Mutant Fibulin-3 Causes Proteoglycan Accumulation and Impaired Diffusion Across Bruch's Membrane

Invest Ophthalmol Vis Sci. 2017 Jun 1;58(7):3046-3054. doi: 10.1167/iovs.17-21720.


Purpose: The mutation R345W in EFEMP1 (fibulin-3) causes macular degeneration. This study sought to determine whether proteoglycan content and diffusion across Bruch's membrane are altered in Efemp1ki/ki mice carrying this mutation or in Efemp1-/- mice.

Methods: Proteoglycans in mouse Bruch's membranes were stained with Cupromeronic Blue (CB). Heparan sulfated proteoglycan (HSPG) and chondroitin/dermatan sulfate proteoglycan (C/DSPG) distributions were visualized following treatments with chondroitinase ABC (C-ABC) or nitrous acid. Total sulfated glycosaminoglycans (sGAGs) in Bruch's membrane/choroid (BrM/Ch) were measured with dimethylmethylene blue (DMMB). Matrix metalloprotease (MMP)-2, MMP-9, and tissue inhibitor of metalloproteinase (TIMP)-3 were examined by immunofluorescence and quantified using Image J. Molecules with different Stokes radius (Rs) were allowed simultaneously to diffuse through mouse BrM/Ch mounted in a modified Ussing chamber. Samples were quantified using gel exclusion chromatography.

Results: HSPGs and C/DSPGs were markedly increased in Efemp1ki/ki Bruch's membrane, and MMP-2 and MMP-9 were decreased, but TIMP-3 was increased. Diffusion across Efemp1ki/ki Bruch's membrane was impaired. In contrast, the proteoglycan amount in Efemp1-/- Bruch's membrane was not significantly different, but the size of proteoglycans was much larger. MMP-2, MMP-3, and TIMP-3 levels were similar to that of Efemp1+/+ mice, but they were localized diffusely in retinal pigment epithelium (RPE) cells instead of Bruch's membrane. Diffusion across Efemp1-/- Bruch's membrane was enhanced.

Conclusions: Mutant fibulin-3 causes proteoglycan accumulation, reduction of MMP-2 and MMP-9, but increase of TIMP-3, and impairs diffusion across Bruch's membrane. Fibulin-3 ablation results in altered sizes of proteoglycans, altered distributions of MMP-2, MMP-9, and TIMP-3, and enhances diffusion across Bruch's membrane.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / genetics
  • Animals
  • Bruch Membrane / metabolism*
  • Bruch Membrane / pathology
  • DNA / genetics*
  • DNA Mutational Analysis
  • Disease Models, Animal
  • Extracellular Matrix Proteins / genetics*
  • Extracellular Matrix Proteins / metabolism
  • Macular Degeneration / diagnosis
  • Macular Degeneration / genetics*
  • Macular Degeneration / metabolism
  • Mice
  • Mice, Mutant Strains
  • Mutation*
  • Proteoglycans / metabolism*


  • Efemp1 protein, mouse
  • Extracellular Matrix Proteins
  • Proteoglycans
  • DNA