Events

OFHEC Hearing Research Seminar

L-C. Huang, PR Thorne, GD Housley, JM Montgomery.

During development the auditory nerve grows into the developing cochlea to synapse with the sensory cells and thus provide the right connections with the brain.   Before the onset of hearing the innervation of the developing cochlea undergoes dramatic changes.  We have recently shown that the primary auditory neurones exhibit precisely timed remodelling involving growth to innervate the most of the sensory cells and then a period of refinement before excess nerves are removed by synapse elimination. As a result the mature innervation pattern is established by selective pruning of a subpopulation of synapses. However, the mechanisms driving this process of synapse remodelling are not known. We have examined the expression of synaptic proteins prior to and during synapse elimination in the cochlea of the mouse and have found that the molecular makeup of hair cell synapses changes dramatically during this remodelling phase. Presynaptic neurotransmitter release machinery is selectively reduced in synapses destined for elimination and this correlated with postsynaptic receptor expression. Synapses destined to become permanent hair cell synapses displayed unique synaptic protein expression profiles. These data show that synaptic fate, ie whether a synapse persists or is eliminated, is associated both with synaptic strength and the expression of specific postsynaptic scaffolding proteins.  Understanding the mechanisms that drive formation of permanent synapses has considerable implications for understanding the normal development of the auditory system in humans.

Dr. Johanna Montgomery is a Senior Lecturer in Neuroscience and Principal Investigator of the ‘Synaptic Function Research Group’ at The Centre for Brain Research at The University of Auckland. Her primary research focus is in understanding how brain cells communicate with each other in the developing and the diseased brain. Her PhD was conducted at The University of Otago followed by 6 years of postdoctoral research at Stanford University. She returned to New Zealand and established her independent laboratory in mid-2004. Shortly after this she began collaborating with Prof Housley and Thorne examining the development of the innervation of the cochlea and she will talk about this exciting research today.