The major aim of our proposal is to generate zebrafish models of a human eye movement disorder, to replace mouse models. Eye movement disorders affect 1% of the human population. In severe cases, such disorders can result in amblyopia and partial blindness, and there is currently no effective treatment. Duane Retraction Syndrome (DRS) is a congenital form of squint in which horizontal eye movements are defective. Patients with DRS have abnormal wiring of the ocular motor system - the nerves and muscles that control eye movements. We previously showed that DRS can result from mutations in the cytoplasmic signalling molecule alpha2-chimaerin, and demonstrated that transient manipulations of alpha2-chimaerin signalling in the chick and zebrafish model systems leads to defects in ocular motor wiring, akin to DRS in humans. In this proposal, we will make more permanent models of DRS, to act as a resource for the research community. We will generate stable transgenic zebrafish lines with loss- or gain-of-function of alpha2-chimaerin, in order to determine the effects of chimaerin signalling levels and to model DRS. Gain-of-function models will either over-express the wild-type alpha2-chimaerin protein, or will harbour human alpha2-chimaerin mutations. We will map the neuroanatomy of the ocular motor system in these lines, and functionally test the optokinetic reflex to determine the impairment of eye movements. These data will be directly compared with neuroimaging and functional data in humans, to gain insight into the causation of DRS. Our zebrafish models will be disseminated to the research community, as a replacement and a desirable alternative to the mouse. All experimental analysis will be carried out on larvae at 1-5 days post-fertilisation, and therefore not 'protected' species. Neuroanatomical studies will involve live and time-lapse imaging allowing quantitation of multiple parameters from a single animal, thus allowing a reduction of animal usage.