3D animation of Müller cell processes (red) interconnected with a retinalmicroglia cell (green).
Müller glia, orMüller cells, are a type of retinalglial cells, first recognized and described byHeinrich Müller.[1] They are found in thevertebrateretina, where they serve as support cells for the neurons, as all glial cells do. They are the most common type of glial cell found in the retina. While their cell bodies are located in the inner nuclear layer of the retina, they span across the entire retina.[2]
The major role of the Müller cells is to maintain the structural and functional stability of retinal cells. This includes regulation of the extracellular environment via uptake ofneurotransmitters, removal of debris, regulation of K+ levels, storage ofglycogen, electrical insulation of receptors and other neurons, and mechanical support of the neural retina.
Müller glia are derived developmentally from two distinct populations of cells. The Müller glia cell is the only retinal glial cell that shares a commoncell lineage with retinal neurons. A subset of Müller glia has been shown to originate fromneural crest cells.[3] They are shown to be critical to the development of the retina in mice, serving as promoters of retinal growth andhistogenesis, via a nonspecificesterase-mediated mechanism.[4] Müller glia have also been implicated asguidepost cells for the developingaxons of neurons in the chick retina.[5] Studies using a zebrafish model ofUsher syndrome have implicated a role for Müller glia insynaptogenesis, the formation ofsynapses.[6]
Spatial relationship between Müller cells and microglia
As glial cells, Müller glia serve a secondary but important role toneurons. As such, they have been shown to serve as important mediators ofneurotransmitter (acetylcholine andGABA specifically) degradation and maintenance of a favorable retinal microenvironment in turtles.[7] Müller glia have also been shown to be important in the induction of the enzymeglutamine synthetase in chicken embryos,[8] which is an important actor in the regulation of glutamine and ammonia concentrations in thecentral 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.[9]
Müller glia are currently being studied for their role in neural regeneration, a phenomenon which is not known to occur in humans.[10] Studies of the regenerative properties of Müller glia in both thezebrafish[11][12] and the chicken[13] retina have been performed, with the exact molecular mechanism of regeneration remaining unclear. Further studies performed in mice have shown that overexpression ofAscl1 in Müller glia in conjunction with administration of ahistone deacetylase inhibitor allowed for regeneration of retinal neurons from Müller glia.[14] Studies in human models have demonstrated that Müller glia has the potential to serve asstem cells in the adult retina[15] and are efficient rod photoreceptor progenitors.[16]
^Müller, Heinrich (1851)."Zur Histologie der Netzhaut"(PDF).Zeitschrift für Wissenschaftliche Zoologie.3:234–237. Archived fromthe original(PDF) on 2020-12-29. Retrieved2017-12-07.
^Meller, K.; Tetzlaff, W. (1976). "Scanning electron microscopic studies on the development of the chick retina".Cell and Tissue Research.170 (2):145–159.doi:10.1007/bf00224296.PMID954051.S2CID24845744.
^Fischer, Andy J.; Reh, Thomas A. (2001). "Müller glia are a potential source of neural regeneration in the postnatal chicken retina".Nature Neuroscience.4 (3):247–52.doi:10.1038/85090.PMID11224540.S2CID8732324.
