Biomedical subjects

John G Flannery

Publications and source records attributed to John G Flannery.

4 recordsLinked to original sources

PubMed2006

Looking within for vision.

Channelrhodopsin-2 (ChR2), a directly light-gated cation channel from the green alga Chlamydomonas reinhardtii has been shown to be a directly light-switched cation-selective ion channel, which employs 11-cis retinal as its chromophore. This is the same chromophore as the mammalian photoreceptor's visual pigment-rhodopsin. Previously, investigators demonstrated that ChR2 can be used to optically control neuronal firing by depolarizing the cell. In this issue of Neuron, Bi et al. apply viral-mediated gene transfer to deliver ChR2 to retinal ganglion cells (RGC) in a rodent model of inherited blindness. In this way, the authors have genetically engineered surviving retinal neurons to take on the lost photoreceptive function. The conversion of light-insensitive retinal interneurons into photosensitive cells introduces an entirely new direction for treatments of blinding retinal degeneration.

Animals↗

PubMed2006

Characterization of peripherin/rds and rom-1 transport in rod photoreceptors of transgenic and knockout animals.

PURPOSE: Peripherin/rds and rom-1 have structural roles in morphogenesis and stabilization of the outer segment, but little is known about their transport and sorting to the rod outer segment. Peripherin/rds and rom-1 trafficking were studied in several knockout and transgenic animal models. METHODS: Rod outer segment formation and distribution of peripherin/rds and rom-1 were examined by immunohistochemistry, electron microscopy, and molecular biological methods in wild-type, rhodopsin-knockout, and peripherin/rds-knockout mice. C-terminally truncated peripherin/rds (Xper38)-GFP chimeric protein sorting was followed by immunofluorescence microscopy in transgenic Xenopus. RESULTS: In developing wild-type photoreceptors, peripherin/rds was detected exclusively in the distal tip of the connecting cilium in advance of outer segment formation. Rhodopsin-knockout mice failed to create normal rod outer segments and instead, elaborated membranous protrusions at the distal cilium tip. Peripherin/rds and rom-1 localized to this ciliary membrane in rhodopsinless photoreceptors. In transgenic Xenopus, a C-terminally truncated peripherin/rds-GFP fusion predominantly localized to its normal location within disc rims. In developing rds mice, rom-1 accumulated primarily in distal ciliary membranes. CONCLUSIONS: Peripherin/rds transport and localization are polarized to the site of outer segment morphogenesis before disc formation in developing photoreceptors. Peripherin/rds and rom-1 trafficking is maintained in rhodopsin-knockouts, suggesting that rim proteins and rhodopsin have separate transport pathways. The presence of truncated peripherin/rds-GFP in the outer segment supports previous evidence that peripherin/rds mice form homotetramers for outer segment targeting. The finding that rom-1 transports to the outer segment domain in rds mice suggests that rom-1 may possess its own sorting and transport signals.

Animals↗

PubMed2004

Range of retinal diseases potentially treatable by AAV-vectored gene therapy.

Viable strategies for retinal gene therapy must be designed to cope with the genetic nature of the disease and/or the primary pathologic process responsible for retinal malfunction. For dominant gene defects the aim must be to destroy the presumably toxic gene product, for recessive gene defects the direct approach aims to provide a wild-type copy of the gene to the affected retinal cell type, and for diseases of either complex or unknown genetic origin, more general cell survival strategies that deal with preserving affected retinal cells are often the best and only option. Hence examples of each type of therapy will be briefly discussed in several animal models, including ribozyme therapy for autosomal dominant retinitis pigmentosa in the transgenic P23H opsin rat, beta-PDE gene augmentation therapy for autosomal recessive retinitis pigmentosa in the rd mouse, glial cell-derived neurotrophic factor (GDNF) gene therapy for autosomal dominant RP in the transgenic S334ter opsin rat and pigment epithelial cell-derived neurotrophic factor (PEDF) gene therapy for neovascular retinal disease in rodents. Each employs a recombinant AAV vectored passenger gene controlled by one of several promoters supporting either photoreceptor-specific expression or more general retinal cell expression depending on the therapeutic requirements.

Animals↗

PubMed2002

USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses.

Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterised by the association of post-lingual progressive hearing loss, progressive visual loss due to retinitis pigmentosa and variable presence of vestibular dysfunction. Because the previously defined transcripts do not account for all USH3 cases, we performed further analysis and revealed the presence of additional exons embedded in longer human and mouse USH3A transcripts and three novel USH3A mutations. Expression of Ush3a transcripts was localised by whole mount in situ hybridisation to cochlear hair cells and spiral ganglion cells. The full length USH3A transcript encodes clarin-1, a four-transmembrane-domain protein, which defines a novel vertebrate-specific family of three paralogues. Limited sequence homology to stargazin, a cerebellar synapse four-transmembrane-domain protein, suggests a role for clarin-1 in hair cell and photoreceptor cell synapses, as well as a common pathophysiological pathway for different Usher syndromes.

Amino Acid Sequence↗