miR-183/96 plays a pivotal regulatory role in mouse photoreceptor maturation and maintenance

Abstract

MicroRNAs (miRNAs) are known to be essential for retinal maturation and functionality; however, the role of the most abundant miRNAs, the miR-183/96/182 cluster (miR-183 cluster), in photoreceptor cells remains unclear. Here we demonstrate that ablation of two components of the miR-183 cluster, miR-183 and miR-96, significantly affects photoreceptor maturation and maintenance in mice. Morphologically, early-onset dislocated cone nuclei, shortened outer segments and thinned outer nuclear layers are observed in the miR-183/96 double-knockout (DKO) mice. Abnormal photoreceptor responses, including abolished photopic electroretinography (ERG) responses and compromised scotopic ERG responses, reflect the functional changes in the degenerated retina. We further identify Slc6a6 as the cotarget of miR-183 and miR-96. The expression level of Slc6a6 is significantly higher in the DKO mice than in the wild-type mice. In contrast, Slc6a6 is down-regulated by adenoassociated virus-mediated overexpression of either miR-183 or miR-96 in wild-type mice. Remarkably, both silencing and overexpression of Slc6a6 in the retina are detrimental to the electrophysiological activity of the photoreceptors in response to dim light stimuli. We demonstrate that miR-183/96-mediated fine-tuning of Slc6a6 expression is indispensable for photoreceptor maturation and maintenance, thereby providing insight into the epigenetic regulation of photoreceptors in mice.miR-183/96/182 cluster | regulation | photoreceptor | taurine transporter | degeneration M icroRNAs (miRNAs) are known to act as important epigenetic coordinators during posttranscriptional processing via the regulation of hundreds of target genes with great temporal and spatial precision (1-3). Wholesale and individual disruption of miRNAs has been shown to result in various retinal defects and other sensorial diseases (4-6). The retinal photoreceptor is a type of ciliated neuron in which the miR-183 cluster represents the most highly expressed miRNAs. Although different mouse models have been generated to determine the roles of the miR-183 cluster, many previous studies have used nonspecific or incomplete miRNA depletion to examine the effects of eliminating specific miRNAs on photoreceptor degeneration (5, 6). Little is known about the impact of a "null" miR-183/96/182 model in vivo.A recent study of miR-182 and miR-183 identified these two miRNAs as essential for the maturation and function of cone photoreceptors (7). In addition, their expression is necessary and sufficient for the formation of cone outer segments (OSs) (7). Another study likewise showed that inactivation of the miR-183 cluster by gene trapping resulted in abnormal electroretinography (ERG) responses, progressive synaptic defects, and progressive retinal degeneration (4). Other investigators have reported that impairment of miR-96 resulted in hair cell death in the inner ear, as well as progressive hearing loss in zebrafish, mice, and humans (8-10). Notwithstanding these findings, however, our understanding of the re...

Functional microRNA targetome undergoes degeneration-induced shift in the retina

“…Expectedly, AGO2-loaded miRNA found in both DR and PD groups, comprised miRNAs that are known to play a role in retinal development and homeostasis such as the photoreceptor cluster miR-183/96/182 (Bellon et al, 2017, Busskamp et al, 2014, Fan et al, 2017, Karali et al, 2007, Krol et al, 2010, Lumayag et al, 2013, Xiang et al, 2017, Xu et al, 2007; miR-204-5p (Barbato et al, 2017, Conte et al, 2010, Conte et al, 2015, Karali et al, 2016, let-7a-5p (La Torre et al, 2013) and miR-124-3p (Chu-Tan et al, 2018, Karali et al, 2007, Sanuki et al, 2011, showing consistent overlap with previous studies. However, despite significant changes in differential global miRNA expression in the damaged retina, there were no significant changes in AGO2-loaded miRNA between DR and PD retinas suggesting that the retina appears to be utilising the existing miRNA population in both physiological states.…”

“…Interestingly, miR-124-3p was overwhelmingly expressed in DR retinas, representing approximately 75% of the AGO2-bound miRnome ( Figure 3B). Photoreceptor specific miR-183-5p (part of a cluster miR182/96/183) , Karali et al, 2007, Krol et al, 2010, Xiang et al, 2017, Xu et al, 2007 was the second most abundant miRNA followed by miR-124-5p. The remaining top 10 included miR-125b-5p, miR-125a-5p, miR-181a-5p, miR-191-5p and three members of the miR-29 family: miR-29a-3p; miR-29b-3p; and miR-29c-3p.…”

Functional characterization of CEP250 variant identified in nonsyndromic retinitis pigmentosa

“…To determine whether the Cep250 deficiency could influence retinal function, we subjected the KI mice to ERG at P30, P90, and P180. ERGs were recorded following the protocol as previously described (Xiang et al, ). At the earliest evaluation time point P30, the homozygous KI mice did not show any apparent changes in both scotopic and photopic ERG responses to low light stimulus at intensities‐1.7 log (cd·s/m 2 ) and 0.7 log (cd·s/m 2 ), respectively (Figure a,b).…”

Extracellular vesicles and their miRNA cargo in retinal health and degeneration: mediators of homeostasis, and vehicles for targeted gene therapy

“…Therefore, we attribute the decrease in isolated retinal exosomes to a loss of photoreceptors. In addition, the high abundance of photoreceptor prominent miRNAs miR-124-3p (Chu-Tan, ) and miR-183-5p (Xiang, Chen et al 2017) in isolated retinal exosomes, further attests to a potential photoreceptor origin, with miR-124-3p comprising 17.5% and 16.3% of the total ExoMiRnome in normal and damaged retinas, respectively.…”