Peter D. Lukasiewicz - US grants

DESCRIPTION (provided by applicant): This project addresses a basic research priority of the NEI, how do adaptational changes in retinal networks affect visual processing. The retina responds to light intensities that vary over a billion-fold, but individual retinal neurons can onl vary their output 100-fold. To overcome this disparity between input and output, retinal neurons adapt to background illumination by shifting their response ranges to span ambient illumination intensities. Adaptation occurs within photoreceptors and also at post-receptor locations in the retina. In this proposal we will study two forms of post-receptor adaptation. Using electrophysiological, pharmacological and anatomical approaches, we will investigate the retinal circuits that 1) control the transition from rod to cone signaling and 2) control the variation of center-surround spatial processing at different ambient light levels. A critical feature of the transition from rod- to cone-mediated vision is to suppress rod signaling and enhance cone signaling. Despite extensive study, the circuits responsible for this transition are poorly understood. We discovered a novel form of inhibition that suppresses the function of a critical signaling element, the rod bipolar cell, when it is activated by bright light. In aim 1, we determie whether this novel form of inhibition in rod bipolar cells contributes to the transition from rod t cone vision. Changes in the level of ambient illumination produce post-receptor adaptation that alters center-surround spatial processing. This form of spatial processing is critical for the detection of edges and spatial contrast. The circuits that mediate this form of post-receptor adaptation are unknown. In aim 2, we determine the circuits and synaptic mechanisms that produce the adaptational changes in center-surround spatial processing caused by different ambient light levels.

The Electronics Core Services Module (ECSM) provides services in the fabrication of new devices as well as in diagnosis and repair of existing equipment. For instruments or devices not commercially available or adaptable, the ECSM will work with core investigators to design, modify and fabricate electronic devices that are required for a given experimental approach. For the most part, these involve electronic devices required for neurophysiological studies. Another key service provided by the ECSM is the diagnosis and repair of laboratory equipment. Many times repair services are needed on an emergency basis, and the core engineer is able to respond to an outage in a matter of hours to diagnose and/or repair the instrument and return it to service. The ECSM is housed in a recently renovated shop dedicated for exclusive use of the module engineer and equipped with all the necessary electronic meters and hand tools. Access to the ECSM enhances the environment for conducting quality research by allowing core scientists to push the limits of technology in attempts to address new ideas and approaches to vision science problems that have not before been solved.

DESCRIPTION (provided by applicant): Inhibition is an essential element in retinal information processing. Lateral, inhibitory pathways in the outer and inner plexiform layers modulate the flow of visual information between photoreceptors and bipolar cells, and bipolar cells and ganglion cells, respectively. In mammalian retina, the precise roles of the two lateral pathways are not well understood. GABA (gamma-aminobutyric acid) is an important mediator of inhibition in the retina, and other parts of the CNS. The retina is unique in that two classes of ionotropic GABA receptors, GABAa and GABAc mediate inhibitory signals. These receptors have been shown to have distinct functional properties and cellular distributions in the retina. GABAc receptors, which are found mainly in the retina, mediate longer lasting responses and are more sensitive to GABA than GABAa receptors. GABAa receptors are found on all retinal neurons, whereas GABAc receptors are located mainly on bipolar cell axon terminals and, to a less extent, in the outer plexiform layer (OPL). The goal of the proposed work is to determine how these two classes of GABA receptors participate in the shaping of the visual signal in the mammalian retina. The precise functional roles of GABA receptors in the mammalian retina are unknown. At the inner plexiform layer, GABA is an essential signal for modulating the spatial and temporal aspects of visual information processing. However, it is not known how these inhibitory signals are parsed out by functionally different GABAa and GABAc receptors. Using an animal that lacks GABAc receptors, the GABArho1 null mouse, we will determine the roles of GABAa and GABAc receptors in signal processing in the inner and outer plexiform layers. The proposed research consists of two aims. Aim1 will determine how GABAa and GABAc receptors modulate responses in bipolar cells, which are the first cells that divide the visual signal into distinct channels. Aim 2 will determine how the two classes of GABA receptors give rise to the diversity of spatial and temporal processing at the inner plexiform layer. This aim will also evaluate the relative roles of inner and outer lateral inhibition in shaping ganglion cell responses, the output signals of the retina.

? DESCRIPTION (provided by applicant): A wide-ranging program has been designed to train pre-and postdoctoral scientists in the broad area of vision science. Trainees participate in graduate and postdoctoral programs in Biochemistry, Computational & Molecular Biophysics, Computational & Systems Biology, Developmental, Regenerative & Stem Cell Biology, Human and Statistical Genetics, Immunology, Molecular Cell Biology, Molecular Genetics and Genomics, Molecular Microbiology & Microbial Pathogenesis, and Neurosciences. The training program will be delivered by 33 preceptors, 14 of whom are NEI funded, studying nearly all aspects of visual function and pathology. Predoctoral trainees will take courses that provide detailed information about the neurobiology of the visual system and/or a comprehensive course in all aspects of the development, physiology and pathology of the eye. Postdoctoral trainees are also encouraged to attend these courses. Pre- and postdoctoral trainees are strongly encouraged to participate in the rich environment of seminars, advanced courses, honorary lectures, journal clubs, and retreats offered in the Division of Biology and Biomedical Sciences at Washington University and in the NEI-sponsored course, Fundamental Issues in Vision Research. Many of these opportunities involve the participation of both basic and clinical scientists, assuring that trainees will learn about the origins and treatment of human ocular/visual system diseases. The training program supports two postdoctoral trainees for their first year at Washington University. This provides adequate time for them to apply for individual research training grant support. The predoctoral training program supports 6 graduate students. This assures that an adequate number of vision science trainees are available to enrich the training environment. The faculty members in the training program currently have 41 predoctoral and 37 postdoctoral trainees in their laboratories. This demonstrates the commitment of the faculty to training and illustrates the large size of the pool of applicants from which the trainin grant can draw. The overall goal of this program is to identify the most promising scientists and to provide them with a training environment that maximizes the probability that they will become productive contributors to the understanding and treatment of human ocular and visual system diseases. RELEVANCE: Talented and well-trained scientists are essential for continued progress in vision research. The goal of this program is to select the best scientists from the large pool of graduate, MD/PhD candidates and postdoctoral fellows at Washington University and provide training that will prepare them to lead future research in vision.

Project Summary The objective of this application is to provide established NEI-funded researchers with additional, shared support to enhance their individual research capabilities. A further goal is to enhance the research capability of Washington University by fostering collaborative studies and attracting scientists new to vision research. These objectives will be achieved by operating four research/service cores, which will provide the following services. 1. A Morphology and Imaging Core will provide technical support in the preparation of ocular tissues for analysis by light or electron microscopy. The core also provides in situ hybridization, immunocytochemistry and laser micro-dissection. Core investigators have unlimited access to confocal and multiphoton microscopes. For in vivo imaging/measurements, a fluorotron, fluorescence macroscope, and small animal Optical Coherence Tomography (OCT) system are available. 2. A Visual Function Testing Core will provide expertise, instrumentation, and training on technologies used to quantify visual performance in mice and other model systems. ERG, VEP and optometry analysis are supported. This core also includes technical support for the fabrication, diagnosis and repair of electronic equipment. 3. A Biostatistics Core will provide statistical and methodological expertise in study design and assure the validity of statistical analyses and reported results. This core will also assist in the training of residents and clinicians in areas of clinical research methodology. 4. A Molecular Genetics Core will provide customized services for the production of transgenic and knockout mice using Crispr/Cas9 technology. Supported services also include assistance with design and preparation of constructs for gene targeting, preparation of DNA clones and probes, design of polymerase chain reaction components, microinjection services (IVF), and sperm/embryo cryopreservation. Provision of these support services and resources will greatly enhance the research capabilities of investigators at Washington University and will facilitate collaboration among new and established vision scientists.