Title: Cellular and neural circuit mechanisms of developmental synapse pruning in the cerebellum

Speaker: Masanobu Kano ^1,2

1. Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan

2. International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo Institutes for Advanced study (UTIAS), The University of Tokyo, Tokyo 113-0033, Japan

Time: 13:00-15:00, December 3, 2019

Location: B101, Lui Che Woo Building

Abstract:

In the neonatal rodent cerebellum, Purkinje cells (PCs) receive excitatory synaptic inputs from multiple climbing fibers (CFs). PCs are initially innervated by more than five CFs with similar synaptic strengths. During the first three postnatal weeks, redundant CFs are eliminated and most PCs become innervated by single CFs. This developmental process, termed CF synapse elimination, consists of at least four distinct phases: (1) selective strengthening of a single CF out of multiple CFs innervating each PC from postnatal day 3 (P3) to around P7 (functional differentiation), (2) translocation and expansion of innervation territory of the strongest CF (‘winner’ CF) to PC dendrites from P9 (dendritic translocation), (3) elimination of somatic synapses of the ‘winner’ CF and those of weaker CFs (‘loser’ CFs) from P7 to around P11 (early phase of CF elimination), (4) elimination of remaining somatic CF synapses from around P12 to P17 in a manner dependent on excitatory synapse formation from parallel fibers (PFs) onto PC dendrites (late phase of CF elimination). Besides CF synapse elimination, pruning of redundant PF synapses from the proximal portion of PC dendrite occurs from ^~P15 to ^~P30, which established the mature pattern of segregated CF and PF innervation of PC dendrites. In this talk, I will make an overview about cellular/molecular mechanisms of CF synapse elimination, and present our unpublished data to discuss how neural activity regulates the distinct phases of CF synapse elimination.

Host: Dr. Yulong Li