The rod signaling pathway in marsupial retinae

  • The retinal rod pathway, featuring dedicated rod bipolar cells (RBCs) and AII amacrine cells, has been intensely studied in placental mammals. Here, we analyzed the rod pathway in a nocturnal marsupial, the South American opossum Monodelphis domestica to elucidate whether marsupials have a similar rod pathway. The retina was dominated by rods with densities of 338,000–413,000/mm². Immunohistochemistry for the RBC-specific marker protein kinase Cα (PKCα) and the AII cell marker calretinin revealed the presence of both cell types with their typical morphology. This is the first demonstration of RBCs in a marsupial and of the integration of RBCs and AII cells in the rod signaling pathway. Electron microscopy showed invaginating synaptic contacts of the PKCα-immunoreactive bipolar cells with rods; light microscopic co-immunolabeling for the synaptic ribbon marker CtBP2 confirmed dominant rod contacts. The RBC axon terminals were mostly located in the innermost stratum S5 of the inner plexiform layer (IPL), but had additional side branches and synaptic varicosities in strata S3 and S4, with S3-S5 belonging to the presumed functional ON sublayer of the IPL, as shown by immunolabeling for the ON bipolar cell marker Gγ13. Triple-immunolabeling for PKCα, calretinin and CtBP2 demonstrated RBC synapses onto AII cells. These features conform to the pattern seen in placental mammals, indicating a basically similar rod pathway in M. domestica. The density range of RBCs was 9,900–16,600/mm2, that of AII cells was 1,500–3,260/mm2. The numerical convergence (density ratio) of 146–156 rods to 4.7–6.0 RBCs to 1 AII cell is within the broad range found among placental mammals. For comparison, we collected data for the Australian nocturnal dunnart Sminthopsis crassicaudata, and found it to be similar to M. domestica, with rod-contacting PKCα-immunoreactive bipolar cells that had axon terminals also stratifying in IPL strata S3-S5.

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Author:Nicolas Lutz, Emina Lemes, Leah Krubitzer, Shaun Colli, Silke Haverkamp, Leo Peichl
Pubmed Id:
Parent Title (English):PLoS one
Place of publication:Lawrence, Kan.
Contributor(s):Steven Barnes
Document Type:Article
Year of Completion:2018
Date of first Publication:2018/08/29
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2018/08/30
Tag:Axons; Domestic animals; Eutheria; Marsupials; Opossums; Photoreceptors; Retina; Synapses
Issue:(8): e0202089
Page Number:19
First Page:1
Last Page:19
Copyright: © 2018 Lutz et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Institutes:Biowissenschaften / Biowissenschaften
Angeschlossene und kooperierende Institutionen / MPI für Hirnforschung
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Licence (German):License LogoCreative Commons - Namensnennung 4.0