Mutant rhodopsin transgene expression on a null background

Invest Ophthalmol Vis Sci. 2001 Mar;42(3):826-33.


Purpose: To study mechanisms leading to photoreceptor degeneration in mouse models for autosomal dominant retinitis pigmentosa (adRP) based on the rhodopsin P23H mutation.

Methods: Mice of a transgenic line expressing a rhodopsin triple mutant, V20G, P23H, and P27L (GHL), were mated with rhodopsin (rho) knockout mice. Littermates of various ages and genotypes (GHL+rho+/+, GHL+rho+/-, and GHL+rho-/-) were examined for outer nuclear layer thickness and outer segment formation (histology), fate of mutant rhodopsin (immunocytochemistry), and photoreceptor function (electroretinogram; ERG).

Results: Mice expressing GHL-rhodopsin in the absence of wild-type rhodopsin had severe retinopathy, which was nearly complete by postnatal day (P)30. GHL-rhodopsin formed homodimers nearly exclusively on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels, whereas wild-type rhodopsin predominantly formed monomers. Expression level of mutant rhodopsin in predegenerate (P10) GHL+rho-/- retinas was low, approximately 10% to 25% of normal levels. No elaboration of disc membrane or outer segment formation was observed at any time point examined. The mutant rhodopsin was found mostly in perinuclear locales (endoplasmic reticulum; ER) as evidenced by colocalization using the antibodies Rho1D4 and calnexin-NT.

Conclusions: GHL-rhodopsin dimerizes, localizes to the ER, and fails to transport and support outer segment formation. Additionally, the mutant protein does not support a scotopic ERG a-wave and accelerates photoreceptor degeneration over that occurring with the rhodopsin knockout alone. These findings indicate a cytotoxic effect of the mutant protein, probably elicited by an unfolded protein response.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • DNA Primers / chemistry
  • Electrophoresis, Polyacrylamide Gel
  • Electroretinography
  • Female
  • Fluorescent Antibody Technique, Indirect
  • Gene Expression
  • Genotype
  • Immunoblotting
  • Male
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Microscopy, Immunoelectron
  • Mutation*
  • Photoreceptor Cells, Vertebrate / metabolism
  • Photoreceptor Cells, Vertebrate / ultrastructure*
  • Retinal Degeneration / genetics*
  • Retinal Degeneration / metabolism
  • Retinal Degeneration / pathology
  • Rhodopsin / genetics*
  • Rhodopsin / metabolism
  • Transgenes / genetics*


  • DNA Primers
  • Rhodopsin