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Olfactomedin 1 (OLFM1) is a secreted glycoprotein and member of the olfactomedin protein family, which is preferentially expressed in various areas throughout the central nervous system. To learn about the functional properties of OLFM1 in the eye, we investigated its localization in the mouse and pig eye. In addition, we analyzed the ocular phenotype of Olfm1 mutant mice in which 52 amino acids were deleted in the central part (M2 region) of OLFM1. OLFM1 was detected in cornea, sclera, retina, and optic nerve of both wild-type and Olfm1 mutant littermates. By immunohistochemistry and double labeling with the lectin peanut agglutinin, OLFM1 was found in the interphotoreceptor matrix (IPM) of mouse and pig retina where it was directly localized to the inner segments of photoreceptors. Western blotting confirmed the presence of the OLFM1 isoforms pancortin 1 (BMY) and pancortin 2 (BMZ) in the IPM. The retinal phenotype of Olfm1 mutant mice did not obviously differ from that of wild-type littermates. In addition, outer nuclear layer (ONL) and total retinal thickness were not different, and the same was true for the area of the optic nerve in cross sections. Functional changes were observed though by electroretinography, which showed significantly lower a- and b-wave amplitudes in Olfm1 mutant mice when compared to age-matched wild-type mice. When light damage experiments were performed as an experimental paradigm of photoreceptor apoptosis, significantly more TUNEL-positive cells were observed in Olfm1 mutant mice 30 h after light exposure. One week after light exposure, the ONL was significantly thinner in Olfm1 mutant mice than in wild-type littermates indicating increased photoreceptor loss. No differences were observed when rhodopsin turnover or ERK1/2 signaling was investigated. We conclude that OLFM1 is a newly identified IPM molecule that serves an important role for photoreceptor homeostasis, which is significantly compromised in the eyes of Olfm1 mutant mice.

Myocilin is a 55-57kDa secreted glycoprotein and member of the olfactomedin family, which is mutated in some forms of primary open-angle glaucoma. To assess the effects of elevated amounts of myocilin on aqueous humor outflow dynamics in an in vivo system, transgenic betaB1-crystallin-MYOC mice have been developed that strongly overexpress myocilin in their eyes. The transgenic overexpression of myocilin results in an almost five-fold increase of secreted normal myocilin in the aqueous humor of betaB1-crystallin-MYOC mice. In the present study, we wanted to use betaB1-crystallin-MYOC as a tool to identify the response of ocular tissues to the presence of higher than normal amounts of myocilin, and to identify changes in gene expression that could help to shed light on the functional in vivo properties of myocilin. RNA was isolated from ocular tissues of betaB1-crystallin-MYOC mice and wild-type littermates. Changes in gene expression were determined by hybridization of gene microarrays and confirmed by real time RT-PCR and Western blotting. The expression of genes that had been found to be differentially regulated in betaB1-crystallin-MYOC mice was further analyzed in cultured human trabecular meshwork (HTM) cells treated with recombinant myocilin. Although betaB1-crystallin-MYOC mice do not have an obvious phenotype, a statistically significant up- and downregulation of several distinct genes was found when compared to gene expression in wild-type littermates. Among the genes that were found to be differentially regulated were Wasl, Ceacam1, and Spon2, which are involved in cell adhesion and cell-matrix interactions. Differences in expression were also found for Six1 which encodes for a transcription factor, and for Pftk1 whose gene product is a cdc2-related protein kinase. The expression of these genes was also found to be regulated in vitro in HTM cells treated with recombinant myocilin. Substantially higher amounts in ocular tissues of betaB1-crystallin-MYOC mice were found for connexin 46 and alphaB-crystallin. In addition, several genes that encode for olfactomedin proteins showed distinct changes in expression. Olfml3 was significantly downregulated, while Lphn1, Lphn2, and Lphn3 were significantly upregulated. Our findings support a role for myocilin in modulating cellular adhesion, and suggest functional processes that involve other proteins of the olfactomedin family.

International audience; Purpose: To describe retinal alterations detected by swept-source optical coherence tomography (SS-OCT) in paediatric patients with Usher syndrome type 1 (USH1) and to compare these findings to previously published reports.Methods: Thirty-two eyes from 16 patients (11 males and 5 females) with a genetic diagnosis of USH1 because of MYO7A mutations underwent SS-OCT. Patients ranged in age from 4 to 17 years (mean, 11,13 ± 4,29). The subfoveal and macular area were analysed with SS-OCT at 1050 nm using 12 radial scans of 12.0 mm. Structural abnormalities were evaluated and correlated with best-corrected visual acuity (BCVA).Results: The most common qualitative retinal abnormality was external layer damage in macular area. Specific alterations included external limiting membrane loss/disruption (27 eyes; 84.4%), disruption of the Myoid zone (27 eyes; 84.4%); Ellipsoid zone disruption (28 eyes; 87.5%), and loss of the outer segments (29 eyes; 90.6%). The damage of the retinal pigment epithelium was divided according to the loss of the different layers: phagosome zone (30 eyes; 93.8%), melanosome zone (29 eyes; 90.6%) and mitochondria zone (0 eyes; 0%). The presence of cystoid macular oedema (CMO) was significantly correlated with alterations in photoreceptors. Disruption or absence of the myoid and ellipsoid zones of the photoreceptors were the only variables independently associated with decreased BCVA.Conclusions: The findings of this study suggest that the physiopathologic basis of early-stage Usher syndrome (USH) may be changes in the outer retinal layer, particularly the photoreceptors, which in turn may cause alterations-such as CMO-in the inner retinal layers. Accordingly, monitoring the condition of photoreceptors during follow-up may be advisable for the early detection of pathologic changes.