EphA3 and EphA4 regulate ephexin1 and RhoAs GTPases activity during axon growth of retinal ganglion cells

MEDORI, MARA; SPELZINI, GONZALO; TERUEL, LUISA R; SANCHEZ, VIVIANA; SCICOLONE, GABRIEL

Córdoba

Congreso; XXXIII Congreso Anual SAN 2018; 2018

Sociedad Argentina de Investigación en Neurociencia

EPHA3 AND EPHA4 REGULATE EPHEXIN1 AND RHO GTPASES ACTIVITY DURING AXON GROWTH OF RETINAL GANGLION CELLS. EphA3 and EphA4 regulate ephexin1 and Rho GTPases activity during axon growth of retinal ganglion cells. MARA MEDORI1,2, GONZALO SPELZINI1,2, LUISA RENEÉ TERUEL1,2, VIVIANA SANCHEZ1,2, GABRIEL SCICOLONE1,2. 1. CONICET ? Universidad de Buenos Aires, Instituto de Biología Celular y Neurociencias?Prof. E. De Robertis? (IBCN). Ciudad de Buenos Aires, Argentina.2. Universidad de Buenos Aires, Facultad de Medicina, Departamento de Biología Celular, Histología, Embriología y Genética. Ciudad de Buenos Aires, Argentina.The Eph/ephrin system is involved in the chicken retinotectal mapping. We demonstrated that tectal EphA3 stimulates axon growth of nasal retinal ganglion cells (RGCs) toward the caudal tectum preventing them from branching in the rostral tectum. Moreover, we demonstrated that ephrin-A-mediated EphA4 forward signaling decreases the level of axon growth and increases the density of axonal interstitial filopodia of nasal RGCs whereas the tectal EphA3 ectodomain produces the opposite effects by decreasing the EphA4 signaling pathway by competing with EphA4 for ephrin-As binding.Our purpose was to determine whether the EphA4 forward signaling and EphA3 stimulation regulate the activity of Rho GTPases.We cultured chicken embryo retinal explants exposed to control conditions, to the EphA3 ectodomain (EphA3-Fc) or to KYL (EphA4 inhibitor) to evaluate the axon growth and the level of expression and activity of ephexin1 (GEF of Rho GTPases); RhoA and Cdc42. We also performed total homogenates of chicken embryo nasal retinas previously exposed to the same experimental conditions. We evaluated the level of expression and activity of ephexin1, RhoA and Cdc42 by Western blot. The results showed that EphA4 forward signaling decreases axon growth by increasing ephexin1 and RhoA1 activity and decreasing Cdc42 activity; whereas EphA3 ectodomain increases axon growth by decreasing ephrin-A-induced-EphA4 signaling, ephexin1 and RhoA1 activity and increasing Cdc2 activity.Supported by Research Grants: PIP 0441 from CONICET and UBACYT 0526.Key words: axon growth, retinotectal system, Eph/ephrin system, Rho GTPases, chick embryo, development.