Spatiotemporal gene expression in ALS Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease that affects nerve cells in the brain and the spinal cord. It has proven difficult to identify the early stages of disease and where it spreads within the body. Maniatis et al. used RNA sequencing to define transcriptomic changes over the course of disease in different regions of the spinal cord of a mouse ALS model and a postmortem human ALS spinal cord. From changes in gene expression, they identified disease-associated pathways and established the key steps in motor neuron degeneration observed in ALS. Science , this issue p. 89