Short term optical defocus perturbs normal developmental shifts in retina/RPE protein abundance

Abstract

BackgroundMyopia (short-sightedness) affects approximately 1.4 billion people worldwide, and prevalence is increasing. Animal models induced by defocusing lenses show striking similarity with human myopia in terms of morphology and the implicated genetic pathways. Less is known about proteome changes in animals. Thus, the present study aimed to improve understanding of protein pathway responses to lens defocus, with an emphasis on relating expression changes to no lens control development and identifying bidirectional and/or distinct pathways across myopia and hyperopia (long-sightedness) models.ResultsQuantitative label-free proteomics and gene set enrichment analysis (GSEA) were used to examine protein pathway expression in the retina/RPE of chicks following 6 h and 48 h of myopia induction with − 10 dioptre (D) lenses, hyperopia induction with +10D lenses, or normal no lens rearing. Seventy-one pathways linked to cell development and neuronal maturation were differentially enriched between 6 and 48 h in no lens chicks. The majority of these normal developmental changes were disrupted by lens-wear (47 of 71 pathways), however, only 11 pathways displayed distinct expression profiles across the lens conditions. Most notably, negative lens-wear induced up-regulation of proteins involved in ATP-driven ion transport, calcium homeostasis, and GABA signalling between 6 and 48 h, while the same proteins were down-regulated over time in normally developing chicks. Glutamate and bicarbonate/chloride transporters were also down-regulated over time in normally developing chicks, and positive lens-wear inhibited this down-regulation.ConclusionsThe chick retina/RPE proteome undergoes extensive pathway expression shifts during normal development. Most of these pathways are further disrupted by lens-wear. The identified expression patterns suggest close interactions between neurotransmission (as exemplified by increased GABA receptor and synaptic protein expression), cellular ion homeostasis, and associated energy resources during myopia induction. We have also provided novel evidence for changes to SLC-mediated transmembrane transport during hyperopia induction, with potential implications for signalling at the photoreceptor-bipolar synapse. These findings reflect a key role for perturbed neurotransmission and ionic homeostasis in optically-induced refractive errors, and are predicted by our Retinal Ion Driven Efflux (RIDE) model.Electronic supplementary materialThe online version of this article (10.1186/s12861-018-0177-1) contains supplementary material, which is available to authorized users.

Electroretinography and Gene Expression Measures Implicate Phototransduction and Metabolic Shifts in Chick Myopia and Hyperopia Models

“…Most notably, photoreceptor proteins involved in the generation of the electroretinogram response were negatively correlated with refraction across negative and positive lens groups at this early time-point [26]. Furthermore, changes in the expression of ion transporters, including Na/K/ATPase and other ATP-powered pumps, were evident at later time-points, consistent with the expected link between cell activity, ion transport and associated metabolic needs during periods of altered eye growth [25][26][27][28][29]. Concurrent changes in the expression of immune (particularly complement-coagulation) and oxidative stress genes and proteins previously linked to maculopathy and choroidal neovasculatization suggests that downstream signalling cascades during periods of altered growth may combine with structural stress to predispose secondary pathology with age in high myopia [26,27,[29][30][31].…”

“…Gene-level statistics implicated thousands of transcripts during lens-induced myopia induction, but only six transcripts under hyperopia induction conditions. Due to the single-gene focus of the original analysis, it remains unclear whether similar gene pathways are implicated at early time-points in the lens myopia and hyperopia models, as reported in our previous 6 h proteomics [26,28], or in transcriptome measures at later time-points [29,30]. Thus, we re-analysed Stone et al's data using the Gene Set Enrichment Analysis (GSEA) algorithm.…”

RNA-seq and GSEA identifies suppression of ligand-gated chloride efflux channels as the major gene pathway contributing to form deprivation myopia

“…TPMPA) to inhibit the response to FD by inhibiting axial elongation and vitreous chamber depth 16 , 125 – 128 . Downregulation of GABA and glycine in retinal tissue has also been seen in normally growing chicks over a 48 h period 129 , whereas the same study observed an increase in GABA signaling proteins in the same 6–48 h period when chicks wore negative lens wear and during which refractive compensation was achieved 129 .…”

Omics in Myopia

“…Thus, the methods for protein quantification have been used increasingly nowadays, with the most popular being the label-free technique and chemical labeling. The LF method was used, among others, to analyze the vitreous and retina from both humans [10,32] and animals [15,21,27]. In turn, chemical tags found application in the analysis of the proteomic profiles of the retina, vitreous and aqueous humor.…”