A comparison between the transcriptome of the brain in patients with narcolepsy and that of a healthy human brain, as well as a comparison of mutant mice devoid of HCRT neurons with wild-type mice, showed that the IGFBP3 protein is colocalized in about 80% of HCRT neurons in mice and only 10–20% of HCRT neurons in humans [45]. This evidence concerns the gene HCRT and narcolepsy.