Defining the Circuit, Synaptic, and Molecular Mechanisms Linking Intracellular Ca2+ Release to Learning Using Subcellularly-Targeted Manipulations and Imaging Techniques in Dendrites in Vivo

Project Summary/Abstract Candidate Goals and Mission Relevance: The applicant’s broad, long-term objective is to investigate how high- (circuit/behavioral) and low- (subcellular/molecular) level organizational principles of the brain cooperate to drive learning. The proposed research activities will build a foundation for this long-term goal and, in so doing, will

promote BRAIN 2025 Report goals by integrating new technological and conceptual approaches to causally link intracellular Ca2+ release (ICR) from endoplasmic reticulum (ER) to neural activity dynamics and behavior. Project description: Dendritic Ca2+ is central to neural plasticity mechanisms allowing animals to adapt to the

environment. ICR has long been thought to shape these mechanisms. The applicant recently carried out the first investigation of ICR in mammalian neurons in vivo to uncover how this subcellular phenomenon shapes experience-dependent feature selectivity across the dendritic arbor of pyramidal neurons (PNs) in mouse

hippocampal area CA1. This work raises important questions regarding when, where, and how ICR is engaged to support learning. The applicant will address these questions in the following Aims: Aim 1. Characterize plasticity-associated ER Ca2+ dynamics in dendrites in vivo (K99): To achieve this Aim, the applicant will perform simultaneous dual-color, dual-plane in vivo 2-photon imaging of cytosolic and ER-

resident Ca2+ in dendrites of single CA1 PNs during head-fixed spatial navigation of novel virtual environments. Aim 2. Define the synaptic logic tying intracellular Ca2+ release to in vivo synaptic plasticity (K99/R00): The applicant will first create a novel molecular tool to optogenetically induce ICR (Aim 2.1; K99). The applicant

will then combine this precise interventional tool with single-cell imaging, inducible blockade of presynaptic release, and optogenetic dampening of ICR to dissect the synaptic logic by which ICR participates in plasticity induction in behaving mice. (Aim 2.2; R00). Aim 3. Dissect excitatory circuit-molecular mechanisms driving intracellular Ca2+ release in vivo (R00):

The candidate will optogenetically activate specific excitatory projections onto distinct dendritic compartments of single CA1PNs while monitoring ER Ca2+ dynamics in behaving mice. Local pharmacological manipulations will dissect contributions of the two canonical pathways that convert presynaptic excitatory input to postsynaptic ICR.

Career development plan: The applicant will extend a highly complementary Co-Mentorship arrangement between Drs. Franck Polleux and Attila Losonczy who possess deep expertise in cellular/molecular/genetic and in vivo/behavioral approaches, respectively. The applicant will receive robust consultative support from Dr.

Stefano Fusi of Columbia’s Center for Theoretical Neuroscience and Dr. Darcy Peterka, Director of Cellular Imaging at Columbia’s Zuckerman Institute. The applicant’s research and transition to independence will benefit from this strong mentorship team, state-of-the-art facilities, all necessary equipment, and numerous Professional

Development resources offered through the Columbia Office of Postdoctoral Affairs, the Zuckerman Institute, and the BRAIN Initiative.