Biophysical Society Thematic Meeting - June 28-July 1, 2015

New Biological Frontiers Illuminated by Molecular Sensors and Actuators

Monday Speaker Abstracts

Ratiometric in vivo Imaging with “Twitch” Calcium Sensors Oliver Griesbeck . Max-Planck-Institute of Neurobiology, Martinsried, Germany.

I will describe a collection of FRET-based calcium biosensors with a minimized calcium binding domain and thus a reduced number of calcium binding sites per sensor. They are based on the C- terminal lobe of Troponin C and were characterized by NMR and SAXS. Their FRET responses were optimized by a large scale functional screen in bacterial colonies, refined by a secondary screen in hippocampal neurons. Further improvements in brightness lead to sensors with excellent properties in vivo. When imaging neuronal activity in mouse cortex and olfactory bulb the performance of the most sensitive variants matched that of synthetic calcium dyes. Moreover, improved Twitch sensors allowed for high resolution imaging of calcium fluctuations during tissue migration and activation of T-lymphocytes upon encountering their antigen. The sensitivity, brightness, biocompatibility and linear response properties should make them widely useful for cellular imaging applications.

Mapping Memory Circuits in the Drosophila Brain Ann-Shyn Chiang . National Tsing Hua University, Hsinchu, Taiwan.

Long-term memory (LTM) involves gene activation and new protein synthesis that alters synaptic connections between neurons. Knowing where these genes and proteins interact is critical for understanding LTM formation. Recently, we showed that new proteins in the mushroom body (MB) efferent MB-V3 and afferent DAL neurons are necessary for LTM formation in Drosophila. Here, using a temperature-sensitive ribosomal-cleavage toxin to block protein synthesis, we report an ensemble of neurons where new proteins induced after learning are necessary for LTM formation. Monitoring gene activities with a photoconvertible fluorescent protein KAEDE, we showed that different memory neurons use different gene products at different times during memory formation. Our findings begin to reveal a spatiotemporal neural ensemble storing protein-synthesis-dependent LTM in the Drosophila brain.

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