Phosphodiesterase 6β Expression In Developing Mouse Retina.

The rd1 mouse is a well-studied model of retinitis pigmentosa (RP), an inherited retinal degenerative disease affecting approximately 1 in 4000 people. It is characterized by a mutation in the Pde6b gene that codes for Phosphodiesterase 6β (PDE6β), a downstream effector of phototransduction. Pde6b gene expression occurs embryonically in mouse retina, whereas other proteins involved in phototransduction are expressed around postnatal day 5 (P5). The primary aim of this study is to investigate the temporal and spatial expression pattern of PDE6β protein during photoreceptor development. Using Western blots with wild type and rd1 mouse retinas from P2 ‐ P21 we demonstrated that PDE6β protein is expressed in wild type retinas by P2 and is not detected in rd1 retinas. The earliest detection of PDE6β in wild type retinas by immunohistochemistry was at P6, where it was confined to the apical region of the photoreceptor layer. The expression of PDE6β protein prior to differentiation of photoreceptor cells and prior to expression of other phototransduction proteins is consistent with the hypothesis that PDE6β may play a role during photoreceptor development distinct from its role in phototransduction. Our lab previously showed that Prenylated Rab Acceptor 1 (PRA1), a vesicular trafficking protein, is downregulated in the developing rd1 retina, although its function in the retina is unknown. The second aim of this study was to explore the relationship between PRA1 and PDE6β. We used immunohistochemistry to determine whether the two proteins are co-localized during the postnatal differentiation period. However, no co-localization between PDE6β and PRA1 was detected. The function of PRA1 in developing retina remains to be elucidated. Abbreviations: cGMP ‐ cyclic guanosine monophosphate; CNG ‐ cyclic nucleotide-gated; Crx ‐ cone-rod homeobox protein; E ‐ embryonic day; ER ‐ endoplasmic reticulum; GFP ‐ green fluorescent protein; IS ‐ inner segment; NDS ‐ normal donkey serum; Nrl ‐ neural retina leucine zipper protein; OCT ‐ Optimal Cutting Temperature; OS ‐ outer segment; P ‐ postnatal day; PBS ‐ phosphate buffered saline; PDE6 ‐ phosphodiesterase 6; PKG ‐ protein kinase G; PRA1 ‐ Prenylated Rab Acceptor 1; RP ‐ Retinitis pigmentosa; Rho ‐ rhodopsin; RPC ‐ retinal progenitor cells