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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.