Pharmacological Validation of Candidate Causal Sleep Genes Identified in an N2 Cross

Abstract

Abstract: Despite the substantial impact of sleep disturbances on human health and the many years of study dedicated to understanding sleep pathologies, the underlying genetic mechanisms that govern sleep and wake largely remain unknown. Recently, the authors completed large-scale genetic and gene expression analyses in a segregating inbred mouse cross and identified candidate causal genes that regulate the mammalian sleep-wake cycle, across multiple traits including total sleep time, amounts of rapid eye movement (REM), non-REM, sleep bout duration, and sleep fragmentation. Here the authors describe a novel approach toward validating candidate causal genes, while also identifying potential targets for sleep-related indications. Select small-molecule antagonists and agonists were used to interrogate candidate causal gene function in rodent sleep polysomnography assays to determine impact on overall sleep architecture and to evaluate alignment with associated sleep-wake traits. Significant effects on sleep architecture were observed in validation studies using compounds targeting the muscarinic acetylcholine receptor M3 subunit (Chrm3) (wake promotion), nicotinic acetylcholine receptor alpha4 subunit (Chrna4) (wake promotion), dopamine receptor D5 subunit (Drd5) (sleep induction), serotonin 1D receptor (Htr1d) (altered REM fragmentation), glucagon-like peptide-1 receptor (Glp1r) (light sleep promotion and reduction of deep sleep), and calcium channel, voltage-dependent, T type, alpha 1I subunit (Cacna1i) (increased bout duration of slow wave sleep). Taken together, these results show the complexity of genetic components that regulate sleep-wake traits and highlight the importance of evaluating this complex behavior at a systems level. Pharmacological validation of genetically identified putative targets provides a rapid alternative to generating knock out or transgenic animal models, and may ultimately lead towards new therapeutic opportunities.

Keywords::

• genetics
• pharmacology
• rodent
• sleep
• translation

ACKNOWLEDGMENTS

Assistance from Merck's Laboratory Animal Resources Staff (Central Pharmacology, Merck Research Laboratories) for expert animal handling and treatments are much appreciated. We would also like to acknowledge Eric Schadt for his encouragement to pursue the integrative genomics research approach and for many useful discussions. This work was supported by a research grant from Merck and Co. (F.W.T.) and by the Army Research Office (A.R.O.), award number DAAD19-02-1-0038 from the Defense Advance Research Projects Agency. Investigators from the sponsoring institution (Merck/Rosetta) were involved in data analysis (genotyping, QTL identification, Baeysian network construction and statistics) and interpretation of the results.

Declaration of interest: J.I.B, A.L.G., A.L.W, J.M., S.G., J.B., S.M.D, S.V.F., A.K., J.J.R., and C.J.W. are or have been employed by Merck & Co., Inc. (USA) and potentially own stock and/or stock options in the company. The authors report no other conflicts of interest. The authors alone are responsible for the content and writing of the paper.