrites to provide coverage of the retinal surface. These two cardinal features of retinal mosaics are disrupted, for certain cell types, in mice deficient for the Down syndrome cell adhesion molecule, Dscam, exhibiting an aberrant clustering of somata and fasciculation of dendrites. The Dscam mutant mouse retina also exhibits excess numbers of these same cell types. The present study compared these two features in Dscam mutant retinas with the Bax knockout retina, in which excess numbers of two of these cell types, the melanopsin-positive retinal ganglion cells (MRGCs) and the dopaminergic amacrine cells (DACs), are also present. Whole retinas were immunolabeled for both populations, and every labeled soma was plotted. For the MRGCs, we found a gene dosage effect for Dscam, with the Dscam+/- retinas showing smaller increases in cell number, clustering, and fasciculation. Curiously, Bax-/- retinas, showing numbers of MRGCs intermediate to those found in the Dscam-/- and Dscam+/- retinas, also had clustering and fasciculation phenotypes that were intermediate to retinas with those genotypes. DACs, by comparison, showed changes in both the Dscam-/- and the Bax-/- retinas that did not correlate with their increases in DAC number. The fasciculation phenotype in the Dscam-/- retina was particularly prominent despite only modest clustering. These results demonstrate that the somal clustering and fasciculation observed in the Dscam mutant retina are not unique to Dscam deficiency and are manifested distinctively by different retinal cell types.
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Affiliation(s)
- Patrick W Keeley
- Neuroscience Research Institute, Department of Molecular, Cellular and Developmental Biology, University of California at Santa Barbara, Santa Barbara, California 93106, USA
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26
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Garrett AM, Burgess RW. Candidate molecular mechanisms for establishing cell identity in the developing retina. Dev Neurobiol 2012; 71:1258-72. [PMID: 21630473 DOI: 10.1002/dneu.20926] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the developing nervous system, individual neurons must occupy appropriate positions within circuits. This requires that these neurons recognize and form connections with specific pre- and postsynaptic partners. Cellular recognition is also required for the spacing of cell bodies and the arborization of dendrites, factors that determine the inputs onto a given neuron. These issues are particularly evident in the retina, where different types of neurons are evenly spaced relative to other cells of the same type. This establishes a reiterated columnar circuitry resembling the insect retina. Establishing these mosaic patterns requires that cells of a given type (homotypic cells) be able to sense their neighbors. Therefore, both synaptic specificity and mosaic spacing require cellular identifiers. In synaptic specificity, recognition often occurs between different types of cells in a pre- and postsynaptic pairing. In mosaic spacing, recognition is often occurring between different cells of the same type, orhomotypic self-recognition. Dendritic arborization can require recognition of different neurites of the same cell, or isoneuronal self-recognition. The retina is an extremely amenable system for studying the molecular identifiers that drive these various forms of recognition. The different neuronal types in the retina are well defined, and the genetic tools for marking cell types are increasingly available. In this review we will summarize retinal anatomy and describe cell types in the retina and how they are defined. We will then describe the requirements of a recognition code and discuss newly emerging candidate molecular mechanisms for recognition that may meet these requirements.
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Lu'o'ng KVQ, Nguyên LTH. Thiamine and Parkinson's disease. J Neurol Sci 2012; 316:1-8. [PMID: 22385680 DOI: 10.1016/j.jns.2012.02.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 02/03/2012] [Accepted: 02/08/2012] [Indexed: 11/20/2022]
Abstract
Parkinson's disease (PD) is the second most common form of neurodegeneration in the elderly population. PD is clinically characterized by tremors, rigidity, slowness of movement and postural imbalance. A significant association has been demonstrated between PD and low levels of thiamine in the serum, which suggests that elevated thiamine levels might provide protection against PD. Genetic studies have helped identify a number of factors that link thiamine to PD pathology, including the DJ-1 gene, excitatory amino acid transporters (EAATs), the α-ketoglutarate dehydrogenase complex (KGDHC), coenzyme Q10 (CoQ10 or ubiquinone), lipoamide dehydrogenase (LAD), chromosome 7, transcription factor p53, the renin-angiotensin system (RAS), heme oxygenase-1 (HO-1), and poly(ADP-ribose) polymerase-1 gene (PARP-1). Thiamine has also been implicated in PD through its effects on L-type voltage-sensitive calcium channels (L-VSCC), matrix metalloproteinases (MMPs), prostaglandins (PGs), cyclooxygenase-2 (COX-2), reactive oxygen species (ROS), and nitric oxide synthase (NOS). Recent studies highlight a possible relationship between thiamine and PD. Genetic studies provide opportunities to determine which proteins may link thiamine to PD pathology. Thiamine can also act through a number of non-genomic mechanisms that include protein expression, oxidative stress, inflammation, and cellular metabolism. Further studies are needed to determine the benefits of using thiamine as a treatment for PD.
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Hudson BD, Beazley M, Szczesniak AM, Straiker A, Kelly MEM. Indirect sympatholytic actions at β-adrenoceptors account for the ocular hypotensive actions of cannabinoid receptor agonists. J Pharmacol Exp Ther 2011; 339:757-67. [PMID: 21885619 PMCID: PMC11047145 DOI: 10.1124/jpet.111.185769] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 08/22/2011] [Indexed: 01/27/2023] Open
Abstract
Intraocular pressure (IOP) is the primary risk factor for glaucoma, a blinding eye disease. Cannabinoid agonists have long been known to decrease IOP, suggesting they may be useful in glaucoma treatment. However, the specific mechanism by which cannabinoids generate this ocular hypotensive effect remains unknown. The current evidence suggests the cannabinoids reduce IOP through actions at cannabinoid 1 (CB(1)) receptors within the eye, and adrenergic receptors (ARs) may also contribute to this action of cannabinoids. Considering this, the present study aimed to elucidate the mechanism behind the ocular hypotensive properties of cannabinoids through the use of mice genetically lacking either cannabinoid receptors or βARs. Cannabinoid agonists, βAR antagonists, and βAR agonists decreased IOP in wild-type mice and CB(2)(-/-) mice. In contrast, none of these compounds were found to reduce IOP in βAR(-/-) or CB(1)(-/-) mice. Desensitization of the βARs and depletion of catecholamines in wild-type mice also eliminated the ability of the cannabinoid agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate (WIN 55,212-2) to reduce IOP, strongly implicating a role for both βARs and catecholamines in the ocular hypotensive properties of cannabinoids. Finally, CB(1) receptors were shown to colocalize with tyrosine hydroxylase, a marker for adrenergic neurons. Taken together, these findings suggest that βARs are required for the ocular hypotensive properties of cannabinoids, and cannabinoids reduce IOP by acting as indirect sympatholytics and inhibiting norepinephrine release within the eye.
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Affiliation(s)
- Brian D Hudson
- Department of Pharmacology, Sir Charles Tupper Building, Dalhousie University, 5850 College St. Halifax, NS, Canada B3H1X5
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Overexpression of neurotrophin-3 stimulates a second wave of dopaminergic amacrine cell genesis after birth in the mouse retina. J Neurosci 2011; 31:12663-73. [PMID: 21880927 DOI: 10.1523/jneurosci.1100-11.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Dopaminergic amacrine (DA) cells play multiple and important roles in retinal function. Neurotrophins are known to modulate the number and morphology of DA cells, but the underlying regulatory mechanisms are unclear. Here, we investigate how neurotrophin-3 (NT-3) regulates DA cell density in the mouse retina. We demonstrate that overexpression of NT-3 upregulates DA cell number and leads to a consequent increase in the density of DA cell dendrites. To examine the mechanisms of DA cell density increase, we further investigate the effect of NT-3 overexpression on retinal apoptosis and mitosis during development. We find that NT-3 does not affect the well known wave of retinal cell apoptosis that normally occurs during the first 2 weeks after birth. Instead, overexpression of NT-3 promotes additional mitosis of DA cells at postnatal day 4, but does not affect cell mitosis before birth, the peak period of amacrine cell genesis in wild-type retinas. We next show that retinal explants cultured from birth to day 7 without extra NT-3 produced by lens exhibit similar number of DA cells as in wild type, further supporting the notion that postnatal overexpression of lens-derived NT-3 affects DA cell number. Moreover, the additional mitosis after birth in NT-3-overexpressing mice does not occur in calretinin-positive amacrine cells or PKC-positive rod ON bipolar cells. Thus, the NT-3-triggered wave of cell mitosis after birth is specific for the retinal DA cells.
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Whitney IE, Raven MA, Lu L, Williams RW, Reese BE. A QTL on chromosome 10 modulates cone photoreceptor number in the mouse retina. Invest Ophthalmol Vis Sci 2011; 52:3228-36. [PMID: 21330668 DOI: 10.1167/iovs.10-6693] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
PURPOSE This investigation examines the genetic sources of marked variation in cone photoreceptor number among inbred lines of mice, identifying candidate genes that may control the proliferation, differentiation, or survival of this neuronal population. METHODS Cone photoreceptor populations were counted in C57BL/6J (B6/J) and A/J strains, and 26 recombinant inbred (RI) strains derived from them. Eyes from RI strains were also collected for microarray analysis. Quantitative trait locus (QTL) analysis was carried out by simple and composite interval mapping and validated using a consomic line. Candidate genes were evaluated based on genetic variance between the parental strains and analysis of gene expression. Expression data, deposited in GeneNetwork (www.GeneNetwork.org), were used to generate a coexpression network of established cone photoreceptor genes as a reference standard. RESULTS B6/J has 70% more cone photoreceptors than A/J. A significant QTL was mapped to chromosome 10 (Chr 10) and confirmed using B6.A<10> mice. Of 19 positional candidate genes, one-the myeloblastosis oncogene (Myb)-stood out. Myb has a potentially damaging missense mutation, high retinal expression, and a known role in cell proliferation. The ectonucleotide pyrophosphatase/phosphodiesterase 1 gene (Enpp1) was a second strong candidate, with an expression pattern that covaried with cone photoreceptors and that was differentially expressed between the parental strains. Enpp1 and several other candidate genes covaried with multiple genes within the cone photoreceptor gene network. CONCLUSIONS The mouse retina shows marked variation in cone photoreceptor number, some of which must be controlled by polymorphisms in a gene or genes on Chr 10.
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Affiliation(s)
- Irene E Whitney
- Neuroscience Research Institute and Department of Molecular, Cell, and Developmental Biology, University of California, Santa Barbara, California 93106-5060, USA
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Abstract
Neuronal populations display conspicuous variability in their size among individuals, but the genetic sources of this variation are largely undefined. We demonstrate a large and highly heritable variation in neuron number within the mouse retina, affecting a critical population of interneurons, the horizontal cells. Variation in the size of this population maps to the distal end of chromosome (Chr) 13, a region homologous to human Chr 5q11.1-11.2. This region contains two genes known to modulate retinal cell number. Using conditional knock-out mice, we demonstrate that one of these genes, the LIM homeodomain gene Islet-1 (Isl1), plays a role in regulating horizontal cell number. Genetic differences in Isl1 expression are high during the period of horizontal cell production, and cis-regulation of Isl1 expression within the retina is demonstrated directly. We identify a single nucleotide polymorphism in the 5' UTR of Isl1 that creates an E-box sequence as a candidate causal variant contributing to this variation in horizontal cell number.
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Reese BE. Development of the retina and optic pathway. Vision Res 2010; 51:613-32. [PMID: 20647017 DOI: 10.1016/j.visres.2010.07.010] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 07/04/2010] [Accepted: 07/13/2010] [Indexed: 12/30/2022]
Abstract
Our understanding of the development of the retina and visual pathways has seen enormous advances during the past 25years. New imaging technologies, coupled with advances in molecular biology, have permitted a fuller appreciation of the histotypical events associated with proliferation, fate determination, migration, differentiation, pathway navigation, target innervation, synaptogenesis and cell death, and in many instances, in understanding the genetic, molecular, cellular and activity-dependent mechanisms underlying those developmental changes. The present review considers those advances associated with the lineal relationships between retinal nerve cells, the production of retinal nerve cell diversity, the migration, patterning and differentiation of different types of retinal nerve cells, the determinants of the decussation pattern at the optic chiasm, the formation of the retinotopic map, and the establishment of ocular domains within the thalamus.
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Affiliation(s)
- Benjamin E Reese
- Neuroscience Research Institute and Department of Psychology, University of California at Santa Barbara, Santa Barbara, CA 93106-5060, USA.
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Keeley PW, Reese BE. Morphology of dopaminergic amacrine cells in the mouse retina: independence from homotypic interactions. J Comp Neurol 2010; 518:1220-31. [PMID: 20148440 PMCID: PMC2865197 DOI: 10.1002/cne.22270] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
To determine the role of homotypic interactions between neighboring dopaminergic amacrine (DA) cells upon dendritic morphogenesis, the morphology of single cells was examined relative to the positioning of all neighboring homotypic cells. For each labeled cell, the dendritic field was reconstructed, its Voronoi domain was calculated, and the two were related. The dendritic fields of DA cells were observed to be large, sparse, and highly irregular. Dendrites readily overlapped those of neighboring cells, showing no evidence for dendritic tiling or inter-digitation consistent with homotypic repulsion or avoidance. Furthermore, a direct comparison of dendritic field area with the Voronoi domain area of the same cell showed no evidence for dendritic growth being constrained or biased by the local distribution of homotypic neighbors in wild-type retinas. A comparison of the processes of adjacent filled cells confirmed their immediate proximity to one another within the inner plexiform layer, indicating that they do not engage in mutual avoidance by coursing at different depths. Together, these results suggest that the morphogenesis of DA cells is independent of homotypic interactions. However, in the absence of the pro-apoptotic Bax gene, which yields a fourfold increase in DA cell number, a small but significant reduction in dendritic field size was obtained, although not so great as would be predicted by the increase in density. The present results are considered in light of recent studies on the role of cell adhesion molecules expressed by developing DA cells.
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Affiliation(s)
- Patrick W Keeley
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106-9625, USA
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A single nucleotide polymorphism in the Bax gene promoter affects transcription and influences retinal ganglion cell death. ASN Neuro 2010; 2:e00032. [PMID: 20360947 PMCID: PMC2847828 DOI: 10.1042/an20100003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 02/24/2010] [Accepted: 03/02/2010] [Indexed: 11/17/2022] Open
Abstract
Pro-apoptotic Bax is essential for RGC (retinal ganglion cell)
death. Gene dosage experiments in mice, yielding a single wild-type
Bax allele, indicated that genetic background was able to
influence the cell death phenotype. DBA/2JBax+/− mice exhibited complete resistance to nerve damage after 2 weeks
(similar to Bax−/− mice), but 129B6Bax+/− mice exhibited significant cell loss (similar to wild-type mice). The
different cell death phenotype was associated with the level of
Bax expression, where 129B6 neurons had twice the level of
endogenous Bax mRNA and protein as DBA/2J neurons. Sequence
analysis of the Bax promoters between these strains revealed a
single nucleotide polymorphism (T129B6 to CDBA/2J) at
position −515. A 1.5- to 2.5-fold increase in transcriptional
activity was observed from the 129B6 promoter in transient transfection assays
in a variety of cell types, including RGC5 cells derived from rat RGCs. Since
this polymorphism occurred in a p53 half-site, we investigated the requirement
of p53 for the differential transcriptional activity. Differential
transcriptional activity from either 129B6 or DBA/2J Bax
promoters were unaffected in p53−/− cells, and
addition of exogenous p53 had no further effect on this difference, thus a role
for p53 was excluded. Competitive electrophoretic mobility-shift assays
identified two DNA–protein complexes that interacted with the
polymorphic region. Those forming Complex 1 bound with higher affinity to the
129B6 polymorphic site, suggesting that these proteins probably comprised a
transcriptional activator complex. These studies implicated quantitative
expression of the Bax gene as playing a possible role in
neuronal susceptibility to damaging stimuli.
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Abstract
To establish dendritic arbors that integrate properly into a neural circuit, neurons must rely on cues from the local environment. The neurons presynaptic to these arbors, the afferents, are one potential source of these cues, but the particular dendritic features they regulate remain unclear. Retinal bipolar cells can be classified by the type of photoreceptor, cone or rod, forming synaptic contacts with their dendrites, suggesting a potential role of these afferents in shaping the bipolar cell dendritic arbor. In the present investigation, the role of photoreceptors in directing the differentiation of bipolar cells has been studied using two genetically modified "coneless" and "conefull" mice. Single cone (Type 7/CB4a) and rod bipolar cells were labeled with DiI to reveal the entire dendritic arbor and subsequently analyzed for several morphological features. For both cone and rod bipolar cells, the dendritic field area, number of dendritic terminals, and stratification of terminals in the outer plexiform layer were comparable among coneless, conefull, and wild-type retinas, and the overall morphological appearance of each type of cell was essentially conserved, indicating an independence from afferent specification. The presence of normal afferents was, however, found to be critical for the proper spatial distribution of dendritic terminals, exhibiting a clustered distribution for the cone bipolar cells and a dispersed distribution for the rod bipolar cells. These results demonstrate a selectivity in the afferent dependency of bipolar cell differentiation, their basic morphogenetic plan commanded cell intrinsically, and their fine terminal connectivity directed by the afferents themselves.
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Fuerst PG, Bruce F, Tian M, Wei W, Elstrott J, Feller MB, Erskine L, Singer JH, Burgess RW. DSCAM and DSCAML1 function in self-avoidance in multiple cell types in the developing mouse retina. Neuron 2009; 64:484-97. [PMID: 19945391 DOI: 10.1016/j.neuron.2009.09.027] [Citation(s) in RCA: 183] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2009] [Indexed: 02/04/2023]
Abstract
DSCAM and DSCAM-LIKE1 (DSCAML1) serve diverse neurodevelopmental functions, including axon guidance, synaptic adhesion, and self-avoidance, depending on the species, cell type, and gene family member studied. We examined the function of DSCAM and DSCAML1 in the developing mouse retina. In addition to a subset of amacrine cells, Dscam was expressed in most retinal ganglion cells (RGCs). RGCs had fasciculated dendrites and clumped cell bodies in Dscam(-/-) mice, suggesting a role in self-avoidance. Dscaml1 was expressed in the rod circuit, and mice lacking Dscaml1 had fasciculated rod bipolar cell dendrites and clumped AII amacrine cell bodies, also indicating a role in self-avoidance. Neurons in Dscam or Dscaml1 mutant retinas stratified their processes appropriately in synaptic laminae in the inner plexiform layer, and functional synapses formed in the rod circuit in mice lacking Dscaml1. Therefore, DSCAM and DSCAML1 function similarly in self-avoidance, and are not essential for synaptic specificity in the mouse retina.
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Templeton JP, Nassr M, Vazquez-Chona F, Freeman-Anderson NE, Orr WE, Williams RW, Geisert EE. Differential response of C57BL/6J mouse and DBA/2J mouse to optic nerve crush. BMC Neurosci 2009; 10:90. [PMID: 19643015 PMCID: PMC2727955 DOI: 10.1186/1471-2202-10-90] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Accepted: 07/30/2009] [Indexed: 01/02/2023] Open
Abstract
Background Retinal ganglion cell (RGC) death is the final consequence of many blinding diseases, where there is considerable variation in the time course and severity of RGC loss. Indeed, this process appears to be influenced by a wide variety of genetic and environmental factors. In this study we explored the genetic basis for differences in ganglion cell death in two inbred strains of mice. Results We found that RGCs are more susceptible to death following optic nerve crush in C57BL/6J mice (54% survival) than in DBA/2J mice (62% survival). Using the Illumina Mouse-6 microarray, we identified 1,580 genes with significant change in expression following optic nerve crush in these two strains of mice. Our analysis of the changes occurring after optic nerve crush demonstrated that the greatest amount of change (44% of the variance) was due to the injury itself. This included changes associated with ganglion cell death, reactive gliosis, and abortive regeneration. The second pattern of gene changes (23% of the variance) was primarily related to differences in gene expressions observed between the C57BL/6J and DBA/2J mouse strains. The remaining changes in gene expression represent interactions between the effects of optic nerve crush and the genetic background of the mouse. We extracted one genetic network from this dataset that appears to be related to tissue remodeling. One of the most intriguing sets of changes included members of the crystallin family of genes, which may represent a signature of pathways modulating the susceptibility of cells to death. Conclusion Differential responses to optic nerve crush between two widely used strains of mice were used to define molecular networks associated with ganglion cell death and reactive gliosis. These results form the basis for our continuing interest in the modifiers of retinal injury.
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Affiliation(s)
- Justin P Templeton
- Department of Ophthalmology, University of Tennessee Health Science Center, Memphis TN, 38163, USA.
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