P.310Validating the use of deltaE50-MD dogs for modelling the cognitive, psychological and brain phenotype of Duchenne muscular dystrophy

Abstract

Approximately 50% of patients with Duchenne Muscular Dystrophy (DMD) have neuropsychiatric disorders (including anxiety, intellectual impairment, autism spectrum disorder) associated with dystrophin deficiency in the brain. Brain dystrophin expression is ∼10% of that in muscle, yet the brain expresses a wider variety of dystrophin isoforms (Dp427, Dp140 and Dp71). The expression pattern and functional roles of these isoforms in the brain have not been fully elucidated, and many studies have relied on the use of mice, in which detailed assessment of brain function is challenging and often not directly translatable to humans. Currently lacking is a well-defined animal model of the functional brain deficits of DMD.The aim of this project is to validate the use of deltaE50-MD dogs as a model of the cognitive impairment of DMD. These dogs carry a deletion of exon 50 of the dystrophin gene (at the centre of the human DMD mutation hotspot) and are predicted to have a deficit in Dp140, believed to be crucial in normal brain function. First, using qRT-PCR, RNAScope and immunostaining we are investigating expression of dystrophin isoforms in normal dog and deltaE50-MD dog brains. RNAScope in situ hybridisation reveals the normal canine sub-cellular brain localisation of specific dystrophin transcripts in selected regions. Second, to quantify the extent to which deltaE50-MD dogs have a detectable brain disorder, a battery of tests are being developed to assess cognitive function. Our data show that, compared to litter mate controls, affected dogs appear to have reduced attentiveness and motivation, reduced exploration of novel objects and more anxiety-like behaviour. By validating the use of the deltaE50-MD dog model, we aim in future to test novel therapies designed to restore brain dystrophin expression, prior to translation to human trials. Success in this field would be transformative for DMD patients for whom the brain comorbidities can be profoundly debilitating.