Atypical composition and ultrastructure of proteoglycans in the mouse corneal stroma.
OBJECTIVE
Recently, gene-targeted strains of mice with null mutations for specific proteoglycans (PGs) have been used for investigations of the functional role of these molecules. In the present study, the corneal stroma of the mouse was examined to provide some baseline PG morphologies in this species.


METHODS
Monoclonal antibodies to specific glycosaminoglycan (GAG) chain sulfation patterns were used to characterize PG composition in corneal extracts by SDS-PAGE and Western blot analysis and to identify their tissue distribution by immunofluorescence microscopy. PGs were also visualized by transmission electron microscopy after contrast enhancement with cationic dye fixation.


RESULTS
Western blot analysis of pooled corneal extracts and immunofluorescence of tissue sections identified 4-sulfated, but not 6-sulfated, chondroitin sulfate/dermatan sulfate (CS/DS). Keratan sulfate (KS) was present only as a low-sulfated moiety. Electron microscopic histochemistry disclosed a complex array of corneal PGs present as (1) fine filaments radiating from collagen fibrils, and (2) elongate, straplike structures, running either along the fibril axis or weaving across the primary fibril orientation. These large structures were digested by chondroitinase ABC, but not by keratanase.


CONCLUSIONS
KS in the mouse is predominantly undersulfated and generates an immunostaining pattern that differs from that observed in corneas of other mammalian species thus far investigated. The mouse cornea resembles other mammalian corneas in the presence of filamentous arrays of small, collagen-associated stromal PGs visualized by cationic dye staining. However, large dye-positive structures with a CS/DS component are also present and appear to be unique to the cornea of this species.
Young
Robert D
RD
School of Optometry and Vision Sciences, Cardiff University. UK.
Tudor
Debbie
D
Hayes
Anthony J
AJ
Kerr
Briedgeen
B
Hayashida
Yasutaka
Y
Nishida
Kohji
K
Meek
Keith M
KM
Caterson
Bruce
B
Quantock
Andrew J
AJ
D000818:Animals; D015153:Blotting, Western; D002809:Chondroitin Sulfates / Q000032:analysis / Q000648:ultrastructure; D004396:Coloring Agents / Q000378:metabolism; D003319:Corneal Stroma / Q000737:chemistry* / Q000648:ultrastructure*; D003871:Dermatan Sulfate / Q000032:analysis / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D007211:Indoles / Q000378:metabolism; D007632:Keratan Sulfate / Q000032:analysis / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009942:Organometallic Compounds / Q000378:metabolism; D011509:Proteoglycans / Q000032:analysis* / Q000648:ultrastructure*; D013194:Staining and Labeling / Q000379:methods
D004396:Coloring Agents; D007211:Indoles; D009942:Organometallic Compounds; D011509:Proteoglycans; D003871:Dermatan Sulfate; C015445:copper phthalocyanine; D002809:Chondroitin Sulfates; D007632:Keratan Sulfate