IGF1 and amyotrophic lateral sclerosis: Overexpression of either IGF-1 or IGF-2 in susceptible motor neurons, using adeno-associated virus, protect these from degeneration in ALS mouse models and prolonged lifespan, while inducing peripheral nerve sprouting and formation of new NMJs.4 IGF-2 was also shown to protect human stem cell-derived motor neurons across ALS-like conditions (Fig. 2C).