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Published on: November 2, 2015
Growth hormone-induced neuroprotection in the neural retina during chick embryogenesis
Steve Harvey1, Marie-Laure Baudet, Esmond J Sanders
1Department of Physiology, University of Alberta, Edmonton, Alberta, Canada. steve.harvey@ualberta.ca
Insights
Growth hormone (GH) is produced in chick embryo retinas before the pituitary develops, aiding axonal growth and protecting retinal ganglion cells (RGCs) from cell death.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- Retinal ganglion cells (RGCs) are identified as extrapituitary sites for growth hormone (GH) production and function in early chick embryos.
- This occurs before the development of pituitary somatotrophs, suggesting a critical early role for GH in the visual system.
Purpose of the Study:
- To investigate the role of GH in the developing visual system of chick embryos.
- To explore the functions of GH in RGCs, including axonal guidance and neuroprotection.
Main Methods:
- The study focuses on the presence and localization of GH within RGCs and their axons during embryogenesis.
- Analysis of GH signaling pathways involved in neuroprotection during RGC differentiation and apoptosis.
Main Results:
- GH is present in RGC axons during the projection phase to brain visual centers, indicating a role in axonal growth or guidance.
- Retinal GH exhibits neuroprotective effects against developmental apoptosis in RGCs.
- The anti-apoptotic mechanisms of retinal GH involve signaling pathways similar to known neurotrophins like BDNF and IGF-1.
Conclusions:
- Growth hormone acts as a novel neurotrophin within the developing chick visual system.
- Retinal GH plays crucial roles in both the development and survival of retinal ganglion cells during embryogenesis.
Abstract:
Recent studies have established that retinal ganglion cells (RGCs) of the neural retina are extrapituitary sites of growth hormone (GH) production and action in early chick embryos prior to the ontogeny of pituitary somatotrophs. The presence of GH in axons of the RGCs is, however, restricted to the period when the retinofugal neurons project to and synapse with visual centers within the brain, suggesting roles for GH in axonal growth or guidance. Autocrine and/or paracrine actions of retinal GH are also neuroprotective for RGCs during developmental waves of apoptosis that characterize RGC differentiation. The anti-apoptotic actions of retinal GH use signaling mechanisms that are common to other established neurotrophins (e.g., brain-derived growth factor, insulin-like growth factor-1, transforming growth factor beta-1). Retinal GH is therefore a novel neurotrophin in the visual system during chick embryogenesis.
