Müller glia

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Müller glia are glial cells present in the retinas of vertebrates.

Müller glia

A comparison between the structure of a fibre optic plate (left) and the structure of Müller glia in the retina. Source: vision-research.eu

Müller glia, or Müller cells are glial cells present in the vertebrate retina. These radial glial cells perform several functions. Firstly, they act as standard glial cells in providing structural support and nourishment for surrounding cells. Müller glia are also capable of undergoing de-differentiation, becoming retinal stem cells, which can divide and differentiate into multiple types of retinal cell, proliferating after injury to the retina. It has also been shown that the Mûller glia can act as a sort of optical fiber, collecting light and carrying it toward photoreceptor cells in the retina.

Cell Type: Radial Glia

Anatomy

Müller cells are roughly 150μm in length and cover the width of the retina. The cells have a cylindrical, fiber-like shape. Müller glia extend from the vitreous humour to the photoreceptor cells within the retina and possess a distinctive funnel-like structure (“endfeet”) of roughly 12-15μm in diameter which form a cobble-stone type pattern on the membrane most near to the vitreous humour. Müller glia are oriented along the path through which light travels, with light first encountering the “endfeet” and then traveling down the length of the cell.

Properties

The distinctive funnel-like “endfeet” cover the inner retinal surface and have a low refractive index; this allows light to easily pass through. Each muller cell is generally couple with a single cone photoreceptor cell, but the number of rods varies somewhat widely from species to species (roughly ten in humans). Muller cells have the optical property of acting as low-scattering conduits through which light can easily pass; they possess few organelles such as mitochondria which could cause light-scattering, and are largely composed of long, thin, filaments. The funnel-like shape of the Muller glia leaves allows the passage of light while preserving a substantial amount of retinal space for other cells and their neuronal connections.


References

  1. Franze, K., et al (2007). Müller cells are living optical fibers in the vertebrate retina. Proc. Nat. Acad. Sci. 104: 8287-8292. DOI: 10.1073/pnas.0611180104
  1. Bernardos RL, Barthel LK, Meyers JR, Raymond PA. Late-stage neuronal progenitors in the retina are radial Müller glia that function as retinal stem cells. J Neurosci. 2007 Jun 27;27(26):7028-40.
  1. Deepak A. Lambaa, Mike O. Karla and Thomas A. Reh, Strategies for retinal repair: cell replacement and regeneration . Progress in Brain Research

Volume 175, 2009, Pages 23-31 doi:10.1016/S0079-6123(09)17502-7

  1. http://education.vetmed.vt.edu/curriculum/vm8054/EYE/MULLER.HTM