Abstract
Purpose :
Late onset retinal degeneration, L-ORD, is an autosomal dominant macular degeneration with marked similarities to AMD including the formation of sub-RPE basal deposits. We have identified 3 different mutations in the C1q tumor necrosis factor-related protein 5 (C1QTNF5/CTRP5) gene as the underlying cause of L-ORD. In knock-in mouse models of L-ORD which carry the S163R Ctrp5 mutation (KI/WT and KI/KI) large increases in mutant CTRP5 and the serine protease HTRA1 were present in Bruch’s membrane/choroid. Both proteins have roles in the homeostasis of extracellular matrix. Subsequent studies showed the pathology of L-ORD due to the S163R Ctrp5 mutation is likely mediated through HTRA1 (Chekuri et al Aging Cell 2019). The purpose of this study was to further elucidate potential mechanisms underlying L-ORD pathology by an in-depth analysis of the proteomes of BrM-Ch in the mouse models of L-ORD.
Methods :
Bruch’s membrane/choroid was dissected from S163R Ctrp5 (KI/WT and KI/KI) mutant and wild type mice at 5 and 18 mo. Proteomes of BrM-Ch were determined using proteomic strategies and mass spectrometry. Identification and label-free quantification of peptides and proteins were done using MaxQuant software. Significant changes in protein levels were determined using multiple statistical analyses.
Results :
The major differences in protein levels among all samples were related primarily to age and secondarily to genetics. The major proteins with altered levels correlating with both age and genetics included ECM components, proteins with roles in maintaining the integrity of ECM and immune system related proteins. Increased levels of four mast cell proteases, tryptase (Tpsb2), carboxypeptidase A (Cpa3), chymase (Cma1) and mast cell protease 4 (Mcpt4), also correlated with both aging and genetics in S163R Ctrp5 (KI/WT and KI/KI) mutant and wild type mice. In KI/WT mice each enzyme increased over 10 fold from 5 mo to 18 mo. The levels for the 4 enzymes were comparable in mutant and wild type mice at 5 mo. Mast cell proteases have reported roles in processing/degrading ECM components. These results provide a possible link between the immune system and altered ECM structure and function in L-ORD.
Conclusions :
These results further implicate the immune system and altered extracellular matrix composition and structure in the pathology of L-ORD.
This is a 2020 ARVO Annual Meeting abstract.