The large DMD gene encodes a group of dystrophin proteins in brain and retina, produced from multiple promoters and alternative splicing events. Dystrophins are core components of different scaffolding complexes in distinct cell types. Their absence may thus alter several cellular pathways, which might explain the heterogeneous genotype–phenotype relationships underlying central comorbidities in Duchenne muscular dystrophy (DMD). However, the cell-specific expression of dystrophins and associated proteins (DAPs) is still largely unknown. The present study provides a first RNA-Seq-based reference showing tissue- and cell-specific differential expression of dystrophins, splice variants and DAPs in mouse brain and retina. We report that a cell type may express several dystrophin complexes, perhaps due to expression in separate cell subdomains and/or subpopulations, some of which with differential expression at different maturation stages. We also identified new splicing events in addition to the common exon-skipping events. These include a new exon within intron 51 (E51b) in frame with the flanking exons in retina, as well as inclusions of intronic sequences with stop codons leading to the presence of transcripts with elongated exons 40 and/or 41 (E40e, E41e) in both retina and brain. PCR validations revealed that the new exons may affect several dystrophins. Moreover, immunoblot experiments using a combination of specific antibodies and dystrophin-deficient mice unveiled that the transcripts with stop codons are translated into truncated proteins lacking their C-terminus, which we called N-Dp427 and N-Dp260. This study thus uncovers a range of new findings underlying the complex neurobiology of DMD.

Dystrophin-Dp71 being a key membrane cytoskeletal protein, expressed mainly in Müller cells that provides a mechanical link at the Müller cell membrane by direct binding to actin and a transmembrane protein complex. Its absence has been related to blood-retinal barrier permeability through delocalization and down-regulation of the AQP4 and Kir4.1 channels (1). We have previously shown that the adeno-associated virus variant, ShH10, transduces Müller cells in the Dp71-null mouse retina efficiently and specifically (2, 3). Here, we use ShH10 to restore Dp71 expression in Müller cells of Dp71 deficient mouse to study molecular and functional effects of this restoration in an adult mouse displaying retinal permeability. We show that strong and specific expression of exogenous Dp71 in Müller cells leads to correct localization of Dp71 protein restoring all protein interactions in order to re-establish a proper functional blood-retinal barrier and retina homeostasis thus preventing retina from edema. This study is the basis for development of new therapeutic strategies in dealing with diseases with blood-retinal barrier breakdown and macular edema such as diabetic retinopathy.

J. Neurochem. (2011) 119, 697–707. Dp71 has an important role in the central nervous system. To better understand the function of Dp71 domains in neuronal differentiation, PC12 cells were stably transfected with a dystrophin mutant, Dp71Δ_78‐79, which lacks exons 78 and 79. Based on the percentage of cells bearing neurites and neurite length analyses, we found that cells stably expressing Dp71Δ_78‐79 (PC12‐C11) differentiate more efficiently than non‐transfected cells. While wild‐type cells reach their maximum differentiation 9–12 days after initiating the differentiation process, the PC12‐C11 cells reach differentiation in 4–6 days. Protein expression analysis showed a down‐regulation of Dp71a and an up‐regulation of Dp71ab and/or Up71, β‐dystroglycan and neuron‐specific enolase in undifferentiated and in neural growth factor differentiated PC12‐C11 cells. No change was observed in the expression of Grb2 and Up400. The subcellular localization of Dp71Δ_78‐79 was in the cell periphery, and there was no change in localization during the differentiation process, which was also observed throughout the neurite extensions.