Seminar: Mapping the distribution of synapses along dendritic trees by Professor Juan Burrone, Professor of Development Neurophysiology, Department of Developmental Neurobiology, King's College London
Abstract: Neurons in the brain have extensive dendritic arbours that receive both excitatory and inhibitory inputs all along it. The transformation of all these inputs to an output in a single neuron occurs through the integration of synaptic events and the generation of an action potential (or spike) at the axon. The contribution that a single synapse makes to spike output will vary according to its strength and its location on a neuronal arbour. Describing how synapses are distributed across a neuron is therefore crucial for understanding how neurons integrate their synaptic inputs and how they function within a circuit. Providing such a description is a formidable challenge however- a single pyramidal neuron in the mammalian hippocampus, for example, can receive tens of thousands of excitatory and inhibitory inputs. Here, we employ multiple techniques (electrophysiology, serial block face scanning electron microscopy, single and multi-photon microscopy) to begin to map the structure and function of synaptic inputs along the dendrites of pyramidal neurons in area CA1 of the hippocampus. We find that both the presynaptic and postsynaptic compartments of excitatory synapses are distributed in a distance-dependent manner along the basal dendrites of pyramidal cells. This distribution has important consequences for how neurons integrate inputs that arrive at different dendritic locations. In addition, we are now also employing new approaches to establish how GABAergic inhibitory inputs are distributed along these same dendrites. Despite the fact that they are fewer in number, GABAergic inhibition plays a central role in shaping dendritic integration and neuronal output. Indeed, the balance between the overall levels of excitation and inhibition received by a given neuron in the cortex is tightly controlled, a feature that is thought to be crucial in maintaining the stability of cortical networks. We present data suggesting that the balance between excitation and inhibition may extend to subcellular compartments, allowing dendrites to integrate inputs locally and stably.
Biography: Professor Juan Burrone graduated from the University of Bristol, UK, in 1995 with a BSc in Biochemistry. He then obtained a PhD from Cambridge University in 2000,
having worked under the supervision of Prof. Leon Lagnado at the MRC Laboratory of Molecular Biology (LMB). He then moved to the Molecular and Cellular Biology department at Harvard University, USA, to join Prof. Venkatesh Murthy’s lab as a postdoctoral fellow. In 2006 he joined the MRC Centre for Developmental Neurobiology where he is currently a Professor.
He has received many recognitions and awards, including a NARSAD Young Investigator Award (2000); Grable investigator of NARSAD (2001); Wellcome Value in People (VIP) award (2005); Lister Institute Prize winner (2009); Wellcome Trust Young Investigator award (2011); ERC Young Investigator award (2011).