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Donita Garland, Anil Kumar Chekuri, Venkata Ramana Murthy Chavali, John Suk, Shyamanga Borooah, Radha Ayyagari; HTRA1 is increased in Bruch's membrane/choroid in a mouse model of L-ORD. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4897.
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Late onset retinal degeneration, L-ORD, is an autosomal dominant disorder with striking similarities to AMD including the formation of sub-RPE basal deposits. The S163R mutation in the C1QTNF5 gene was identified as a cause of the disorder. CTRP5, complement 1q tumor necrosis factor protein 5, is expressed and secreted by the RPE, is associated with Bruch's membrane and may have a role in the organization of extracellular matrix. The purpose of this study was to elucidate potential mechanisms underlying L-ORD by analyzing the proteins in Bruch's membrane/choroid and the associated basal deposits in a mouse model ofL-ORD.
Knock-in mice heterozygous (Ctrp5+/-) and homozygous (Ctrp5+/+) for the S163R mutation, Ctrp5 knockout mice (Ctrp5-/-) and wild type C57BL/6 mice were studied. Bruch's membrane/choroid was dissected from eyes from 5 and 18 mo mice. Samples were composites from 4 or more mice and up to 4 samples of each genotype and time point were analyzed (total of 24 samples). Proteins were solubilized, in-gel trypsin digested and the peptide masses were determined by mass spectrometry. Identification and quantification of peptides and proteins were done using MaxQuant software.
Principal component analysis showed that the major differences among all samples were primarily related to age and secondarily to genetics. The major proteins with altered expression levels that led to these separations include extracellular matrix (ECM) components, proteins with roles in maintaining the integrity of extracellular matrix and immune system related proteins. The Ctrp5 mutation led to decreased levels of some ECM proteins and to changes in the accumulation of other ECM proteins with age. The major changes observed were for CTRP5 and HTRA1. A 10 fold increase in CTRP5 was observed in 5 mo heterozygous knock-in mice (Ctrp5+/-) and a 20 fold increase was observed in 5 mo homozygous knock-in mice (Ctrp5+/+). The serine protease HTRA1 was increased fivefold in 5 mo heterzygous knock-in mice (Ctrp5+/-) and 15 fold in 5 mo homozygous knock-in mice (Ctrp5+/+). In the Ctrp5 knockout mice (Ctrp5-/-) the levels of HTRA1 were similar to that in wild type mice.
The results suggest that the pathology of L-ORD may be the result of an increase in HTRA1 and/or the accumulation of mutant CTRP5 and altered extracellular matrix composition and structure.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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