Transgenic expression of constitutively active RAC1 disrupts mouse rod morphogenesis

Research output: Contribution to journalArticle

Abstract

PURPOSE: Dominant-active RAC1 rescues photoreceptor structure in Drosophila rhodopsin-null mutants, indicating an important role in morphogenesis. This report assesses the morphogenetic effect of activated RAC1 during mammalian rod photoreceptor development using transgenic mice that express constitutively active (CA) RAC1.

METHODS: Transgenic mice were generated by expressing CA RAC1 under control of the Rhodopsin promoter, and morphological features of the photoreceptors were evaluated by histology, immunohistochemistry, and transmission electron microscopy. Function was evaluated by electroretinography. Potential protein partners of CA RAC1 were identified by co-immunoprecipitation of retinal extracts.

RESULTS: Constitutively active RAC1 expression in differentiating rods disrupted outer retinal lamination as early as postnatal day (P)6, and many photoreceptor cell nuclei were displaced apically into the presumptive subretinal space. These photoreceptors did not develop normal inner and outer segments and had abnormal placement of synaptic elements. Some photoreceptor nuclei were also mislocalized into the inner nuclear layer. Extensive photoreceptor degeneration was subsequently observed in the adult animal. Constitutively active RAC1 formed a complex with the polarity protein PAR6 and with microtubule motor dynein in mouse retina. The normal localization of the PAR6 complex was disrupted in CA RAC1-expressing rod photoreceptors.

CONCLUSIONS: Constitutively active RAC1 had a profound negative effect on mouse rod cell viability and development. Rod photoreceptors in the CA RAC1 retina exhibited a defect in polarity and migration. Constitutively active RAC1 disrupted rod morphogenesis and gave a phenotype resembling that found in the Crumbs mutant. PAR6 and dynein are two potential downstream effectors that may be involved in CA RAC1-mediated defective mouse photoreceptor morphogenesis.

Details

Authors
  • Hongman Song
  • Ronald A Bush
  • Camasamudram Vijayasarathy
  • Robert N Fariss
  • Sten Kjellstrom
  • Paul A. Sieving
External organisations
  • National Institutes of Health, United States
Research areas and keywords

Keywords

  • Animals, Blotting, Western, DNA, Electroretinography, Gene Expression Regulation, Developmental, Immunohistochemistry, Mice, Mice, Transgenic, Microscopy, Electron, Transmission, Morphogenesis, Neuropeptides, Phenotype, Retinal Degeneration, Retinal Rod Photoreceptor Cells, rac1 GTP-Binding Protein, Journal Article, Research Support, N.I.H., Intramural
Original languageEnglish
Pages (from-to)2659-68
JournalInvestigative Ophthalmology and Visual Science
Volume55
Issue number4
Publication statusPublished - 2014 Apr 25
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes