Calcium Signals in Neurons During Early Development: Experiments and Theory

• Applicants: Privatdozent Dr. Friedrich Johenning; Professor Dr. Igor M. Sokolov, since 11/2019
• Subject Area: Developmental Neurobiology ; Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 327008147

• Final Report Year: 2021

Final Report Abstract

Sensory cortices are composed of ascending sensory circuits that relay sensory information from the periphery and recurrent intracortical circuits. Dendritic trees of neurons are shaped during development and determine which circuits contribute to the neuronal input space. To date, circuit-specific aspects of dendritic development and the underlying mechanisms are poorly understood. This project investigated dendritic development in layer 2 of the piriform cortex, a threelayered palaeocortex that displays clear vertical segregation of sensory and recurrent circuits. Our results suggest that dendritic development occurs in distinct developmental phases with different circuit-specific properties. The critical question was how neuronal Ca2+ signals, the interface between electrical neuronal activity and biochemical and strucural changes, would relate to the different growth patterns. In general, we found evidence for the concept of dendritotrophy by neuronal Ca2+ signaling, more robust activity-related Ca2+ signaling correlated with more elaborate dendritic structures. Our key finding in this respect was the circuit and cell-type specific pruning of distal dendritic branches in the piriform cortex. We only observed pruning of distal apical dendrites receiving layer 1a sensory in- puts in layer 2b neurons, but not in layer 2a neurons. Pruning was biased toward shorter dendritic branches. Using electrophysiology, Ca2+ imaging and modeling, we demonstrated how NMDAR-dependent supralinear stimulus-response behavior could support the survival and growth of long dendritic branches. Nonlinear dendritic properties could therefore be involved in dendritic development.

Publications

• (2017) SamuROI, a Python-Based Software Tool for Visualization and Analysis of Dynamic Time Series Imaging at Multiple Spatial Scales. Frontiers in Neuroinformatics 11:1014–1059
  Rueckl M, Lenzi SC, Moreno-Velasquez L, Parthier D, Schmitz D, Ruediger S, Johenning FW
  
• (2018) Voltage gated calcium channel activation by backpropagating action potentials downregulates NMDAR function. Frontiers in Cellullar Neuroscience
  Theis AK, Rózsa B, Katona G, Schmitz D, Johenning FW
  
• (2020) Circuit-specific dendritic development in the piriform cortex. Eneuro 7:ENEURO.0083-20.2020
  Moreno-Velasquez L, Lo H, Lenzi S, Kaehne M, Breustedt J, Schmitz D, Rüdiger S, Johenning FW