Abstract
Rab11a and Rab8a are ubiquitous small GTPases shown as required for rhodopsin transport in Xenopus laevis and zebrafish photoreceptors by dominant negative (dn) disruption of function. Here, we generated retina-specific Rab11a (retRab11a) and Rab8a (retRab8a) single and double knockout mice to explore the consequences in mouse photoreceptors. Rhodopsin and other outer segment (OS) membrane proteins targeted correctly to OS and electroretinogram (ERG) responses in all three mutant mouse lines were indistinguishable from wild-type (WT). Further, AAV (adeno-associated virus)-mediated expression of dnRab11b in retRab11a-/- retina, or expression of dnRab8b in retRab8a-/- retina did not cause OS protein mislocalization. Finally, a retRab8a-/- retina injected at one month of age with AAVs expressing dnRab11a, dnRab11b, dnRab8b, and dnRab10 (four dn viruses on Rab8a-/- background) and harvested three months later exhibited normal OS protein localization. In contrast to results obtained with dnRab GTPases in Xenopus and zebrafish, mouse Rab11a and Rab8a are dispensable for proper rhodopsin and outer segment membrane protein targeting. Absence of phenotype after expression of four dn Rab GTPases in a Rab8a-/- retina suggests that Rab8b and Rab11b paralogs maybe dispensable as well. Our data thus demonstrate significant interspecies variation in photoreceptor membrane protein and rhodopsin trafficking.
Highlights
Mammalian photoreceptors are polarized neurons, each consisting of an outer segment (OS), connecting cilium (CC), inner segment (IS), nucleus and synaptic terminal
In the Rab11a ES cell line, a gene trap (GT) cassette was inserted into intron 1 and exons 2 and 3 are flanked by loxP sites (Fig 1A)
Germline deletion of Rab11a is embryonically lethal as live pups were never born, as published [35]. retRab11a-/- were generated by crossing Rab11afl/fl with transgenic Six3-Cre mice which express Cre in retina starting at embryonic day 9.5 (E9.5)
Summary
Mammalian photoreceptors are polarized neurons, each consisting of an outer segment (OS), connecting cilium (CC), inner segment (IS), nucleus and synaptic terminal. PLOS ONE | DOI:10.1371/journal.pone.0161236 August 16, 2016
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