Arl3 Rod-Specific Knockout Displays RP-Like Photoreceptor Degeneration

Untitled-1

This abstract was presented today at the 2014 Association for Research in Vision and Opthalmology (ARVO) meetings in Orlando, Florida by Christin Hanke, Houbin Zhang, Cecilia D. Gerstner, Jeanne M. Frederick AND Wolfgang Baehr.

Full size poster can be downloaded here.

Purpose: Arf-like protein 3 (Arl3) localizes predominantly in the photoreceptor inner segment. Germline Arl3 knockout mice do not survive beyond PN 21 and display multiple organ ciliary defects as well as retinal regeneration (Schrick et al., (2006). Am. J. Pathol. 168, 1288-1298). We therefore generated rod-specific Arl3 knockouts to elucidate the role of Arl3 in transport of photoreceptor membrane-associated proteins.

Methods: Knockouts containing a gene trap in intron 1 of the Arl3 gene were generated using a EUCOMM cell line. Breeding with Flp mice, followed by mating with iCre75+ mice, generated rod-specific knockouts. Photoreceptor function and retina morphology of wild-type (WT) and mutant mice were analyzed by confocal microscopy, ERG and immunohistochemistry. An Arl3-specific polyclonal antibody (Ab) was generated using a full-length recombinant Arl3 polypeptide expressed in bacteria.

Results: Western blot of WT retina with anti-Arl3-Ab identified a 20 kDa protein, which was significantly reduced in two month-old mutant (Arl3flox/flox;iCre75+) retina. Immunohistochemistry revealed Arl3 localization predominantly in the inner segments of WT photoreceptor cells. Arl3 immunoreactivity was absent in homozygous rod knockouts, but still present in cones and the inner retina. Scotopic and photopic ERGs of rod knockout and WT mice at PN15 had comparable amplitudes suggesting normal phototransduction. Retina histology of PN15 knockout mice was comparable to WT. One month-old Arl3flox/flox;iCre75+ mice showed reduced (80-90%) scotopic, but normal photopic ERG responses. In retinas of two month-old knockout mice, scotopic ERGs were extinguished, whereas cone ERGs were highly attenuated. Retinas of one month-old homozygous knockout mice had 4-5 rows of nuclei in the ONL, and only one row in two month-old mice. Immunohistochemistry of PN 15 and one month-old retina sections revealed that rhodopsin transport, as shown by rho1D4 labeling of ROS, is normal. Rhodopsin was undetectable in two month-old conditional knockout mice due to complete photoreceptor degeneration.

Conclusions: Rod-specific knockout of Arl3 revealed rapidly progressing photoreceptor degeneration, with knockout mice being completely blind at two months of age. Outer segment development appeared to be unimpaired by Arl3 deletion and rod photoreceptor function was normal at P14.

Notable paper: Lhx2 Balances Progenitor Maintenance With Neurogenic Output And Promotes Competence State Progression In The Developing Retina

Levine Cover J Neurosci

The Levine lab here at the Moran Eye Center has a new publication out in the Journal of Neuroscience and even scored the cover.  Specifically, the manuscript was authored by Patrick J. Gordon, Sanghee Yun, Anna M. Clark, Edwin S. Monuki, L. Charles Murtaugh, and Edward M. Levine.  The Levine team explored how multipotent retinal progenitor cells  (RPCs) control the ordered production of the major cell types in the mouse retina.  The key finding in this manuscript is that the Lim/Homeodomain protein, Lhx2, is a progenitor-intrinsic regulator of maintenance/self-renewal, precursor production, and competence progression. They arrived at this conclusion by generating Lhx2 conditional knockout mice at multiple stages of development using an inducible Cre-driver (Hes1CreERT2) that specifically targets progenitor cells. This approach allowed them to perform day-by-day inactivations, achieving a temporal scale of gene expression control not previously reported in the retina. This is an important advance because the properties of RPCs are constantly changing, and we are now able to directly test the regulation of these properties in an appropriate temporal manner. As such, The Levine team has identified Lhx2 as an RPC-intrinsic factor that regulates maintenance, precursor fate, and competence simultaneously.

Whole Exome Sequencing (WES) Identifies a Mutation in ALPK1 Responsible for a Novel, Autosomal Dominant Disorder of Vision Loss, Splenomegaly, and Pancytopenia

Williams 2013 ARVO final

This abstract was presented today at the Association for Research in Vision and Opthalmology (ARVO) meetings in Seattle, Washington by Lloyd B. Williams, Chad D. Huff, Denise Morgan, Rosann Robinson, Margaux Morrison, Krista Kinard, George Rodgers, Kathleen B. Digre, Kathleen and Margaret DeAngelis. Continue reading “Whole Exome Sequencing (WES) Identifies a Mutation in ALPK1 Responsible for a Novel, Autosomal Dominant Disorder of Vision Loss, Splenomegaly, and Pancytopenia”

Constructive Retinal Plasticity After Selective Ablation of the Photoreceptors

Photocoagulation_

This abstract was presented today at the Association for Research in Vision and Opthalmology (ARVO) meetings in Seattle, Washington by Corinne N. Beier, Bryan W. Jones, Philip Huie, Yannis M. Paulus, Daniel Lavinsky, Loh-Shan B. Leung, Hiroyuki Nomoto,  Robert E. MarcDaniel V. Palanker, and Alexander Sher. Continue reading “Constructive Retinal Plasticity After Selective Ablation of the Photoreceptors”

Light Transmittance of Explanted Hydrophobic Acrylic Intraocular Lenses with Surface Light Scattering

No Slide Title

This abstract was presented today at the Association for Research in Vision and Opthalmology (ARVO) meetings in Seattle, Washington by Liliana Werner, Caleb Morris, Shannon Stallings, Erica Liu, Anne Floyd, Andrew Ollerton, Lisa Leishman, Zachary Bodnar, Marcia Ong and Ali Akinay. Continue reading “Light Transmittance of Explanted Hydrophobic Acrylic Intraocular Lenses with Surface Light Scattering”

Candidate Gene Study of Retinopathy of Prematurity in Extremely Low Birthweight Infants from the Neonatal Research Network

PowerPoint Presentation

This abstract was presented today at the Association for Research in Vision and Opthalmology (ARVO) meetings in Seattle, Washington by ME Hartnett, M Morrison, G Page, M Cotten, J Murray, M DeAngelis. Continue reading “Candidate Gene Study of Retinopathy of Prematurity in Extremely Low Birthweight Infants from the Neonatal Research Network”

Knockdown of Müller Cell Specific VEGF Reduces Retinal Neovascularization In A Rat Model of Retinopathy of Prematurity

Slide 1

This abstract was presented today at the Association for Research in Vision and Opthalmology (ARVO) meetings in Seattle, Washington by Yanchao Jiang, Manabu McCloskey, Haibo Wang, Zhihong Yang, Jeremy Strange, Tal Kafir, John G Flannery, Kenneth Greenberg, Scott Hammond and ME Hartnett. Continue reading “Knockdown of Müller Cell Specific VEGF Reduces Retinal Neovascularization In A Rat Model of Retinopathy of Prematurity”