Abstract
Purpose: :
The RPE65-/- mouse is a model system to study Leber congenital amaurosis (LCA), a severe form of retinal dystrophy [OMIM 204000]. To evaluate the role of the interphotoreceptor matrix (IPM) during this retinal degeneration, we analyzed the expression of interphotoreceptor matrix proteoglycan 1 (IMPG1), IMPG2, CD44 and neuroglycan C (NGC).
Methods: :
IMPG1, IMPG2, CD44 and NGC mRNA expression was assessed by oligonucleotide microarray, quantitative PCR and in situ hybridization in retinas of 2-, 4-, 6- and 12-month old C57/Bl6 wild-type and RPE65-/- mice. Retinal NGC protein expression was analyzed by Western Blot and immunohistochemistry.
Results: :
The mRNA expression of IMPG2, CD44 and NGC was upregulated by 2- to 4-fold at all time-points in RPE65-/- retinas. IMPG2, CD44 and NGC mRNAs were highly expressed in the ganglion cell layer, the inner nuclear layer and at the outer limiting membrane. NGC mRNA was furthermore detected in the retinal pigment epithelium (RPE), where its expression was not upregulated during retinal degeneration. NGC-I exhibited a tissue-specific mRNA expression with highest levels in the RPE, NGC-II was expressed in all ocular tissues and NGC-III was barely detected. NGC protein was markedly upregulated in RPE65-/- retinas. In this model, NGC was also expressed at highest levels on the apical membrane of RPEs.
Conclusions: :
It is tempting to speculate that the upregulation of IPM components during retinal degeneration in RPE65-/- mice is a potential mechanism to maintain the integrity of photoreceptor outer segments.
Keywords: degenerations/dystrophies • extracellular matrix • proteoglycans/glycosaminoglycans