Graduate School of Frontier Biosciences, Osaka University

Japanese

"Genetic dissection of cortical interneuron subtypes: From cell type specification to circuit formation and function" Dr. Hiroki Taniguchi (Development and Function of Inhibitory Neural Circuits, Max Planck Florida Institute for Neuroscience)

Date/Time

December 8, 13:00-14:30


Place

Seminar Room (3F), Nanobiology building


Speaker

Hiroki Taniguchi
Research Group Leader, Development and Function of Inhibitory Neural Circuits, Max Planck Florida Institute for Neuroscience

Title

Genetic dissection of cortical interneuron subtypes: From cell type specification to circuit formation and function

Abstract

Cortical inhibition mediated through GABAergic interneurons plays a critical role in neural circuit functions by shaping neural activity patterns. Interestingly, cortical interneurons have an enormous diversity of cell types in terms of anatomy and physiology. Such cellular diversity has been thought to contribute to increasing a variety of neural circuit functions. However, a lot of fundamental questions concerning development and function of cortical interneuron subtypes have remained to be solved mainly due to lack of reliable methods. In our previous work, we systematically generated Cre knockin mice that target interneuron progenitors and broad subtypes of mature interneurons, which allow us to study many aspects of cortical interneuron subtypes. Using one of mouse lines, we could find that cortical interneurons are produced in the medial ganglionic eminence (MGE) more prolongedly than previously thought. More importantly, we could demonstrate that majority of the latest born interneurons are chandelier cells (ChCs), which have been thought to play a decisive role in neural circuit functions because of their specific innervation of axon initial segments (AISs) (sites of action potential initiation) of excitatory pyramidal neurons. These studies not only discovered the spatial and temporal origin of ChCs but also provided a reliable genetic strategy to dissect different levels of questions. Combining state of the art genetic strategies and microscopy techniques, we are currently studying ChCs as a model to address key issues at different levels. 1) What are molecular mechanisms that are involved in ChC specification? 2) What are cellular and molecular mechanisms that play a role in axonal and synaptic organization of ChCs? 3) What is a role of ChCs in fear memory? These studies will provide our systematic understanding of developmental principles and functional significance of cortical interneuron subtypes. In another project, we are developing a novel genetic method that allows visualization of subtype specific interneuron inputs onto pyramidal neurons. We are aiming to apply this technique to different layers, different subtypes, and different brain areas to gain detailed and systematic pictures of cortical interneuron circuits. This genetic approach may compensate for lack of cell type specificity in contemporary connectomics projects. In this seminar, I will introduce a lot of preliminary data related to above projects and expect to have many questions and discussions from seminar attendees.