NPTX2 and narcolepsy: Known coexpressed genes in various species include NTPX2, GAL, PDYN, ENTPD3 (extonucleoside triphosphate diphosphohydrolase 3) and CART. These transcripts were not identified in our human array analysis as they either were expressed in other areas of the brain, leading to a low SAM ranking (NPTX2, GAL, CART) or because the expression was classified as absent in most samples (PDYN, ENTPD3), although the QRT-PCR analysis indicated moderately decreased expression of these genes in narcolepsy (see results).