We therefore decided to study the genetic variability of the melatonin receptor MTNR1A and MTNR1B genes and the GPR50 gene in autism spectrum disorder (ASD) patients, in parallel to a normal European control population as well as in individuals of the human genome pluriethnic diversity panel (HGDP), by direct sequencing of the coding regions. The gene discussed is MTNR1A; the disease is autism spectrum disorder.