Why do some diseases affect only specific organs, leaving others invulnerable? Researchers have found neural tissue contains imbalanced levels of proteins, which may explain the brain's susceptibility to a debilitating childhood movement disorder. Compared to nonneuronal cells, neurons have dramatically lower levels of torsinB, a sister protein that can work similarly to torsinA. When the DYT1 gene mutation causes a defect in torsinA, torsinB can take over its role in all other cells except for neuronal cells.