Ectopic synaptic ribbons in dendrites of mouse retinal ON- and OFF-bipolar cells

The ectopic distribution of synaptic ribbons in dendrites of mouse retinal bipolar cells was examined by using genetic ablation of metabotropic glutamate receptor subtype 6 (mGluR6), electron microscopy, and immunocytochemistry. Ectopic ribbons were observed in dendrites of rod and ON-cone bipolar cells in the mGluR6-deficient mouse but not in those of wild-type mice. The number of rod spherules facing the ectopic ribbons in mGluR6-deficient rod bipolar dendrites increased gradually during early growth and reached a plateau level of about 20% at 12 weeks. These ectopic ribbons were immunopositive for RIBEYE, a ribbon-specific protein, but the associated vesicles were immunonegative for synaptophysin, a synaptic-vesicle-specific protein. The presence of ectopic ribbons was correlated with an increase in the roundness of the invaginating dendrites of the rod bipolar cells. We further confirmed ectopic ribbons in dendrites of OFF-cone bipolar cells in wild-type retinas. Of the four types of OFF-cone bipolar cells (T1–T4), only the T2-type, which had a greater number of synaptic ribbons at the axon terminal and a thicker axon cylinder than the other types, had ectopic ribbons. Light-adapted experiments revealed that, in wild-type mice under enhanced-light adaptation (considered similar to the mGluR6-deficient state), the roundness in the invaginating dendrites and axon terminals of rod bipolar cells increased, but no ectopic ribbons were detected. Based on these findings and known mechanisms for neurotransmitter release and protein trafficking, the possible mechanisms underlying the ectopic ribbons are discussed on the basis of intracellular transport for the replenishment of synaptic proteins

Microcircuits for Night Vision in Mouse Retina

electron microscopy Until recently, the anatomical connections of mammalian photoreceptors seemed well understood. Cones and rods were known to form chemical synapses on separate classes of bipolar cell (for review, see Vaney et al., 1991; Sterling, 1998; Boycott and Wassle, 1999; Sharpe and Stockman, 1999). Cone bipolar cells synapse directly on ganglion cells and serve high-light levels (daylight), whereas rod bipolar cells connect to ganglion cells only indirectly via an interneuron and serve low-light levels (starlight). Rods were also known to form electrical synapses with cones and thus to obtain indirect access to the cone bipolar circuits under medium-light levels (twilight). These parallel circuits, identified and quantified in cat (Kolb and Famiglietti, 1974; Kolb, 1977; Sterling et al., 1988), rabbit (Strettoi et al., 1990; Young and Vaney, 1991), and primate (Mills and Massey, 1995), have been considered f undamental to the mammalian design and different from the design

Novel form of miR-29b suppresses bleomycin-induced pulmonary fibrosis.

MicroRNA 29b (miR-29b) replacement therapy is effective for suppressing fibrosis in a mouse model. However, to develop clinical applications for miRNA mimics, the side effects of nucleic acid drugs have to be addressed. In this study, we focused on miRNA mimics in order to develop therapies for idiopathic pulmonary fibrosis. We developed a single-stranded RNA, termed "miR-29b Psh-match," that has a unique structure to avoid problems associated with the therapeutic uses of miRNAs. A comparison of miR-29b Psh-match and double-stranded one, termed "miR-29b mimic" indicated that the single-stranded form was significantly effective towards fibrosis according to both in vivo and in vitro experiments. This novel form of miR-29b may become the foundation for developing an effective therapeutic drug for pulmonary fibrosis

miR-29b protects fibrotic responses in NIH/3T3 cells induced with TGF-β without activating TLRs.

<p>(A) <i>Col1a1</i> mRNA expression in NIH/3T3 cells was reduced after transfection with miR-29b Psh-match compared with cells treated only with TGF-β. The degree of reduction in <i>COL1A1</i> expression induced by miR-29b Psh-match transfection was greater than that induced by either miR-29b scrambled control or miR-29b mimic (Fig 2A) (*P<0.05). (B) miR-29b Psh-match does not induce TLR signaling activity. TLR signaling activity was measured using an NF-κB reporter in which luciferase cDNA was placed under the control of the κB response element. The dsRNA and ssRNA induce the activation of NF-κB through TLR3 and TLR7, respectively.</p

miR-29b Psh-match suppresses pulmonary fibrosis in mice to a greater degree than miR-29b mimic.

<p>(A) In bleomycin-induced pulmonary fibroblast model mice, quantitative real-time PCR data indicates an increase in <i>Col1a1</i> mRNA expression. Expression of <i>Col1a1</i> decreased in the lungs of mice administered with miR-29b Psh-match relative to mice administered with either PBS, miR-29b scrambled control, or miR-29b mimic (*P<0.05). (B) HE and Masson’s trichrome staining showed the pronounced diffuse fibrosis on the lungs in the bleomycin-treated mice. Administration of miR-29b Psh-match suppressed pulmonary fibrosis in an established mouse model of bleomycin-induced pulmonary fibrosis (*P<0.05). High magnification images of the lungs of mice administered with either miR-29b mimic or Psh-match mice are shown in the frames. (C) Hydroxyproline content was measured as micrograms of hydroxyproline per weight in grams of the left lung’s tissues in mice.</p

Bleomycin-induced pulmonary fibrosis in mouse lungs.

<p>(A) Images of lungs from mice that were either subject to nasal administration of methylene blue (right) or not (left). (B) Fold changes in <i>Col1a1</i> mRNA showed a peak one week after bleomycin administration. (*P<0.05) (C) Histological staining by HE and Masson’s trichrome showed pronounced diffuse fibrosis in the lungs three weeks after bleomycin administration.</p