The goal of this co-principal investigator, interdisciplinary proposal is to develop techniques for the comprehensive functional characterization of retinal ganglion cell (RGC) types in the mouse retina, and to combine this characterization with mouse transgenic technology in order to determine the relationships between the morphology and physiology of RGC types. Our experiments take advantage of novel multi- electrode array (MEA) recording systems built in the Litke lab. These systems contain over 500 electrodes and can simultaneously record the activity from hundreds of neurons in an intact retina;this represents a 10 fold better yield over currently available technology. We find that this increase in yield is critical for unambiguous functional classification and reliable characterization of the many RGC types in the retina. Furthermore, we hypothesize that the detailed information provided by these MEA systems will make it possible to match the physiologically identified neurons to optically imaged RGCs. Such a match will create a link between function and structure in an unprecedented manner. We have two main aims to accomplish our goals. In the first aim we propose to use two types of large- scale MEAs, a 512-electrode array with 605m interelectrode spacing, and a high density 519-electrode array with 305m spacing, to characterize the receptive field and mosaic properties of RGC types of wild type mice. We have chosen to use these arrays to characterize RGC types in mice because the mouse retina has become an important model to study the role various genes/molecules play in the development of retinal circuitry. The mouse also serves as a model for studying the progression of retinal-degenerative diseases such as glaucoma. In the second aim we plan to use the large-scale MEA technology to correlate the morphological RGC types to their functional counterparts. In addition to being classified using physiological criteria, RGCs are classified using morphological criteria. However, only in rare circumstances can cells be classified by both morphological and physiological properties. Experiments proposed in this aim are designed to correlate morphologically labeled cells with their physiological properties. We will do this by matching the morphological images of GFP marked RGCs with their electrophysiological images and receptive fields. (As described in section c, the electrophysiological image is a technique, developed by the Litke lab, for imaging the spatiotemporal pattern of electrical activity generated by individual neurons.). The purpose of this grant is to obtain a comprehensive characterization of retinal ganglion cell (RGC) types in the mouse retina. This knowledge is essential in order to understand how various molecular and environmental perturbations affect the retina's development and function. Vision is a crucial component of human perception and blindness is a devastating affliction. Understanding what the retinal circuits are is the first step toward understanding how they develop and is also essential to better understand the progression of retinal degenerative diseases (Are specific circuits differentially affected in disease?). In the last 10-20 years, modern molecular techniques, in combination with powerful advances in imaging and electrophysiology, have led to an increase in the use of the mouse as a model system for studying retinal circuitry. It is likely that the knowledge obtained from experiments proposed here will be essential to all who use the mouse visual system as a model.
The first aim of this project is to develop techniques for the classification and functional characterization of retinal ganglion cell (RGC) types in the mouse retina.
The second aim i s to combine this characterization with mouse transgenic technology in order to determine the relationship between the morphology and physiology of RGC types. Upon completion of the proposed aims, we will be in a strong position to use these techniques to determine how various genetic, activity-related, and disease perturbations affect and control the development of neural circuits. This will build a solid foundation for future work aimed at developing therapies for treating retinal damage due to injury or disease.
