Lack of changes in the PI3K/AKT survival pathway in the spinal cord motor neurons of a mouse model of familial amyotrophic lateral sclerosis.

The vulnerability of motor neurons in transgenic SOD1G93A mice, a model of familial amyotrophic lateral sclerosis (ALS), may depend on the failure of these cells to activate survival mechanisms in response to the toxic mutant SOD1. To test this we investigated whether defects in the PI3K/Akt pathway, a survival signal, and of its neuron-specific activator, Rai, were important for motor neuron degeneration in these mice. No substantial changes were found in the levels of Rai, PI3K(p85) or phosphorylated Akt (P-Akt) in the ventral horn of spinal cord of SOD1G93A mice during disease progression. P-Akt immunoreactivity was the same in degenerating and healthy motor neurons. Rai ablation in SOD1G93A mice slightly accelerated the motor dysfunction without affecting their life span. Thus, motor neurons in SOD1G93A mice do not lose the pro-survival PI3K/Akt signal nor increase it in order to suppress the cell death mechanisms.