RhoB is Essential in Retinal Function and Normal Intraocular Pressure

Purpose : RhoB is a small GTPase with a role in apoptosis, intracellular transport and angiogenesis as studied in cancer, diabetes, and retinopathy of prematurity. The lack of RhoB GTPase and how it affects the normal and stressed retina has not been extensively studied. Previous studies on the critical period have shown that supplemental oxygen during the critical period decreased photoreceptor death in the retina while hypoxic conditions increased photoreceptor death. Therefore, we investigated how RhoB-/- mice's retina neurons would react to oxygen changes during the critical period of retinal development and how aging affects these retinas. Methods : RhoB null mice (C57BI/6JR hoBV-or RhoB-/-) and control C57bl/6J (C57) mice were used in this study. Mice were placed into a chamber that allowed for different oxygen concentrations at 16%O2 (hypoxia), 21 %O2 (normoxia), or 75%O2 (hyperoxia) from Postnatal day 7 (P7) to P20. Immunofluorescence was conducted at P12, P16, P28 and 1 year to quantify the number of apoptotic cells. Retinal thickness was assessed in three layers of the retina, outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer (GCL) at P28 and 1 year. Electroretinography (ERG) were conducted at P27 and 1 year. Lastly, intraocular pressure (IOP) was measured using a tonopen in aging animals. Results : Young RhoB-/- exhibited significantly increased cell death in the ONL, INL and GCL at 21 %O2 when compared to control mice in the early critical period (P12). At 4 weeks, RhoB-/- mice displayed significantly more GCL death compared to C57 in all varying oxygen conditions (p