%0 Journal Article
%T Characterization of rabbit myocilin: Implications for human myocilin glycosylation and signal peptide usage
%A Allan R Shepard
%A Nasreen Jacobson
%A Ruifang Sui
%A H Thomas Steely
%A Andrew J Lotery
%A Edwin M Stone
%A Abbot F Clark
%J BMC Genetics
%D 2003
%I BioMed Central
%R 10.1186/1471-2156-4-5
%X We have cloned the rabbit ortholog of human MYOC. Rabbit MYOC consists of three exons and an open reading frame encoding a 490 amino acid, 54,882-Da protein, which is 14 amino acids shorter at the N-terminus than human myocilin but 84% identical overall. Rabbit myocilin migrates as a single electrophoretic band, vs. double-banded human myocilin, by SDS-PAGE/immunoblot analysis. We determined that the differential migration exhibited is due to an N-glycosylation site that is present in human (Asn57), monkey and mouse myocilin but absent in rabbit (Ser43), rat and bovine myocilin. Rabbit myocilin is secreted in vitro in trabecular meshwork cell culture and in vivo in aqueous humor. Secretion of human myocilin is shown to be dependent on the signal peptide and independent of the extra 14 amino acids not found in rabbit myocilin. Many of the amino acids in myocilin that are mutated in glaucoma patients are conserved across species.We have cloned the rabbit MYOC cDNA and determined that rabbit myocilin is secreted but not N-linked glycosylated. Knowledge of the rabbit MYOC cDNA sequence will facilitate future studies in the rabbit animal model examining the role of myocilin in steroid-induced glaucoma and the gain-of-function hypothesis in open-angle glaucoma.Mutations in MYOC have been shown to be causative for primary open angle glaucoma (POAG) [1-3]. Glucocorticoids have been implicated in ocular hypertension and glaucoma due to increased plasma cortisol levels [4,5] and altered cortisol metabolism [6,7] in POAG patients and from the increased risk of developing POAG in steroid-responsive patients [8,9]. Myocilin has been shown to be upregulated in glucocorticoid-treated human trabecular meshwork (TM) cells [10,11], and there is variable evidence for increased MYOC expression in glaucomatous individuals [12-14]. In addition, glaucoma patients have a higher chance of responding to steroids than non-glaucomatous individuals. However, an extensive study of mutations in t
%U http://www.biomedcentral.com/1471-2156/4/5