Polleux Lab
Circuit development, evolution and maintenance
A Sneak Peak At Some of Our Tools
In Utero Electroporation and Neuron Reconstruction
We developed a new, open-source, reconstruction platform for mapping the size and spatial distribution of E and I synapses received by individual, genetically-labeled, layer 2/3 cortical pyramidal neurons (PNs) in vivo. We mapped over 90,000 E and I synapses across twelve L2/3 PNs and uncovered structured organization of E and I synapses across dendritic domains as well as within individual dendritic segments in these cells.
The image describes the workflow for excitatory and inhibitory synaptic reconstruction across whole neurons with Vaa3D Synapse Detector program developed in collaboration with the Allen Institute for Brain Science.
This work is featured in this paper by Daniel Iascone
Rabies Tracing and Neural Connectivity Reconstruction
We have adapted monosynaptic pseudo-rabies tracing to quantitatively map the inputs received by specific pyramidal neurons in the mouse cortex using combination of sparse in utero cortical electroporation (IUCE) using a Cre- dependent expression FLEX-plasmid expressing TVA receptor, N2c Glycoprotein, and histone- tagged-GFP (hGFP). TVA expression enables infection by EnvA pseudotyped G-deleted N2c rabies virus (Rabv), while the N2c glycoprotein is required for trans- synaptic and retrograde spread of the virus. Hence, sparse Cre-induced expression of hGFP, TVA and N2c in a sparse population of layer 2/3 pyramidal neurons primes these ‘starter’ neurons for infection and trans- synaptic labeling by the pseudotype. Ewoud Schmidt in our lab also developed a computational pipeline to map the 3D position of all traced neurons from multiple mouse brains in a common reference Atlas (Allen Brain Atlas).
This work is featured in this paper by Ewoud Schmidt.
2-Photon Calcium Imaging in awake behaving mice
We implemented in vivo 2-photon (2P) Ca2+ imaging in awake behaving mice to probe either in cortical or hippocampal circuit function. For example, in close collaboration with our colleague in Attila Losonczy's lab , Heike Blockus has used this approach to probe changes in the response properties of control or Robo2-deficient in hippocampal CA1 pyramidal neurons in the same mice. She found that reduction by 40% of inputs from CA3 in Robo2-deficient CA1 PNs significantly alters the fraction of spatially tuned CA1 PNs and alters spatial coding. Ewoud Schmidt in our lab also used in vivo 2-photon Ca2+ imaging to demonstrate that humanization of SRGAP2C expression in layer 2/3 of the barrel cortex increases the reliability and selectivity of sensory evoked responses.
This work is featured in the latest papers of Ewoud Schmidt and Heike Blockus.
