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Xiaoting Mai, Chen Haoyu; Retinal Degeneration in Robo4 knockout mice. Invest. Ophthalmol. Vis. Sci. 2020;61(7):663.
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Endothelium-specific axon-guidance receptor - Robo4 is reported to be expressed in retina, but its role is still unclear. We hypothesize that when Robo4 gene expression is absent, degenerations will occur in the retinal layers, and we verified this by observing the retinal phenotypic characteristics of Robo4 knockout mice.
2-month-old mice were divided into four groups, each group has six mice. Experimental groups: Robo4 knockout mice and HO-Robo4 knockout mice. Control groups: wild-type mice and HO-wild-type mice. (HO- means mice which grew after hyperbaric oxygen induction treatment at 7 days old). The mice eyeballs were taken for paraffin section with HE staining and retinal wholemount with GFAP, Isolectin and DAPI staining. The retinal layer thickness of the non-hyperbaric oxygenation-treated mice was analyzed using the HE staining section. All data were statistically analyzed using Student's t test.
Retinal thickness analysis showed that the average retinal layer thickness of Robo4 knockout mice is thicker in IPL and thinner in other layers, especially in IS/OS. The retinal sections showed photoreceptor degeneration, RPE depigmentation and vacuolar change and abnormal nuclear collection in Robo4 knockout mice. In HO-Robo4 knockout mice, an allosteric phenomenon appeared, characterizing by the retinal nucleus disorder surrounding a granulomatous lesion, accompanied by OPL disappearance, IS/OS atrophy, RPE depigmentation and stratification. The retinal wholemount showed that Robo4 knockout mice had block-like deposits, luminal lesions and intravascular granular deposits, and müller cells package the block-like deposits with atrophic dendrites. The phenomenon were more obvious after hyperbaric oxygen induction, and müller cells appeared with a large number of scar nodules.
Multiple degeneration occurs in the retina of Robo4 knockout mice, and will be more obvious after oxidative stress, including retinal thickness change, photoreceptor atrophy degeneration, RPE depigmentation and stratification change and retinal cells allosteric phenomenon. Retinal cells allosteric phenomenon may be associated with the degeneration of müller cells and the change of its secretion factors. Further mechanistic studies are needed to better elucidate Robo4's function on the retina.
This is a 2020 ARVO Annual Meeting abstract.
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