Due to a mutation in the survival motor neuron gene 1 (SMN1), individuals with spinal muscular atrophy (SMA) don’t produce survival motor neuron (SMN) protein at high enough levels. Without this protein, the motor neuron cells shrink and eventually die. This causes debilitating and potentially fatal muscle weakness.
One way of treating SMA is to increase the amount of survival motor neuron protein in the body. These ways of treating SMA are often called “SMN-based” or “SMN-enhancing” approaches.
All individuals with SMA have at least one, and often multiple, copies of a second gene, called survival motor neuron gene 2 (SMN2), or the “SMA back-up gene.” SMN2 also produces SMN protein, but only a small percentage of the protein produced by SMN2can be used by the body.
Many SMN-enhancing treatments target this SMN2 gene, causing it to make more useable SMN protein. Other SMN-enhancing approaches work to replace or repair the mutatedSMN1gene directly.