Exploring the Molecular Landscape of Learning and Memory
The nuanced dynamics of local synaptic biology shape the formation, stability, and adaptability of neuronal networks. Leveraging cutting-edge technologies, our endeavor is to unravel the complex molecular pathways dictating synaptic neurotransmission with spatial and temporal resolution. Our overarching objective is to illuminate the intricate dance that underlies learning and memory, two fundamental pillars of human cognition.
How do neurons regulate their mitochondria at synapses to meet synaptic demands?
In addition to fueling cellular energy with ATP, mitochondria, often referred to as the “powerhouses of cells,” hold vital significance for neurons due to their capacity for calcium buffering. For instance, synaptic activity triggers an increase in mitochondrial presence at synapses, while dysfunction in these organelles can lead to diminished neurotransmitter release, impaired synaptic plasticity, oxidative damage, and apoptosis. Despite the critical role of mitochondrial health in neuronal function, the precise molecular mechanisms governing this importance remain elusive. We tackle these fundamental questions in mitochondrial biology by implementing proximity labeling, imaging, and metabolomics approaches in resting and activated neurons. We combine proximity labeling with RNA-sequencing, ribosome profiling, and mass spectrometry to study the activity-dependent regulation of mitochondria-related RNAs at the synapse, with an emphasis on their upstream open reading frames (uORFs).
How does synaptic diversity mediate responses to activity in vitro and in vivo?
The extensive array and diversity of RNAs and proteins identified within synapses underscore the remarkable molecular complexity of the mammalian brain. This complexity is further accentuated by the differential expression of multiple isoforms of a single protein across various cell types and brain regions. Such protein combinations contribute significantly to the diverse nature of synapses and their dynamic capabilities, allowing them to temporally discern and interpret patterns of activity, thereby shaping physiological outcomes.
Consequently, conventional population-based measurements often fail to unveil the intricate molecular mechanisms underlying synaptic function. Understanding these unique activity-dependent molecular dynamics at different synapses is paramount to unraveling the distinctive features of synaptic transmission and plasticity, as well as their varying susceptibilities to neurological diseases.
To delve deeper into this diversity and its regulatory principles, we leverage our TurboID platform to analyze primary neurons and the mouse brain. This endeavor promises to shed further light on the underlying mechanisms governing synaptic function and their implications for neurological health.
What are the species-specific synaptic regulatory mechanisms and how do they go awry in autism?
The dramatic increase in neuron numbers, expanding a thousandfold from mice to humans, has led to a proliferation of synaptic connections capable of expressing a greater diversity of protein combinations. This surge in molecular complexity has not only facilitated the emergence of intricate behavioral patterns but has also heightened susceptibility to deleterious mutations, resulting in brain disorders like autism. While animal models remain invaluable for studying certain behavioral and neurological aspects associated with autism, they fall short of fully capturing the complexity of the human condition, particularly its intricate cognitive and social dimensions. Consequently, there is a need to explore synaptic molecular dynamics across species to gain insights into the evolutionary pressures shaping brain function and behavior. Such comparative analyses promise to elucidate the molecular underpinnings of species-specific cognitive traits and adaptive behaviors. To study human synapses, we implement our synaptic TurboID in human induced pluripotent stem cell (hiPSC)-derived neurons.
Activity-dependent alterations in synaptic strength form the cornerstone of the most widely accepted model for learning and memory. Consequently, genetic variations impacting synaptic plasticity often lead to intellectual disability. Intriguingly, many of these mutations occur in genes involved in RNA localization and translation. Autism spectrum disorder (ASD) presents a complex neurodevelopmental challenge arising from a diverse array of mutations, each with variable penetrance and resulting in a broad spectrum of symptoms. Among the frequently mutated genes in ASD are those implicated in synaptic communication, with key roles in RNA binding, RNA localization, and synthesis of synaptic proteins. Despite this knowledge, our understanding of how these mutations translate into the varied autism phenotypes remains incomplete. Thus, there is an imperative to explore how synapses undergo remodeling in response to neuronal activity and how dysregulation of synaptic RNA contributes to ASD pathology. We study the molecular consequences of autism mutations on synaptic plasticity by combining CRISPR-Cas9 with TurboID in hiPSC-derived neurons.