ARF1 and Intellectual disability: Levels of ARF1 activity may be important to examine further since complete loss of function is embryonic lethal.31 The 1q42 genomic region, where ARF1 resides, has also been implicated in brain development and white matter abnormalities, and our studies add ARF1 to the candidates that could influence the brain.32 Future attention to ARF1 and other GTPases could assist in our understanding neuronal pathogenesis and other intellectual disabilities.