During neurological development, Arf6 is highly expressed in the human brain and Arf6 dysfunction leads to defects in the cellular migration that contribute to neuronal disease.253 Defective Arf-related processes are involved in autosomal recessive periventricular heterotopia, retinitis pigmentosa, and amyotrophic lateral sclerosis as a consequence of defective neuron migrations. This evidence concerns the gene ARF6 and nodular neuronal heterotopia.