Müller glia, or Müller cells, are glial cells found in the vertebrate retina, which serve as support cells for the neurons of the retina as all glial cells do. However, following injury to the retina, it has been shown in zebrafish that Müller glia undergo dedifferentiation into multipotent progenitor cells. The progenitor cell can then divide and differentiate into a number of retinal cell types, including photoreceptor cells, that may have been damaged during injury. Additionally, further research has shown that Müller glia act as light collectors in the mammalian eye, analogous to the fiber optic plate, funneling light to the rod and cone photoreceptors.
Role in development
Müller glia have been shown to be critical to the development of the retina in mice, serving as promoters of retinal growth and histogenesis via a non-specific esterase mediated mechanism. Müller glia have also been implicated to serve as guidepost cells for the developing axons of neurons in the chick retina. Studies using a zebrafish model of Usher syndrome have implicated a role for Müller glia in synaptogenesis, the formation of synapses.
As glial cells, Müller glia serve a secondary but important role to neurons. As such, Müller glia have been shown to serve as important mediators of neurotransmitter (acetylcholine and GABA specifically) degradation and maintenance of a favorable retinal microenvironment in turtles. Müller glia have also been shown to be important in the induction of the enzyme glutamine synthetase in chicken embryos, which is an important actor in the regulation of glutamine and ammonia concentrations in the central nervous system. Müller glia have been further identified as fundamental to the transmission of light through the vertebrate retina due to their unique funnel shape, orientation within the retina and more favorable physical properties.
Use in research
Müller glia are currently being studied for their role in neural regeneration, a phenomenon that is not known to occur in humans. Studies to this end of Müller glia in both the zebrafish and chicken retina have been performed, with the exact molecular mechanism of regeneration remaining unclear. Further studies performed in mice have shown that Müller glia begin to dedifferentiate and exhibit cell cycle markers, yet do not complete mitosis, which implies there is a block of the regeneration process that is unique to mammals. Studies in human models have demonstrated that Müller glia have the potential to serve as stem cells in the adult retina and are efficient rod photoreceptor progenitors.
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- Müller cells acting as light conductor at The Register, based on Franze et al., Müller cells are living optical fibers in the vertebrate retina, PNAS 104(20):8287–8292, 15 May 2007 | 10.1073/pnas.0611180104
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- WebVision: Regeneration in the Visual System of Adult Mammals
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- New Hope For Regenerating Damaged Human Retina: Sleeping Stem Cells Successfully Awakened
- Müller cells at Virginia-Maryland Regional College of Veterinary Medicine
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- NIF Search - Muller Cell via the Neuroscience Information Framework