When human eyes look at their environment they collect pictures that are sent to the brain. Together these pictures form a visual representation of our world. The eyes transmit visual images to the brain through a cable that is composed of nerve fibres called retinal axons. The retinal axons connect the eye to visual areas of the brain, including the optic tectum (OT).
Unfortunately, retinal axons can degenerate in conditions like glaucoma, eventually leading to irreversible blindness. Currently, it is unknown how developing retinal axons connect with the brain, which has limited the creation of new therapies.
Recent findings from TWRI Senior Scientist Dr. Philippe Monnier have addressed this problem by shedding light on how retinal axons are guided during development. The researchers found that a group of peptides, known as Repulsive Guidance Molecule a (RGMa) subtypes, work in combination to help retinal axons target the OT. One of the subtypes, C-RGMa, inhibits deep projections in the optic tectum, while the other, N-RGMa, promotes deeper projections in the OT. A balance of both peptides ensures that retinal axons connect with the appropriate area of the OT.
Remarks Dr. Monnier, "Our work has uncovered the peptides responsible for ensuring that retinal axons integrate into the correct layer of the OT. These insights may help developing therapies aimed at restoring vision in patients with retinal axon damage."
This work was supported by the Canadian Institutes of Health Research, the Vision Science Research Program of the University of Toronto and the Toronto General & Western Hospital Foundation.
Ƴ-secretase and LARG mediate distinct RGMa activities to control appropriate layer targeting within the optic tectum. Banerjee P, Harada H, Tassew NG, Charish J, Goldschneider D, Wallace VA, Sugita S, Mehlen P, Monnier PP . Cell Death and Differentiation. 2015 Aug 21. [Pubmed abstract]