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A.H. Conrad, G.W. Conrad; Keratocan Gene Expression in Developing Chick Ocular and Non-Ocular Tissues . Invest. Ophthalmol. Vis. Sci. 2003;44(13):864.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Keratan sulfate proteoglycan [KSPG] core protein keratocan mRNA is expressed predominantly in adult vertebrate cornea. We asked [a] which cells in developing chick cornea express keratocan mRNA, and when, relative to sulfated KS appearance, and [b] what non-ocular tissues express keratocan mRNA during embryogenesis, and do they also make sulfated KS? Methods: Keratocan probe was generated from an 833bp Kera cDNA, lumican probe from a 944bp Lum cDNA [Dunlevy et al., J. Biol. Chem. 273:9615-9621, 1998], and noelin probe from a 629bp cDNA obtained by RT-PCR from HH7 embryo RNA [Barenbaum et al., Nature Cell Biol. 2:219-225, 2000]. WISH was performed as described by Henrique et al. [Nature 375:787-790, 1995], section in situ hybridization as described by Etchevers et al. [Development 128:1059-1168, 2001], and staining with I22 antibody against sulfated KS as described by Funderburgh et al. [Dev. Biol. 116:267-277, 1986]. Results: Keratocan mRNA is expressed by neural crest [NC]-derived head mesenchyme surrounding the anterior eye on embryonic day 3.5 [E3.5], by all corneal endothelial cells from E 4.5, when they first migrate across the primary stroma, onward, by all keratocytes from E6, as soon as they migrate into corneal stroma, onward, and by distal surface iris cells from E8, when iris first forms, onward, but never by corneal epithelial cells. Expression in the limbus ends by E8. In contrast, lumican mRNA is expressed throughout iris and limbus. Corneal stroma I22 staining begins on E9, but is never seen in head mesenchyme, iris, or limbus. Keratocan mRNA expression along the embryo A-P and D-V axes begins as early as HH7 in mesenchyme flanking midbrain neural folds [but not in noelin mRNA + premigratory NC cells], then spreads posteriorly in trunk dorsal mesenchyme, and ventrally in cranial mesenchyme through HH20. During E3.5 and E4.5 it concentrates in anterior periocular, pericranial nerve, and subepithelial pharyngeal arch head mesenchymes, dorsolateral subepithelium, sclerotome, perisclerotome and pronephrogenic trunk mesenchymes, and dorso-proximal and discrete distal limb mesenchymes, but is not expressed in noelin mRNA + NC-derived dorsal root ganglia [DRGs] or DRG outgrowths. I22 does not stain embryos younger than HH20, and stains E3.5 and E4.5 embryos only in notochord. Conclusions: Developmentally regulated keratocan mRNA is expressed in some regions of ocular and non-ocular NC-derived and non-NC-derived mesenchymes, but not in premigratory NC or NC-derived nerves. Sulfated KS is not detected in these keratocan mRNA expressing embryonic mesenchymes.
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