Subcellular localization of Dp71 dystrophin isoforms in cultured hippocampal neurons and forebrain astrocytes

It has been suggested that the absence or altered structure of Dp71, a C-terminal dystrophin gene encoded protein, is responsible for mental alterations observed in about 30% of Duchenne muscular dystrophy patients. Most of these patients have premature translational termination or point mutations at the C-terminal domain of this gene. In brain, Dp71 is the major protein product of the dystrophin gene. To determine the function of Dp71 isoforms in this organ, it is important to document their presence and intracellular localization in brain cells. Extracts from cultured hippocampal neurons and forebrain astrocytes and 5F3 and Dys 2 monoclonal antibodies were thus used for western blots. In these conditions, two Dp71 isoforms spliced or not at exon 78 were detected in both cells (Dp71f and Dp71d, respectively). By immunocytochemistry, we mapped Dp71f and Dp71d in the Golgi complex (GC) and in neuronal nuclei. Only Dp71d was found in cytoplasmic neurofilaments. In astrocytes, these isoforms were detected in the GC. These cell localization data suggest that these Dp71 isoforms may have different functions in the same cell or organelle, as well as in the two different cells analyzed.