Résumé
Purpose : Mutations in IMPG1 and IMPG2 are cause of retinitis pigmentosa (RP) and vitelliform macular dystrophy (VMD). The protein products of these paralog genes are two major components of the interphotoreceptor matrix (IPM). We knocked down the expression of Impg1 or/and Impg2 in medaka fish (Oryzias latipes) model to explore the pathophysiology of retinal dystrophies.Methods : Two transgenic medaka fish lines with fluorescently labeled photoreceptors (Rho:eGFP or TαC:eGFP) were injected with control or Impg1 or/and Impg2 morpholino into one-cell stage fertilized embryos to generate transient knockdowns. At ten days post-fertilization, embryos were cryostat-sectioned and retinas were analyzed by immunofluorescence using confocal microscopy. The length of the outer and inner segments of the photoreceptors was measured using the imageJ software.Results : In the medaka larvae injected with Impg1 and Impg2 morpholino but not with the control, a decreased of inner and outer segment length of rods and a completely absence of outer and inner-segments of cones was observed. The morpholino-induced photoreceptor size defect was identical for both Impg1 and Impg2 morpholino. In addition, there is no cumulative effect with more severe defect obtained by co-injection of the two morpholinos.Conclusions : Together, our data suggest that Impg1 and Impg2 knock down results in abnormal development of the retina in medaka fish. Loss of two major protein functions of the interphotoreceptor matrix results in shorter rod photoreceptors and an absence of cones outer segment in the larvae retina.