WP2 determined expression of dystrophin isoforms at a cellular level using RNA hybridisation techniques, in human and mouse brain. The structure/function relationship was established and is relevant for clinical findings. The identification of cells co-expressing dystrophin isoforms in different combinations, highlighted an unexpected heterogeneity. Dp140 isoform was linked to glutamergic transmission suggesting the loss downregulates cell-cell interactions between neurons, pericytes and astrocytes. Characterisation of interacting proteins for each brain dystrophin isoform are currently defining novel, isoform specific, brain dystrophin associated complexes.
WP3 developed mdx mouse behavioural outcome measures capable of capturing specific phenotypic differences. This battery of assessment tools can now represent a benchmark for future genetic restoration therapy. In the mdx mice lacking only Dp427 fear response and anxiety was enhanced, with impaired fear conditioning. The further loss of Dp140 alters social and anxiety-related behaviours and impulsivity. In mice lacking all isoforms significant worsening of emotional reactivity was seen. When comparing the animal model profiles to human, there are parallels for which we have similar clinical observation. In partial contrast to the clinical phenotype, the additional lack of Dp71 induced worsening of emotional reactivity, but did not have an effect on learning, suggesting not all features are recapitulated in the mdx.
WP4 compared multiple delivery techniques and ASO chemistries focused on inducing exon skipping and dystrophin restoration. A comparative analysis allowed selection of the most efficient ASO for inducing dystrophin restoration. The restoration of Dp427 at low levels by inducing exon 51 skipping improved emotionally related deficits. This demonstrates that postnatal Dp427 rescue can be achieved and associated with improved phenotype.
WP5 developed a novel online assessment tool, which reached 263 families during COVID-19 lockdown period with a set of validated instruments capable of assessing neurobehavioural comorbidities. Results indicate that over 18% of DMD boys present significant risk for psychosocial adjustment problems, with a clear dystrophin isoform effect. Results provide indirect evidence on the role of individual isoforms on brain comorbidities and suggest that the full length Dp427 is the main isoform involved. Part 2 focused on patients assessed in clinic after the pandemic with assessment of the full-scale IQ; a subset of these patients also underwent brain MRI. A total of 252 DMD and 62 BMD patients were assessed, exceeding the original recruitment figures of 270 D/BMD individuals. The type and number of social and neurobehavioral difficulties did not appear to be associated with the presence of intellectual disability or with the number of brain dystrophin isoforms affected. This reinforces the role of the deficiency of Dp427 as a risk factor for the neurobehavioural comorbidities.
Analysis of clinical MRI is ongoing and will be completed with further funding obtained specifically for finalising the analysis. The preliminary data indicate significantly reduced brain volume in DMD compared to controls, whereas BMD data did not show any volumetric or perfusion differences. Detailed scans of preclinical MRI failed to identify significant total volumetric differences, or differences related to specific regions of interest. This clearly differs from the findings in the human and MRI analysis was not conducted to assess effect of the genetic therapies.
Data integration (WP7) facilitates the FAIRification of data so that they can be best used internally and in future external collaborations. The FAIRification process allows standardized data management and metadata schemata, based on models and ontologies used by the rare disease community. This was applied to transform the heterogeneous BIND data and metadata, which allowed further exchange, integration and analysis within the consortium and with other external FAIR data sources.
WP5 and WP8 collaborated on a short questionnaire that was distributed worldwide and obtained more than 650 responses. In a subset of ~ 100 patients we were able to cross validate the findings with clinical data. There are discussions integrating this questionnaire in existing international registries to facilitate the identification of individuals at risk of brain comorbidities.
WP8 initiated outreach activities, with the identification of three main areas of work that will continue beyond the BIND consortium: an advisory group focused on protocols for psychopharmacological intervention; a clinical advisory group to interact with regulators regarding future genetic study design; and an advisory group on DMD patient preference study.
