Vision begins when light is converted to an electrical signal in the photoreceptors. Increases in light decrease release of the neurotransmitter, glutamate, from cone and rod photoreceptor terminals, and decreases in light increase its release. These changes in synaptic glutamate concentration are detected by two classes of bipolar cells that then transmit the signal vertically through the retinal circuit to the ganglion cells. The neurotransmitter changes also are detected by horizontal cells that provide lateral transmission in the form of feedback and feedforward inhibition. There are two classes of bipolar cells, hyperpolarizing (HBCs) and depolarizing (DBCs). HBCs utilize ionotropic glutamate receptors and hyperpolarize in response to a light flash. DBCs utilize a metabotropic glutamate receptor, mGluR6, that signals to TRPM1, depolarizing in response to a light flash. Defects in transmission in DBCs results in complete congenital stationary night blindness (cCSNB). Mutations in GRM6, NYX, TRPM1, GPR179 and LRIT3 cause cCSNB. The mechanism by which mGluR6 signals TRPM1 is largely unknown. The long term goal of this project is study the molecular interactions between LRIT3 and known and known components DBC signal transduction components.
The specific aims are: 1) determine the function of LRIT3 domains on rod and cone DBC mGluR6 signalplex assembly and signaling, and 2) Define protein interactions required for DBC assembly and synaptic function, and 3) determine the function of LRFN1 and 2 on cone synapse function. At the completion of this project, we will have characterized the function of LRIT3 and how it interacts with currently unknown presynaptic partners. Further, we will have identified new candidate genes for congenital stationary night blindness.
Vision requires a light signal be converted to an electrical signal, which is then transmitted to the brain via a neuronal network. The diseases being studied are referred to as congenital stationary night blindness. The studies in this proposal will characterize the nature of the defects and determine the function of newly identified proteins critical for normal vision, which will set the stage of therapeutic approaches in the future.
|Peachey, Neal S; Hasan, Nazarul; FitzMaurice, Bernard et al. (2017) A missense mutation in Grm6 reduces but does not eliminate mGluR6 expression or rod depolarizing bipolar cell function. J Neurophysiol 118:845-854|
|Sarria, Ignacio; Orlandi, Cesare; McCall, Maureen A et al. (2016) Intermolecular Interaction between Anchoring Subunits Specify Subcellular Targeting and Function of RGS Proteins in Retina ON-Bipolar Neurons. J Neurosci 36:2915-25|
|Scalabrino, Miranda L; Boye, Sanford L; Fransen, Kathryn M H et al. (2015) Intravitreal delivery of a novel AAV vector targets ON bipolar cells and restores visual function in a mouse model of complete congenital stationary night blindness. Hum Mol Genet 24:6229-39|
|Qian, Haohua; Ji, Rui; Gregg, Ronald G et al. (2015) Identification of a new mutant allele, Grm6(nob7), for complete congenital stationary night blindness. Vis Neurosci 32:E004|
|Ray, Thomas A; Heath, Kathryn M; Hasan, Nazarul et al. (2014) GPR179 is required for high sensitivity of the mGluR6 signaling cascade in depolarizing bipolar cells. J Neurosci 34:6334-43|
|Klooster, Jan; van Genderen, Maria M; Yu, Minzhong et al. (2013) Ultrastructural localization of GPR179 and the impact of mutant forms on retinal function in CSNB1 patients and a mouse model. Invest Ophthalmol Vis Sci 54:6973-81|
|Balmer, Jasmin; Ji, Rui; Ray, Thomas A et al. (2013) Presence of the Gpr179(nob5) allele in a C3H-derived transgenic mouse. Mol Vis 19:2615-25|
|Orlandi, Cesare; Posokhova, Ekaterina; Masuho, Ikuo et al. (2012) GPR158/179 regulate G protein signaling by controlling localization and activity of the RGS7 complexes. J Cell Biol 197:711-9|
|Peachey, Neal S; Ray, Thomas A; Florijn, Ralph et al. (2012) GPR179 is required for depolarizing bipolar cell function and is mutated in autosomal-recessive complete congenital stationary night blindness. Am J Hum Genet 90:331-9|
|Peachey, Neal S; Pearring, Jillian N; Bojang Jr, Pasano et al. (2012) Depolarizing bipolar cell dysfunction due to a Trpm1 point mutation. J Neurophysiol 108:2442-51|
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