Dicer Inactivation Leads to Progressive Functional and Structural Degeneration of the Mouse Retina

157

183

MicroRNAs (miRNAs) are small noncoding RNAs that have important roles in the regulation of gene expression. The roles of individual miRNAs in controlling vertebrate eye development remain, however, largely unexplored. Here, we show that a single miRNA, miR-204, regulates multiple aspects of eye development in the medaka fish (Oryzias latipes). Morpholino-mediated ablation of miR-204 expression resulted in an eye phenotype characterized by microphthalmia, abnormal lens formation, and altered dorsoventral (D-V) patterning of the retina, which is associated with optic fissure coloboma. Using a variety of in vivo and in vitro approaches, we identified the transcription factor Meis2 as one of the main targets of miR-204 function. We show that, together with altered regulation of the Pax6 pathway, the abnormally elevated levels of Meis2 resulting from miR-204 inactivation are largely responsible for the observed phenotype. These data provide an example of how a specific miRNA can regulate multiple events in eye formation; at the same time, they uncover an as yet unreported function of Meis2 in the specification of D-V patterning of the retina.microRNA | eye development | medaka fish

Section: Mir-204 Controls Lens Differentiation By Targeting Meis2 Andmentioning

confidence: 99%

miR-204 is required for lens and retinal development via Meis2 targeting

Conte

Carrella²,

Avellino³

et al. 2010

157

183

“…7 A-D, F, H, and I). Local signs of focal rearrangements (i.e., formation of rosettes, a common finding in retinal reorganization) or signs of glial reactivity in Muller cells and astrocytes, also frequently reported in a variety of mutants and KO mice (27) were absolutely undetected in the strains under use.…”

Section: Effect Of Melatonin Injection On the Photopic Ergsmentioning

confidence: 99%

“…Details about the procedures used for in situ hybridization and ICCH are described in detail in published work (26,27). For additional details, see SI Methods and Table S1.…”

Section: In Situ Hybridization and Immunocytochemistry (Icch)mentioning

confidence: 99%

Melatonin modulates visual function and cell viability in the mouse retina via the MT1 melatonin receptor

Baba

Pozdeyev²,

Mazzoni³

et al. 2009

113

165

A clear demonstration of the role of melatonin and its receptors in specific retinal functions is lacking. The present study investigated the distribution of MT1 receptors within the retina, and the scotopic and photopic electroretinograms (ERG) and retinal morphology in wildtype (WT) and MT1 receptor-deficient mice. MT1 receptor transcripts were localized in photoreceptor cells and in some inner retinal neurons. A diurnal rhythm in the dark-adapted ERG responses was observed in WT mice, with higher a-and b-wave amplitudes at night, but this rhythm was absent in mice lacking MT1 receptors. Injection of melatonin during the day decreased the scotopic response threshold and the amplitude of the a-and b-waves in the WT mice, but not in the MT1 ؊/؊ mice. The effects of MT1 receptor deficiency on retinal morphology was investigated at three different ages (3, 12, and 18 months). No differences between MT1 ؊/؊ and WT mice were observed at 3 months of age, whereas at 12 months MT1 ؊/؊ mice have a significant reduction in the number of photoreceptor nuclei in the outer nuclear layer compared with WT controls. No differences were observed in the number of cells in inner nuclear layer or in ganglion cells at 12 months of age. At 18 months, the loss of photoreceptor nuclei in the outer nuclear layer was further accentuated and the number of ganglion cells was also significantly lower than that of controls. These data demonstrate the functional significance of melatonin and MT1 receptors in the mammalian retina and create the basis for future studies on the therapeutic use of melatonin in retinal degeneration.electroretinogram ͉ neuroprotection ͉ visual sensitivity ͉ glaucoma

“…Their importance in regulating gene expression in retinal cells is highlighted by the high number of miRNAs that are preferentially expressed in the vertebrate retina (2)(3)(4)(5). Evidence indicates that miRNAs are important for the development and maintenance of correct function within the eye, and in particular the retina (6)(7)(8).…”

mentioning

confidence: 99%

MiR-204 is responsible for inherited retinal dystrophy associated with ocular coloboma

Conte

Hadfield

Barbato

et al. 2015

100

111

Ocular developmental disorders, including the group classified as microphthalmia, anophthalmia, and coloboma (MAC) and inherited retinal dystrophies, collectively represent leading causes of hereditary blindness. Characterized by extreme genetic and clinical heterogeneity, the separate groups share many common genetic causes, in particular relating to pathways controlling retinal and retinal pigment epithelial maintenance. To understand these shared pathways and delineate the overlap between these groups, we investigated the genetic cause of an autosomal dominantly inherited condition of retinal dystrophy and bilateral coloboma, present in varying degrees in a large, five-generation family. By linkage analysis and exome sequencing, we identified a previously undescribed heterozygous mutation, n.37C > T, in the seed region of microRNA-204 (miR-204), which segregates with the disease in all affected individuals. We demonstrated that this mutation determines significant alterations of miR-204 targeting capabilities via in vitro assays, including transcriptome analysis. In vivo injection, in medaka fish (Oryzias latipes), of the mutated miR-204 caused a phenotype consistent with that observed in the family, including photoreceptor alterations with reduced numbers of both cones and rods as a result of increased apoptosis, thereby confirming the pathogenic effect of the n.37C > T mutation. Finally, knockdown assays in medaka fish demonstrated that miR-204 is necessary for normal photoreceptor function. Overall, these data highlight the importance of miR-204 in the regulation of ocular development and maintenance and provide the first evidence, to our knowledge, of its contribution to eye disease, likely through a gain-of-function mechanism.