Sussex Neuroscience

Professor Sarah Guthrie

Sarah GuthrieUnderstanding alpha2-chimaerin signalling in the normal and abnormal development of the ocular motor system

PROJECT SUMMARY

Eye movements in humans depend on a system of nerves and muscles which rotate the eyeball – the ocular motor system. The correct function of this system depends on the precise navigation of nerves during development; incorrect development leads to eye movement disorders such as squint. Mutations in the signalling molecule alpha2-chimaerin (α2-chn) cause squint in humans, and neuroimaging shows that affected individuals manifest miswiring of their cranial nerves. Our studies have shown that α2-chn plays an important role in wiring the ocular motor system, by controlling the cytoskeleton. Manipulation of α2-chn signalling in chick or zebrafish in vivo leads to axon guidance defects and faulty connectivity of nerves to the extraocular muscles.

There is still little information about which signalling pathways are activated by α2-chn to control axon guidance. This project will explore the signalling networks regulated by alpha2-chimaerin to unravel the mechanisms that use squint in humans. We have recently used a proteomics screen to identify potential α2-chn-interacting partners. This project will investigate one or more of these candidate proteins to test whether they are part of the α2-chn signalling network. Techniques used will include molecular biology, microinjection, transgenic breeding, imaging and phenotypic analysis in the zebrafish, behavioural assays, and neuronal cell culture. The specific aims of the project will be a) to evaluate binding of candidate molecules to α2-chn using biochemical approaches b) to evaluate whether gain or loss of function of these molecules leads to axon wiring defects in the zebrafish embryo c) to evaluate whether gain or loss of function of candidate molecules leads to defects in behaviour (the optokinetic reflex).

The initial rotation project will test the effect of manipulating expression of a candidate molecule, CRMP2, in the zebrafish embryo, and evaluate phenotypes using 2-photon microscopy and image analysis.

REFERENCES

Clark, C., Austen, O., Poparic, I. and Guthrie, S. (2013). Alpha2-chimaerin regulates a key axon guidance transition during development of the oculomotor projection. J. Neurosci. 33, 16540-16551.

Miyake, N. et al.(2008). Human CHN1 mutations hyperactivate α2-chimaerin and result in ocular motor dysfunction. Science 321, 839-843.