Internal Seminar: Skoglund Unit and De Schutter Unit

Join us for September's first Internal Seminar Series on September 18, from 17:00 to 18:00 in C700 (Lab3). This month's second seminar features the Structural Cellular Biology Unit (Ulf Skoglund) and the Computational Neuroscience Unit (Erik De Schutter).

Structural Cellular Biology Unit (Ulf Skoglund)

Speaker : Setsuko Nakanishi

Title : High-resolution FIB-SEM reveals plasma membrane dynamics at the neuronal-glial synaptic interface

Abstract : Electron microscopic studies have revealed various features of synapses, contributing much to the understanding of synaptic function.  After exocytosis of neurotransmitters, synaptic vesicles (SV) are thought to be recovered predominantly by endocytosis.  SV recycling is one of the best-studied cellular events, however, most aspects of SV recycling have been studied at active zones and it is still difficult to understand SV recycling as a whole. The aim of this study is to find structures related to SV endocytosis and recycling in a whole synapse including synapse-surrounding glial processes.  Focused ion beam milling and scanning electron microscopy (FIB-SEM) was chosen for the present study, because it is suitable for mesoscale imaging without making sections. 10 nm consecutive slice images revealed endocytic structures and plasma membrane folds in both presynaptic plasma membrane and synaptic plasma membrane facing glial processes.  Also observed were tubulo-vesicular structures close proximity to synaptic mitochondria and large endosomes, chains of synaptic vesicles, sporadic, thick extracellular matrix, and regional differences in electron density in the plasma membrane at neuronal-glial interface.  These characteristic features observed in this study may provide the structural cues to study neuronal-glial interface dynamics, especially glutamate-glutamine cycle.

Computational Neuroscience Unit (Erik De Schutter)

Speaker : Sungho Hong

Title : How does the brain know summer is gone?

Abstract : The fundamental processes underlying the function and behavior of most life forms on Earth, such as plants and animals, are locked in a circadian rhythm that is synchronized with the 24-hour cycle of light and darkness. Furthermore, organisms can adapt the rhythm to changes in this cycle, such as seasonal variation in day length, which is crucial for survival. In this talk, I will explain how the suprachiasmatic nucleus (SCN), a master clock for the circadian rhythm in the brain, can memorize and encode information about day length. I will present our recent findings that explain how signaling in the SCN neural circuit organizes 24-hour rhythmic activity of gene expression networks within individual neurons into an oscillator network. Crucially, the network structure is asymmetric, and I will explain how this leads to a unique computational property that can explain various features of the SCN dynamics and circadian behavior. If time permits, I will briefly explain about our hypothesis for the underlying physiological mechanism - the tunable balance between excitation and inhibition in the SCN neural circuit.