Immortal orexin cell transplants restore motor-arousal synchrony during cataplexy

• Published in: Current biology 2023-04, Vol.33 (8), p.1550-1564.e5
• Main Authors: Pintwala, Sara K., Fraigne, Jimmy J., Belsham, Denise D., Peever, John H.
• Format: Article
• Language: English
• Subjects: Animals; arousal; Arousal - physiology; cataplexy; Cataplexy - therapy; Cell Transplantation; cell transplantation therapy; dorsal raphe; Dorsal Raphe Nucleus; hypocretin; Mice; narcolepsy; orexin; Orexins - genetics; Orexins - metabolism; Proteomics; sleep; wakefulness; Wakefulness - physiology
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2023.03.077

Waking behaviors such as sitting or standing require suitable levels of muscle tone. But it is unclear how arousal and motor circuits communicate with one another so that appropriate motor tone occurs during wakefulness. Cataplexy is a peculiar condition in which muscle tone is involuntarily lost during normal periods of wakefulness. Cataplexy therefore provides a unique opportunity for identifying the signaling mechanisms that synchronize motor and arousal behaviors. Cataplexy occurs when hypothalamic orexin neurons are lost in narcolepsy; however, it is unclear if motor-arousal decoupling in cataplexy is directly or indirectly caused by orexin cell loss. Here, we used genomic, proteomic, chemogenetic, electrophysiological, and behavioral assays to determine if grafting orexin cells into the brain of cataplectic (i.e., orexin−/−) mice restores normal motor-arousal behaviors by preventing cataplexy. First, we engineered immortalized orexin cells and found that they not only produce and release orexin but also exhibit a gene profile that mimics native orexin neurons. Second, we show that engineered orexin cells thrive and integrate into host tissue when transplanted into the brain of mice. Next, we found that grafting only 200–300 orexin cells into the dorsal raphe nucleus—a region densely innervated by native orexin neurons—reduces cataplexy. Last, we show that real-time chemogenetic activation of orexin cells restores motor-arousal synchrony by preventing cataplexy. We suggest that orexin signaling is critical for arousal-motor synchrony during wakefulness and that the dorsal raphe plays a pivotal role in coupling arousal and motor behaviors. [Display omitted] •Immortalized hypothalamic orexin cells express and release orexin•Transplanting orexin cells to the dorsal raphe reduces cataplexy in narcoleptic mice•Chemogenetic strategies can be used to enhance orexin release in transplanted cells•Chemogenetic activation of immortalized orexin cells prevents cataplexy Narcolepsy is a sleep disorder caused by loss of hypothalamic orexin neurons. An important feature of narcolepsy is episodes of muscle atonia during wakefulness, called cataplexy. Pintwala et al. show that transplantation of immortalized hypothalamic orexin neurons to the dorsal raphe of orexin-deficient mice reduces the incidence of cataplexy.