Translational profiling of hypocretin neurons identifies Lhx9 as necessary for normal development of the hypocretinergic system.

The immense molecular diversity of neurons challenges our ability to deconvolve the relationship between the genetic and the cellular underpinnings of neuropsychiatric disorders. Hypocretin (orexin) containing neurons of the lateral hypothalamus are clearly essential for the normal regulation of sleep and wake behaviors, and have been implicated in feeding, anxiety, depression and reward. However, little is known about the molecular phenotypes of these cells, or the mechanism of their specification. We have generated a Hcrt bacTRAP line for comprehensive translational profiling of these neuronsin vivo. From this profile, we have identified 188 transcripts, as enriched in these neurons, in additions to thousands more moderately enriched or nominally expressed. We validated many of these at the RNA and protein level, including the transcription factor Lhx9. Lhx9 protein is found in a subset of these neurons, and ablation of these gene results in a 30% loss of Hcrt neuron number, and a profound hypersomnolence in mice.This data suggests that Lhx9 may be important for specification of some Hcrt neurons, and the subsets of these neurons may contribute to discrete sleep phenotypes.

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Dalal J, Roh JH, Maloney SE, Akuffo A, Shah S, Yuan H, Wamsley B, Jones WB, de Guzman Strong C, Gray PA, Holtzman DM, Heintz N, Dougherty JD