Tumor necrosis factor-alpha is produced by dying retinal neurons and is required for Muller glia proliferation during zebrafish retinal regeneration

• Published in: The Journal of neuroscience Vol. 33; no. 15; pp. 6524 - 6539
• Main Authors: Nelson, Craig M, Ackerman, Kristin M, O'Hayer, Patrick, Bailey, Travis J, Gorsuch, Ryne A, Hyde, David R
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 10.04.2013
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - physiology; Basic Helix-Loop-Helix Transcription Factors - biosynthesis; Cell Proliferation - drug effects; Gene Expression - physiology; Gene Knockdown Techniques - methods; Heparin-binding EGF-like Growth Factor; Intercellular Signaling Peptides and Proteins - biosynthesis; Intercellular Signaling Peptides and Proteins - pharmacology; Light - adverse effects; Nerve Regeneration - drug effects; Nerve Regeneration - physiology; Neuroglia - physiology; Ouabain - pharmacology; Photoreceptor Cells - metabolism; Photoreceptor Cells - physiology; Photoreceptor Cells, Vertebrate - physiology; Retinal Neurons - drug effects; Retinal Neurons - metabolism; Retinal Neurons - physiology; STAT3 Transcription Factor - biosynthesis; Tumor Necrosis Factor-alpha - biosynthesis; Tumor Necrosis Factor-alpha - physiology; Zebrafish; Zebrafish Proteins - biosynthesis; Zebrafish Proteins - metabolism; Zebrafish Proteins - physiology
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.3838-12.2013

Intense light exposure causes photoreceptor apoptosis in dark-adapted adult albino zebrafish (Danio rerio). Subsequently, Müller glia increase expression of the Achaete-scute complex-like 1a (Ascl1a) and Signal transducer and activator of transcription 3 (Stat3) transcription factors and re-enter the cell cycle to yield undifferentiated neuronal progenitors that continue to proliferate, migrate to the outer nuclear layer, and differentiate into photoreceptors. A proteomic analysis of light-damaged retinal homogenates, which induced Müller glia proliferation when injected into an undamaged eye, revealed increased expression of tumor necrosis factor α (TNFα) signaling proteins relative to undamaged retinal homogenates. TNFα expression initially increased in apoptotic photoreceptors and later in Müller glia. Morpholino-mediated knockdown of TNFα expression before light damage diminished the expression of both Ascl1a and Stat3 in Müller glia and significantly reduced the number of proliferating Müller glia without affecting photoreceptor cell death. Knockdown of TNFα expression in the Müller glia resulted in fewer proliferating Müller glia, suggesting that Müller glial-derived TNFα recruited additional Müller glia to re-enter the cell cycle. While TNFα is required for increased Ascl1a and Stat3 expression, Ascl1a and Stat3 are both necessary for TNFα expression in Müller glia. Apoptotic inner retinal neurons, resulting from intravitreal injection of ouabain, also exhibited increased TNFα expression that was required for Müller glia proliferation. Thus, TNFα is the first molecule identified that is produced by dying retinal neurons and is necessary to induce Müller glia to proliferate in the zebrafish retinal regeneration response.