DOWNREGULATION OF SPLICING REGULATOR RBFOX1 COMPROMISES VISUAL DEPTH PERCEPTION

Rbfox1 is a splicing regulator that has been associated with various neurological conditions such as autism spectrum disorder, mental retardation, epilepsy, attention-deficit/hyperactivity disorder, and schizophrenia. We show that in adult rodent retinas, Rbfox1 is expressed in all types of retinal ganglion cells (RGCs) as well as in certain subsets of amacrine cells (ACs) within the inner nuclear and ganglion cell layers. In developing retinas, Rbfox1 can be detected as early as E12. At that age, Rbfox1 is localized in the cytoplasm of differentiated RGCs. Between P0 and P5, strong expression of Rbfox1 in the inner plexiform layer was observed. This coincided with switching of Rbfox1 localization in RGC somas from cytoplasmic to a predominantly nuclear. Dynamic changes in Rbfox1 expression during first 10 postnatal days are correlated with the stage II spontaneous retinal waves of excitation, which in mice begins around the time of birth and continues for as long as two weeks. By P10, dendritic staining of Rbfox1 was dramatically reduced and remained so in the fully developed retina. In Rbfox1 knockout (KO) animals no detectable changes in retinal gross morphology were observed two months after Rbfox1 downregulation. However, the visual cliff test revealed marked abnormalities of depth perception of these animals. Retinal transcriptome analysis of Rbfox1 KO mice identified a number of genes that are involved in establishing neural circuits and synaptic transmission, including Vamp1, Vamp2, Snap25, Trak2, and Slc1A7, suggesting a role of Rbfox1 in the regulation of genes that facilitate AC and RGC synaptic communication. Retinal RNRetinal RNA-seq analysis was performed with 3 biological replicates representing Rbfox1-/- and 3 biological replicates representing control animals to identify differentially expressed and alternatively spliced genes. Rbfox1-/- animals were generated by crossing Rbfox1loxP/loxP(B6.129S2-Rbfox1tm1.1Dblk/J) mice with Tg(UBC-cre/ERT2)1Ejb mice. Cre expression was induced with tamoxifen in adult homozygous Rbfox1loxP/loxP; UBC-Cre+/- mice. Mice used in this study were maintained on the C57BL/6J background.