SNSS

Newborn neurons in the developing brain migrate from the site of birth to their destination for integration into specific neural circuits.  Neuronal migration is highly directional movement along either radial or tangential dimension of the cylindrical neural tube.  Migrating neurons polarize to extend the leading process in the direction of the travel, and then translocate the cell body containing the nucleus into the leading process.  In this lecture, we will discuss the molecular and cellular dynamics of neuronal migration in comparison with other cell types. 

Ayala R, Shu T, Tsai LH (2007) Trekking across the Brain: The Journey of Neuronal Migration. Cell 128: 29-43.

Ridley AJ, Schwartz MA, Burridge K, Firtel RA, Ginsberg MH, Borisy G, Parsons JT, Horwitz AR (2003) Cell migration: integrating signals from front to back. Science 302:1704-1709.

Tsai LH, Gleeson JG (2005) Nucleokinesis in neuronal migration. Neuron 46:383-388.

The behavioral response of C. elegans to temperature called thermtaxis is an ideal system for elucidation of the mechanism by which animals sense temperature and memorize temperature. The neural circuit essential for this thermotaxis behavior was identified and several genes required for thermotaxis were isolated. Thermotaxis was further shown to be the behavioral outcome of associative learning between temperature and feeding state. To address how genes acting in the neural circuitry generate behavior, the activities of the component neurons in the thermotaxis neural circuit in live animals were monitored using a genetically encodable calcium sensor. Systematic optical imaging of neurons in the thermotaxis circuit combined with application of computational biology may ultimately propose a new concept for dynamics of neural circuit controlling behavior.

Mori, I., Sasakura, H. and Kuhara, A. (2008) Worm thermotaxis: a model system for analyzing thermosensation and neural plasticity, Curr Opin Neurobiol, doi:10.1016/j.conb.2007.11.010

Kodama, E., Kuhara, A., Mohri-Shiomi, A., Kimura, K. D., Okumura, M., Tomioka, M., Iino, Y. and Mori, I.
(2006) Insulin-like signaling and the neural circuit for integrative behavior in C. elegans.
Genes Dev. 20: 2955-2960.

Mori, I. and Ohshima,Y.
(1995) Neural regulation of thermotaxis in Caenorhabditis elegans.
Nature 376: 344-348.

The proper functioning of the nervous system depends on precise interconnections of distinct types of neurons.  Therefore, understanding the molecular mechanisms of synaptic specificity ― the specificity with which connections form between neurons ― is a central issue in modern neuroscience.  We have used the Drosophila neuromuscular system to study this problem.  In this lecture, I will talk about the following two new developments.  (1) Using microarray, we identified Wnt4 as a repulsive target cue.  Our results showed that target specificity is determined not only by an attractive signal from the target cell but also by a negative signal from neighboring non-target cells (ref.2), (2) live-imaging analysis of the process of synapse formation revealed in vivo role of a cell adhesion molecule in synaptic induction (ref.3).

1. Benson, D.L., Colman, D.R., & Huntley, G.W.. Molecules, maps and synapse specificity. Nat. Rev. Neurosci. 2, 899-909 (2001).

2. Inaki, M., Yoshikawa, S., Thomas, J.B., Aburatani, H. & Nose, A. Wnt4 is a local repulsive cue that determines synaptic target specificity. Curr. Biol. 17, 1574-1579 (2007).

3.Kohsaka, H., Takasu, E. & Nose, A.  In vivo induction of postsynaptic molecular assembly by the cell adhesion molecule Fasciclin2. J. Cell Biol. 179 1289-1300 (2007).

The responses of cortical neurons in response to sensory stimulation are diverse. The goal of this study is to elucidate the cellular properties and network architecture that underlie the firing behaviors of cortical neurons.  We first perform multiple whole-cell recordings in a slice preparation to characterize the synaptic and intrinsic
membrane properties of pyramidal cells and interneurons as well as their patterns of connections.  We then use the measured parameters to perform simulations both in vitro and with a computer to determine salient firing behaviors that arise from the network. Surprisingly, we were able to account for many of the firing behaviors and receptive field properties of cortical neurons with a simple network of pyramidal and inhibitory neurons. Finally,  we use mean field theoretical techniques borrowed from Physics to elucidate general principles that are applicable to the nervous system as a whole.

Reyes AD (2003) Synchrony-dependent propagation of firing rate in iteratively constructed networks in vitro. Nature Neuroscience 6:593-599 (see also Segev, Nature Neuroscience 6:543-544; News & Views).

Cateau H & Reyes AD (2006) Relation between single neuron and population spiking statistics and effects on network activity. Phys. Rev. Letters 96.

A.M. Oswald, M.L. Schiff, A.D. Reyes (2006) Synaptic Mechanisms Underlying Auditory Processing.  Current Opinion in Neurobiology 16(4): 371-376