Dystrophin (Dp427) expression and regulation in human and mouse neuronal cells : in vitro studies

Duchenne muscular dystrophy (DMD) is a common X-linked recessive neuromuscular disease due to altered dystrophin, a cytoskeletal protein of 427 KDa (Dp427) expressed not only in muscles, but also in several brain areas and autonomic neurons. Cognitive and behavioral impairment in DMD patients suggest a specific actions of Dp427 in the nervous system. The aim of the study was to investigate the expression and functions of Dp427 in neurons using human neuroblastoma cell lines and mouse immortalized hypothalamic neurons (GT1-7 and GN11) in vitro. We found that several neuroblastoma cell lines express measurable levels of Dp427. Moreover, SK-N-BE cells induced to differentiate into more neuronal-like phenotype, by exposure to retinoic acid (RA, 10 uM), showed a strong decrease of Dp427 transcript and protein, but not of the shorter Dp71. RA induced an unexpected increase of the beta-distroglican, a component of the dystrophin-protein-complex (DPC). We also found that Dp427 was expressed in GT1-7 neurons but not in immature GN11 cells. Transfection with a 3849 bp minidystrophin–EGFP fusion protein induced evident changes in both morphology (expansion of filopodia and lamellipodia) and intracellular actin distribution of GN11 cells. Conclusions: a) RA may exert a specific regulation on Dp427 expression in human neuronal-like cells; b) the hyperexpression of mindystrophin may induce strong morphological modification of immortalized central neurons.