Here’s a few posters that caught my eye at SfN. Click the meeting planner for the full abstract
Optimizing two-photon activation of channelrhodopsin-2 for stimulation at cellular resolution
J. P. RICKGAUER1,2, D. W. TANK1,2;
Spiral pattern of 2-photon excitation can drive neurons to spike. A low NA objective helps. Need to do piezo-based Z-scanning if you use high NA, don’t with low NA.
*T. H. CHIA, M. J. LEVENE;
A cute method to image 1mm into cortex with 2-photon imaging. They used 2-6 month old mice. The just took a triangular prism whose hypotenuse was silvered and stuck it in the cortex. Then they internally reflected the beam off the prism and fired it sideways into cortex. Got good SNR to 300um lateral distance. Some clippling of beam at edges of the prism gave somewhat inconsistent spatial resolution.
Self-complementary adeno-associated viral vectors for fast, efficient labeling of neurons and astrocytes in visual cortex in vivo
R. L. LOWERY1, Y. ZHANG2, C. LAMANTIA1, B. K. HARVEY3, A. K. MAJEWSKA1;
AAV is the way to go for expression of GECIs and ChR2 in vivo, but it takes a long time to express at high levels (2 weeks). They show that using a double stranded DNA version of AAV rather than single stranded gets protein expression up high much faster. Very high expression after one week. This is because the virus doesn’t need to take the time to make the second strand before expressing the protein. See Xiao, X J. Virol 1998
Detection of single action potentials in vitro and in vivo with genetically-encoded Ca2+ sensors
S. MEYER ZUM ALTEN BORGLOH1, D. J. WALLACE2, S. ASTORI3, Y. YANG3, M. BAUSEN3, S. KUGLER4, M. MANK5, O. GRIESBECK5, J. NAKAI6, A. MIYAWAKI6, A. E. PALMER7, R. Y. TSIEN7, R. SPRENGEL3, J. N. D. KERR2, W. DENK3, M. T. HASAN3;
Everything in the poster was in the Nature Methods paper. Conversation reveled that YC3.60 works as well or better than D3cpv. Only have done up to whisker evoked stimulation, no imaging of spontaneous YC3.60 signals yet.
Characterization of improved probes for the hybrid voltage sensor method of voltage imaging
D. WANG1, Z. ZHANG2, B. CHANDA1, M. B. JACKSON1;
A nice little sensor optimization poster. They took the hVOS hybrid voltage sensor of dipicrylamine with membrane tethered GFP and improved it by changing the chromophore to Cerulean, and by using the “membrane-staple” strategy. Having membrane anchors on both the N and C-termini gave better quenching. Fast response, ~0.5ms, and 20% dF/F.
Crystal structure of the genetically encoded calcium indicator gcamp2
*J. AKERBOOM1, L. TIAN1, S. VISWANATHAN1, S. A. HIRES1, J. S. MARVIN1, E. R. SCHREITER2, L. L. LOOGER1;
Jasper made crystal structures of G-CaMP2 in the apo and bound states. Bound states crystalized as a heterodimer, but he was able to also crystalize the monomer. The structures show a pore to the chromophore in the apo state that is plugged in the Ca-bound state. Thus, the quenched apo state is due to solvent access to the chromophore. This structural data should help rational design of better G-CaMP sensors.