P.327In-depth characterisation of brain pathology in mice lacking one or multiple brain dystrophin isoforms

Abstract

Duchenne muscular dystrophy (DMD) is a lethal muscle-wasting disorder caused by lack of dystrophin. Several dystrophin isoforms are also expressed in the brain, and its absence there underlies behavioural issues, learning difficulties and intellectual impairments observed frequently in patients. Severity of brain-related pathology seems to correlate with the number of brain dystrophin isoforms lacking. Absence of the most commonly deleted brain isoforms (Dp427+Dp140) results in more severe behavioural and anatomical impairments compared to those seen in patients lacking only Dp427. As cognitive problems limit social participation, elucidating brain pathology is vital. Here animal studies are instrumental as they allow both in vivo and post-mortem studies. Like DMD patients, also mdx mice (lacking Dp427) suffer from behavioural impairments and brain pathology. Mice lacking Dp427+Dp140 (mdx4cv) are available, however, their behaviour and brain pathology have never been characterized in detail. We thoroughly investigated the roles of Dp427 and Dp140 in these DMD models. To elucidate how dystrophinopathy impacts behaviour, n=20 mdx, mdx4cv and wildtype males were housed in automated home-cages equipped with pellet-dispensers where spontaneous behaviour, appetitive conditioning, cognitive flexibility and anxiety was assessed. In addition, mice were subjected to T-maze and Morris water maze experiments in which spatial learning and cognitive flexibility was studied. In all assessments, the wild type mice outperformed the mdx and mdx4c mice. Mdx and mdx4cv mice were equally affected for e.g. cognitive flexibility in water maze and alterations in T-maze. Brain pathology was studied by MRI using the contrast solutions gadoteridol or manganese (n=10 per group). We assessed anatomical changes of individual brain areas, white matter integrity, blood-brain-barrier integrity and calcium channel activation. Thereafter, either whole brains or individual brain areas were isolated to study pathophysiology in detail via histological and gene expression analyses respectively. MRI scans have been completed, and their analyses and the post-mortem studies are ongoing, but will be completed prior to the congress. This data will increase our understanding of the role of dystrophin in the brain, which will facilitate the development of therapies to treat the Duchenne brain pathology.