353 Eph/Ephrin Signaling Influences Innervation of Outer Hair Cells in Cochlea

OBJECTIVES/GOALS: 48,000,000 people in the U.S. have hearing loss, negatively impacting quality of life and work. Unveiling axon guidance for auditory type II spiral ganglia neurons (SGNs) will aid development of new therapies. I study the role of Eph/Ephrin and planar cell polarity (PCP) signaling during type II SGN turning and outer hair cell (OHC) innervation. METHODS/STUDY POPULATION: This quantitative study was conducted on Efna3 and Vangl2 null mice possessing Neurog1CreERT2 and R26RtdTomato mutations. Spontaneous Cre activity within the Neurogenin1CreERT2 line causes recombination and expression of fluorescent Rosa26 Reporter (R26R)tdTomatoin a restricted number of SGNs, including type IIs. Together, these lines permit SGN sparse labeling. Immunostaining and confocal imaging were used to analyze dsRed in Efna3 and Vangl2 mice and quantify type II SGN turning. In combination, Imaris 3D renderings were used to quantify type II SGN turning, branching, navigation features and temporal effects of EPHRIN-A3-Fc on type IIs via cochlear cultures (a gain-of-function manipulation). For both sexes, 5-6 cochleae per genotype were analyzed and compared by t-test to wildtype (WT) controls. RESULTS/ANTICIPATED RESULTS: Efna3 nulls showed a small rise in type II SGNs incorrectly turning toward the apex at an error rate of 16.0% compared to WTs (n=6; p=0.05). P0 Efna3 nulls had reduced branch number compared to WTs, 4.1 and 7.2, respectively (n=129; p=