1
|
Keeley PW, Trod S, Gamboa BN, Coffey PJ, Reese BE. Nfia Is Critical for AII Amacrine Cell Production: Selective Bipolar Cell Dependencies and Diminished ERG. J Neurosci 2023; 43:8367-8384. [PMID: 37775301 PMCID: PMC10711738 DOI: 10.1523/jneurosci.1099-23.2023] [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: 06/13/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/01/2023] Open
Abstract
The nuclear factor one (NFI) transcription factor genes Nfia, Nfib, and Nfix are all enriched in late-stage retinal progenitor cells, and their loss has been shown to retain these progenitors at the expense of later-generated retinal cell types. Whether they play any role in the specification of those later-generated fates is unknown, but the expression of one of these, Nfia, in a specific amacrine cell type may intimate such a role. Here, Nfia conditional knockout (Nfia-CKO) mice (both sexes) were assessed, finding a massive and largely selective absence of AII amacrine cells. There was, however, a partial reduction in type 2 cone bipolar cells (CBCs), being richly interconnected to AII cells. Counts of dying cells showed a significant increase in Nfia-CKO retinas at postnatal day (P)7, after AII cell numbers were already reduced but in advance of the loss of type 2 CBCs detected by P10. Those results suggest a role for Nfia in the specification of the AII amacrine cell fate and a dependency of the type 2 CBCs on them. Delaying the conditional loss of Nfia to the first postnatal week did not alter AII cell number nor differentiation, further suggesting that its role in AII cells is solely associated with their production. The physiological consequences of their loss were assessed using the ERG, finding the oscillatory potentials to be profoundly diminished. A slight reduction in the b-wave was also detected, attributed to an altered distribution of the terminals of rod bipolar cells, implicating a role of the AII amacrine cells in constraining their stratification.SIGNIFICANCE STATEMENT The transcription factor NFIA is shown to play a critical role in the specification of a single type of retinal amacrine cell, the AII cell. Using an Nfia-conditional knockout mouse to eliminate this population of retinal neurons, we demonstrate two selective bipolar cell dependencies on the AII cells; the terminals of rod bipolar cells become mis-stratified in the inner plexiform layer, and one type of cone bipolar cell undergoes enhanced cell death. The physiological consequence of this loss of the AII cells was also assessed, finding the cells to be a major contributor to the oscillatory potentials in the electroretinogram.
Collapse
Affiliation(s)
- Patrick W Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Stephanie Trod
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Bruno N Gamboa
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Pete J Coffey
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
| | - Benjamin E Reese
- Neuroscience Research Institute, University of California, Santa Barbara, California 93106-5060
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, California 93106-5060
| |
Collapse
|
2
|
D'Souza SP, Upton BA, Eldred KC, Glass I, Grover K, Ahmed A, Ngyuen MT, Gamlin P, Lang RA. Developmental adaptation of rod photoreceptor number via photoreception in melanopsin (OPN4) retinal ganglion cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.24.554675. [PMID: 37662196 PMCID: PMC10473760 DOI: 10.1101/2023.08.24.554675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Photoreception, a form of sensory experience, is essential for normal development of the mammalian visual system. Detecting photons during development is a prerequisite for visual system function - from vision's first synapse at the cone pedicle and maturation of retinal vascular networks, to transcriptional establishment and maturation of cell types within the visual cortex. Consistent with this theme, we find that the lighting environment regulates developmental rod photoreceptor apoptosis via OPN4-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs). Using a combination of genetics, sensory environment manipulations, and computational approaches, we establish a molecular pathway in which light-dependent glutamate release from ipRGCs is detected via a transiently expressed kainate receptor (GRIK3) in immature rods localized to the inner retina. Communication between ipRGCs and nascent inner retinal rods appears to be mediated by unusual hybrid neurites projecting from ipRGCs that sense light before eye-opening. These structures, previously referred to as outer retinal dendrites (ORDs), span the ipRGC-immature rod distance over the first postnatal week and contain the machinery for sensory detection (melanopsin, OPN4) and axonal/anterograde neurotransmitter release (Synaptophysin, and VGLUT2). Histological and computational assessment of human mid-gestation development reveal conservation of several hallmarks of an ipRGC-to-immature rod pathway, including displaced immature rods, transient GRIK3 expression in the rod lineage, and the presence of ipRGCs with putative neurites projecting deep into the developing retina. Thus, this analysis defines a retinal retrograde signaling pathway that links the sensory environment to immature rods via ipRGC photoreceptors, allowing the visual system to adapt to distinct lighting environments priory to eye-opening.
Collapse
|
3
|
Fitzpatrick MJ, Kerschensteiner D. Homeostatic plasticity in the retina. Prog Retin Eye Res 2022; 94:101131. [PMID: 36244950 DOI: 10.1016/j.preteyeres.2022.101131] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/25/2022] [Accepted: 09/28/2022] [Indexed: 02/07/2023]
Abstract
Vision begins in the retina, whose intricate neural circuits extract salient features of the environment from the light entering our eyes. Neurodegenerative diseases of the retina (e.g., inherited retinal degenerations, age-related macular degeneration, and glaucoma) impair vision and cause blindness in a growing number of people worldwide. Increasing evidence indicates that homeostatic plasticity (i.e., the drive of a neural system to stabilize its function) can, in principle, preserve retinal function in the face of major perturbations, including neurodegeneration. Here, we review the circumstances and events that trigger homeostatic plasticity in the retina during development, sensory experience, and disease. We discuss the diverse mechanisms that cooperate to compensate and the set points and outcomes that homeostatic retinal plasticity stabilizes. Finally, we summarize the opportunities and challenges for unlocking the therapeutic potential of homeostatic plasticity. Homeostatic plasticity is fundamental to understanding retinal development and function and could be an important tool in the fight to preserve and restore vision.
Collapse
|
4
|
West ER, Lapan SW, Lee C, Kajderowicz KM, Li X, Cepko CL. Spatiotemporal patterns of neuronal subtype genesis suggest hierarchical development of retinal diversity. Cell Rep 2022; 38:110191. [PMID: 34986354 DOI: 10.1016/j.celrep.2021.110191] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 10/21/2021] [Accepted: 12/08/2021] [Indexed: 11/26/2022] Open
Abstract
How do neuronal subtypes emerge during development? Recent molecular studies have profiled existing neuronal diversity, but neuronal subtype genesis remains elusive. The 15 types of mouse retinal bipolar interneurons are characterized by distinct functions, morphologies, and transcriptional profiles. Here, we develop a comprehensive spatiotemporal map of bipolar subtype genesis in the murine retina. Combining multiplexed detection of 16 RNA markers with timed delivery of 5-ethynyl uridine (EdU) and bromodeoxyuridine (BrdU), we analyze more than 30,000 single cells in full retinal sections to classify all bipolar subtypes and their birthdates. We find that bipolar subtype birthdates are ordered and follow a centrifugal developmental axis. Spatial analysis reveals a striking wave pattern of bipolar subtype birthdates, and lineage analyses suggest clonal restriction on homotypic subtype production. These results inspire a hierarchical developmental model, with ordered subtype genesis within lineages. Our results provide insight into neuronal subtype development and establish a framework for studying subtype diversification.
Collapse
Affiliation(s)
- Emma R West
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Sylvain W Lapan
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - ChangHee Lee
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Kathrin M Kajderowicz
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Xihao Li
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Constance L Cepko
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
| |
Collapse
|
5
|
West ER, Cepko CL. Development and diversification of bipolar interneurons in the mammalian retina. Dev Biol 2021; 481:30-42. [PMID: 34534525 DOI: 10.1016/j.ydbio.2021.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 08/31/2021] [Accepted: 09/13/2021] [Indexed: 12/18/2022]
Abstract
The bipolar interneurons of the mammalian retina have evolved as a diverse set of cells with distinct subtype characteristics, which reflect specialized contributions to visual circuitry. Fifteen subtypes of bipolar interneurons have been identified in the mouse retina, each with characteristic gene expression, morphology, and light responses. This review provides an overview of the developmental events that underlie the generation of the diverse bipolar cell class, summarizing the current knowledge of genetic programs that establish and maintain bipolar subtype fates, as well as the events that shape the final distribution of bipolar subtypes. With much left to be discovered, bipolar interneurons present an ideal model system for studying the interplay between cell-autonomous and non-cell-autonomous mechanisms that influence neuronal subtype development within the central nervous system.
Collapse
Affiliation(s)
- Emma R West
- Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA
| | - Constance L Cepko
- Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA.
| |
Collapse
|
6
|
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.
Collapse
|
7
|
Simmons AB, Camerino MJ, Clemons MR, Sukeena JM, Bloomsburg S, Borghuis BG, Fuerst PG. Increased density and age-related sharing of synapses at the cone to OFF bipolar cell synapse in the mouse retina. J Comp Neurol 2019; 528:1140-1156. [PMID: 31721194 DOI: 10.1002/cne.24810] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 10/22/2019] [Accepted: 11/06/2019] [Indexed: 11/09/2022]
Abstract
Neural circuits in the adult nervous system are characterized by stable, cell type-specific patterns of synaptic connectivity. In many parts of the nervous system these patterns are established during development through initial over-innervation by multiple pre- or postsynaptic targets, followed by a process of refinement that takes place during development and is in many instances activity dependent. Here we report on an identified synapse in the mouse retina, the cone photoreceptor➔type 4 bipolar cell (BC4) synapse, and show that its development is distinctly different from the common motif of over-innervation followed by refinement. Indeed, the majority of cones are contacted by single BC4 throughout development, but are contacted by multiple BC4s through ongoing dendritic elaboration between 1 and 6 months of age-well into maturity. We demonstrate that cell density drives contact patterns downstream of single cones in Bax null mice and may serve to maintain constancy in both the dendritic and axonal projective field.
Collapse
Affiliation(s)
- Aaron B Simmons
- Department of Biological Sciences, University of Idaho, Moscow, Idaho
| | | | - Mellisa R Clemons
- Department of Biological Sciences, University of Idaho, Moscow, Idaho
| | - Joshua M Sukeena
- Department of Biological Sciences, University of Idaho, Moscow, Idaho
| | - Samuel Bloomsburg
- Department of Biological Sciences, University of Idaho, Moscow, Idaho
| | - Bart G Borghuis
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville
| | - Peter G Fuerst
- Department of Biological Sciences, University of Idaho, Moscow, Idaho.,WWAMI Medical Education Program, University of Washington School of Medicine, Moscow, Idaho
| |
Collapse
|
8
|
Puñal VM, Paisley CE, Brecha FS, Lee MA, Perelli RM, Wang J, O’Koren EG, Ackley CR, Saban DR, Reese BE, Kay JN. Large-scale death of retinal astrocytes during normal development is non-apoptotic and implemented by microglia. PLoS Biol 2019; 17:e3000492. [PMID: 31626642 PMCID: PMC6821132 DOI: 10.1371/journal.pbio.3000492] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 10/30/2019] [Accepted: 09/26/2019] [Indexed: 12/28/2022] Open
Abstract
Naturally occurring cell death is a fundamental developmental mechanism for regulating cell numbers and sculpting developing organs. This is particularly true in the nervous system, where large numbers of neurons and oligodendrocytes are eliminated via apoptosis during normal development. Given the profound impact of death upon these two major cell populations, it is surprising that developmental death of another major cell type—the astrocyte—has rarely been studied. It is presently unclear whether astrocytes are subject to significant developmental death, and if so, how it occurs. Here, we address these questions using mouse retinal astrocytes as our model system. We show that the total number of retinal astrocytes declines by over 3-fold during a death period spanning postnatal days 5–14. Surprisingly, these astrocytes do not die by apoptosis, the canonical mechanism underlying the vast majority of developmental cell death. Instead, we find that microglia engulf astrocytes during the death period to promote their developmental removal. Genetic ablation of microglia inhibits astrocyte death, leading to a larger astrocyte population size at the end of the death period. However, astrocyte death is not completely blocked in the absence of microglia, apparently due to the ability of astrocytes to engulf each other. Nevertheless, mice lacking microglia showed significant anatomical changes to the retinal astrocyte network, with functional consequences for the astrocyte-associated vasculature leading to retinal hemorrhage. These results establish a novel modality for naturally occurring cell death and demonstrate its importance for the formation and integrity of the retinal gliovascular network. A study of the neonatal mouse retina shows that developmental cell death of retinal astrocytes does not occur by apoptosis but is instead mediated by microglia, which kill and engulf astrocytes to effect their developmental removal.
Collapse
Affiliation(s)
- Vanessa M. Puñal
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Caitlin E. Paisley
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Federica S. Brecha
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Monica A. Lee
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Robin M. Perelli
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Jingjing Wang
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Emily G. O’Koren
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Department of Immunology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Caroline R. Ackley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Department of Cellular, Molecular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Daniel R. Saban
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Department of Immunology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Benjamin E. Reese
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Jeremy N. Kay
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
9
|
Ghinia MG, Novelli E, Sajgo S, Badea TC, Strettoi E. Brn3a and Brn3b knockout mice display unvaried retinal fine structure despite major morphological and numerical alterations of ganglion cells. J Comp Neurol 2019; 527:187-211. [PMID: 27391320 PMCID: PMC5219957 DOI: 10.1002/cne.24072] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 06/07/2016] [Accepted: 06/30/2016] [Indexed: 01/21/2023]
Abstract
Ganglion cells (GCs), the retinal output neurons, receive synaptic inputs from bipolar and amacrine cells in the inner plexiform layer (IPL) and send information to the brain nuclei via the optic nerve. Although GCs constitute less than 1% of the total retinal cells, they occur in numerous types and are the first neurons formed during retinal development. Using Brn3a and Brn3b mutant mice in which the alkaline phosphatase gene was knocked-in (Badea et al. [Neuron] 2009;61:852-864; Badea and Nathans [Vision Res] 2011;51:269-279), we studied the general effects after gene removal on the retinal neuropil together with the consequences of lack of development of large numbers of GCs onto the remaining retinal neurons of the same class. We analyzed the morphology, number, and general architecture of various neuronal types presynaptic to GCs, searching for changes secondary to the decrement in the number of their postsynaptic partners, as well as the morphology and distribution of retinal astrocytes, for their strong topographical relation to GCs. We found that, despite GC losses, retinal organization in Brn3 null mice is remarkably similar to that of wild-type controls. J. Comp. Neurol. 527:187-211, 2019. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Miruna Georgiana Ghinia
- Neuroscience Institute of the Italian National Research Council, Pisa Research Campus, 56124 Pisa, Italy
- Retinal CIrcuit Development & Genetics Unit, Neurobiology–Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
- Babeş Bolyai University, 400084 Cluj Napoca, Romania
| | - Elena Novelli
- Neuroscience Institute of the Italian National Research Council, Pisa Research Campus, 56124 Pisa, Italy
| | - Szilard Sajgo
- Retinal CIrcuit Development & Genetics Unit, Neurobiology–Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Tudor Constantin Badea
- Retinal CIrcuit Development & Genetics Unit, Neurobiology–Neurodegeneration and Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892
| | - Enrica Strettoi
- Neuroscience Institute of the Italian National Research Council, Pisa Research Campus, 56124 Pisa, Italy
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Abstract
Retinal bipolar cells spread their dendritic arbors to tile the retinal surface, extending them to the tips of the dendritic fields of their homotypic neighbors, minimizing dendritic overlap. Such uniform nonredundant dendritic coverage of these populations would suggest a degree of spatial order in the properties of their somal distributions, yet few studies have examined the patterning in retinal bipolar cell mosaics. The present study examined the organization of two types of cone bipolar cells in the mouse retina, the Type 2 cells and the Type 4 cells, and compared their spatial statistical properties with those of the horizontal cells and the cholinergic amacrine cells, as well as to random simulations of cells matched in density and constrained by soma size. The Delauney tessellation of each field was computed, from which nearest neighbor distances and Voronoi domain areas were extracted, permitting a calculation of their respective regularity indexes (RIs). The spatial autocorrelation of the field was also computed, from which the effective radius and packing factor (PF) were determined. Both cone bipolar cell types were found to be less regular and less efficiently packed than either the horizontal cells or cholinergic amacrine cells. Furthermore, while the latter two cell types had RIs and PFs in excess of those for their matched random simulations, the two types of cone bipolar cells had spatial statistical properties comparable to random distributions. An analysis of single labeled cone bipolar cells revealed dendritic arbors frequently skewed to one side of the soma, as would be expected from a randomly distributed population of cells with dendrites that tile. Taken together, these results suggest that, unlike the horizontal cells or cholinergic amacrine cells which minimize proximity to one another, cone bipolar cell types are constrained only by their physical size.
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|