Abstract

Several studies have indicated that apoptotic pathways are responsible for the loss of motor neurons that constitutes the hallmark of adult-onset neurodegenerative disease amyotrophic lateral sclerosis (ALS). In this study we demonstrate that motoneuronal death induced by the expression of mutant Cu,Zn superoxide dismutase (SOD1) typical of familial ALS is mediated by Bcl2a1, a protein belonging to the Bcl2 family. Bcl2a1 is the only member of this family to be up-regulated selectively in spinal motor neurons of mice transgenic for G93A-SOD1 already at the asymptomatic stage. Bcl2a1 over-expression is restricted to motor neurons, it is not depending on the genetic background of mice and it is not due to a general activation of NF-_kB-regulated genes. Over-expression of Bcl2a1 is protective against death of neuronal cells induced by expression of G93A-SOD1 but is detrimental upon stimulation of those cells with tumor necrosis factor. Since this factor is known to contribute to the complex molecular cross-talk among different cell types taking place in the pathogenesis of ALS, we propose that the increase in Bcl2a1 is a triggering event in the progressive loss of motor neurons occurring in this disease.

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