Synaptic protein translation as an interface between circadian rhythms and the need for sleep

About This Grant

PROJECT SUMMARY: This R21 proposal seeks to uncover how sleep and circadian rhythms (CR) regulate protein synthesis at neuronal synapses, key cellular sites for learning and memory, by defining the “synaptic translatome”: newly synthesized proteins localized at synapses. Sleep is essential for brain health and survival. Sleep need accumulates during wake and is resolved only by sleep. Although sleep behavior is governed by specific brain circuits, sleep need is distributed throughout the nervous system. Synapses are central to this distributed sleep need, as they undergo plastic changes during wake and are subsequently remodeled during sleep to support synaptic homeostasis, memory consolidation, and brain development. Synapses have thus emerged as a conserved and distributed 1. locus of sleep need, 2. target of restorative sleep function, and 3. site of dysfunction with sleep loss. Neurons rely on localized protein translation at synapses, far from the cell body, to support these plastic changes. The timing of this process is influenced by the circadian clock, a cellular mechanism involving “clock genes” that operate in nearly all cells. Previous multi-omic studies of purified forebrain synapses revealed that both CR and sleep need regulate the trafficking of mRNAs to synapses and the timing of their translation. Defining the synaptic translatome in response to wake/sleep states and circadian time is essential to revealing the biochemical basis of sleep’s restorative functions and its interactions with the CR. This research also addresses the intersection between sleep, synaptic development, and neurodevelopmental disorders (NDDs) such as Autism Spectrum Disorder (ASD) and Schizophrenia (SCZ). Disruption of sleep and circadian rhythms is a common feature in NDDs, and many NDD-associated genes encode synaptic proteins, such as SHANK3. Prior work using SHANK3+/- mice, a model for genetic vulnerbaility for ASD and SCZ, demonstrated that early life sleep disruption (ELSD, postnatal days 14–21) leads to persistent, sex-specific behavioral changes, highlighting an interaction between sleep, genetic vulnerability, and sex. Synapse-specific proteomic analysis in these mice showed that ELSD disrupts synapse maturation, particularly affecting protein synthesis and mRNA biology. To build on these findings, the proposal uses biorthogonal non- canonical amino acid tagging (BONCAT) to label newly synthesized proteins, combined our established synapse fractionation and quantitative proteomics to define the synaptic translatome. Aim 1 will characterize how the synaptic translatome is shaped by CR and sleep deprivation across development in juvenile, adolescent, and adult mice, across brain regions including cortex, hippocampus, and striatum. Aim 2 will determine how ELSD alters the synaptic translatome in wild-type and SHANK3+/- mice, to better understand how sleep disruption impacts synapse maturation in genetically vulnerable brains. This R21 will establish BONCAT as a powerful discovery platform to study synaptic protein synthesis in vivo, enabling novel insights into the mechanisms of sleep function, and how its disruption contributes to the etiology of neurodevelopmental disorders.