Cell-Type-Specific Complement Profiling in the ABCA4^-/- Mouse Model of Stargardt Disease

Area of Science:

• Ophthalmology
• Immunology
• Genetics

Background:

• Stargardt macular degeneration is an inherited retinal disease.
• Mutations in the ATP-binding cassette subfamily A member 4 (ABCA4) gene cause this condition.
• The role of the complement system in ABCA4-related retinal degeneration is not fully understood.

Purpose of the Study:

• To characterize the complement expression profile in ABCA4 knockout mouse retinas.
• To correlate complement findings with morphological markers of retinal degeneration.
• To investigate the impact of ABCA4 deficiency on complement homeostasis in the retina.

Main Methods:

• Analysis of complement gene and protein expression in ABCA4-/- mice.
• Morphological assessment of retinal degeneration.
• Measurement of complement C3b/C3 and C3d/C3 ratios in retinal tissues and serum.
• Evaluation of complement factor I (CFI) levels.

Main Results:

• ABCA4-/- mice exhibited enhanced retinal pigment epithelium (RPE) autofluorescence and inner retinal cell loss.
• Increased C3 expression and decreased CFI transcripts were observed in specific retinal cells of ABCA4-/- mice.
• Protein analysis confirmed reduced CFI and elevated C3b/C3 ratios in the retina and RPE/choroid of ABCA4-/- mice.
• Increased C3d/C3 ratio in serum of ABCA4-/- mice, with no change in CFI.

Conclusions:

• The findings suggest an overactive complement cascade in ABCA4-/- retinas.
• Complement dysregulation may contribute to pathological alterations like microglial activation and neurodegeneration.
• Maintaining complement homeostasis is crucial for retinal integrity.