A serotonergic axon-cilium synapse drives nuclear signaling to alter chromatin accessibility

Shu-Hsien Sheu (1, 2, 3) , Srigokul Upadhyayula (4, 5) , Vincent Dupuy (6) , Song Pang (1) , Fei Deng (7) , Jinxia Wan (7) , Deepika Walpita (1) , H. Amalia Pasolli (1) , Justin Houser (3) , Silvia Sanchez-Martinez (1) , Sebastian Brauchi (1, 8) , Sambashiva Banala (1) , Melanie Freeman (1) , C. Shan Xu (1) , Tom Kirchhausen (9, 2) , Harald Hess (1) , Luke Lavis (1) , Yulong Li (7) , Séverine Chaumont-Dubel (6) , David Clapham (2, 3)

1 HHMI Janelia - Janelia Research Campus [Ashburn]
2 HMS - Harvard Medical School [Boston]
3 Boston Children's Hospital
4 UC Berkeley - University of California [Berkeley]
5 Chan Zuckerberg BioHub [San Francisco, CA]
6 IGF - Institut de Génomique Fonctionnelle
7 Peking University [Beijing]
8 Universidad Austral de Chile
9 Boston Children's Hospital

Chemical synapses between axons and dendrites mediate neuronal intercellular communication. Here, we describe a synapse between axons and primary cilia: the axo-ciliary synapse. Using enhanced focused ion beam-scanning electron microscopy on samples with optimally preserved ultrastructure, we discovered synapses between brainstem serotonergic axons and the primary cilia of hippocampal CA1 pyramidal neurons. Functionally, these cilia are enriched in a ciliary-restricted serotonin receptor, the 5-hydroxytryptamine receptor 6 (5-HTR6). Using a cilia-targeted serotonin sensor, we show that opto- and chemogenetic stimulation of serotonergic axons releases serotonin onto cilia. Ciliary 5-HTR6 stimulation activates a non-canonical Gαq/11-RhoA pathway, which modulates nuclear actin and increases histone acetylation and chromatin accessibility. Ablation of this pathway reduces chromatin accessibility in CA1 pyramidal neurons. As a signaling apparatus with proximity to the nucleus, axo-ciliary synapses short circuit neurotransmission to alter the postsynaptic neuron's epigenetic state.

Mots clés: FIB-SEM; GPCR signaling; chromatin accessibility; fluorescence lifetime imaging; histone modification; nuclear actin; primary cilia; pyramidal neurons; serotonin

Domaines: Neurobiologie

Shu-Hsien Sheu, Srigokul Upadhyayula, Vincent Dupuy, Song Pang, Fei Deng, et al.. A serotonergic axon-cilium synapse drives nuclear signaling to alter chromatin accessibility. Cell, 2022, 185 (18), pp.3390-3407. ⟨10.1016/j.cell.2022.07.026⟩. ⟨hal-03796396⟩