Muller glia

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.^[1] 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.^[2]

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.^[3] Müller glia have also been implicated to serve as guidepost cells for the developing axons of neurons in the chick retina.^[4] Studies using a zebrafish model of Usher syndrome have implicated a role for Müller glia in synaptogenesis, the formation of synapses.^[5]

Neuronal support

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.^[6] Müller glia have also been shown to be important in the induction of glutamine synthetase in chicken embryos,^[7] which is a process important in the regulation of glutamine activity 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.^[8]

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.^[9] Studies to this end of Müller glia in both the zebrafish^[10] and chicken^[11] 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.^[12] Studies in human models have demonstrated that Müller glia have the potential to serve as stem cells in the adult retina^[13] and are efficient rod photoreceptor progenitors.^[14]

See also

• Radial glia

References

External links

• New Hope For Regenerating Damaged Human Retina: Sleeping Stem Cells Successfully Awakened
• Müller cells at Virginia-Maryland Regional College of Veterinary Medicine
• Reichenbach A, Faude F, Enzmann V et al. (1997). "The Müller (glial) cell in normal and diseased retina: a case for single-cell electrophysiology". Ophthalmic Res. 29 (5): 326–40. doi:10.1159/000268031. PMID 9323724. 
• NIF Search - Muller Cell via the Neuroscience Information Framework

v t e Sensory system – visual system – globe of eye (TA A15.2.1–6, TH 3.11.08.0-5, GA 10.1005) Fibrous tunic (outer) Sclera Episcleral layer • Schlemm's canal • Trabecular meshwork Cornea Limbus • layers (Epithelium, Bowman's, Stroma, Descemet's, Endothelium) Uvea/vascular tunic (middle) Choroid Capillary lamina of choroid • Bruch's membrane • Sattler's layer Ciliary body Ciliary processes • Ciliary muscle Iris Stroma • Pupil • Iris dilator muscle • Iris sphincter muscle Retina (inner) Layers Inner limiting membrane • Nerve fiber layer • Ganglion cell layer • Inner plexiform layer • Inner nuclear layer Outer plexiform layer • Outer nuclear layer External limiting membrane • Layer of rods and cones • Retinal pigment epithelium Cells Photoreceptor cells (Cone cell, Rod cell) → (Horizontal cell) → Bipolar cell → (Amacrine cell) → Retina ganglion cell (Midget cell, Parasol cell, Bistratified cell, Giant retina ganglion cells, Photosensitive ganglion cell) → Diencephalon: P cell, M cell, K cell Muller glia Other Macula (Foveola, Fovea centralis) • Optic disc (Optic cup) Anterior segment Anterior chamber • Aqueous humour • Posterior chamber • Lens (Capsule of lens, Zonule of Zinn) Posterior segment Vitreous humour Other Ocular immune system • Tapetum lucidum • Keratocytes M: EYE anat(g/a/p)/phys/devp/prot noco/cong/tumr, epon proc, drug(S1A/1E/1F/1L)