Abstract
Purpose: :
To identify miRNAs associated with retinal development and degeneration in dogs affected with XLPRA2 or rcd1, two early-onset canine retinal degenerations caused by, respectively, a microdeletion in RPGRORF15 and a nonsense mutation in PDE6B.
Methods: :
Comparisons between XLPRA2-mutant and normal retinas (3/group/age) were performed using Affymetrix miRNA microarrays. Data were log transformed and normalized with robust multi-array average, and differentially expressed (DE) miRNAs identified with a two-way ANOVA (BH-adjusted p<0.05 and fold change >2). qRT-PCR with TaqMan assays on selected miRNAs was used to confirm microarray data and extend the study to rcd1 dogs. Ct values were normalized with those of miRNA-183, the ratio of mutant vs. control calculated with the DDCt method, and statistical significance verified with an unpaired t-test.
Results: :
Microarray results showed DE miRNAs between 3-7 wks (25 up-/26 down-regulated) and 7-16 wks (1 up-/1 down-regulated) in normal retinas. DE miRNAs were also identified in XLPRA2-mutant compared to normals at 7 (2 up-regulated) and 16 (137 up-/59 down-regulated) wks. qRT-PCR of the pro-apoptotic miR-29b and miR-129 and the anti-apoptotic/pro-survival miR-155, miR-146a and miR-19 confirmed the microarray findings, and revealed very similar patterns of regulation in rcd1-mutant retinas.
Conclusions: :
DE miRNAs were identified during normal development from 3 wks until the retina is mature (7 wks) or fully developed (16 wks). In XLPRA2-mutants little or no expression differences were found at the start (3 wks) or peak (7 wks) of photoreceptor death; during the chronic cell degeneration (16 wks) a significant number of altered miRNAs were identified. Differential regulation of apoptosis-related miRNAs in both mutant retinas indicates that common regulatory processes associated with miRNA function might be involved in the observed retinal degeneration processes and provides interesting opportunities for the development of novel therapies.
Keywords: apoptosis/cell death • gene/expression • retinal degenerations: hereditary