C9orf72 and amyotrophic lateral sclerosis: Here we propose a fast and easily applicable method to perform Bayesian model selection on gene expression microarray data collected between multiple conditions, and demonstrate an application of this method to publicly available gene expression microarray data from Amyotrophic Lateral Sclerosis (ALS) cases and controls, investigating the impact of C9orf72 GGGGCC repeat expansions in the underlying regulatory network by comparing patients with and without these mutations.