Proteoglycans contain a 4.6-A repeat in corneas with macular dystrophy: II. Histochemical evidence.
OBJECTIVE
Synchrotron x-ray diffraction experiments indicate that corneas with macular corneal dystrophy (MCD) contain unusual 4.6-A periodic repeats thought to reside in proteoglycans or glycosaminoglycans. Recently the 4.6-A x-ray reflection was found to be significantly diminished after incubation of MCD specimens in buffer containing chondroitinase ABC or N-glycanase. We examined the sulfated proteoglycans in these glycosidase-digested MCD corneas.


METHODS
Transmission electron microscopy was used in conjunction with cuprolinic blue-staining for sulfated proteoglycans.


RESULTS
Incubation of an MCD specimen in enzyme buffer left both small and large proteoglycan filaments in the stromal matrix, whereas incubation in the presence of chondroitinase ABC removed these molecules from the tissue. Incubation in buffer containing N-glycanase, on the other hand, removed the large proteoglycan filaments from the MCD stroma but left unaffected the small collagen-associated proteoglycans.


CONCLUSIONS
These results are consistent with the interpretation that 4.6-A periodic repeats in MCD corneas reside in large sulfated proteoglycan filaments (or aggregates thereof) that may contain chondroitin/dermatan sulfate and keratan sulfate or keratan components.
Quantock
A J
AJ
Anheuser-Busch Eye Institute, Department of Ophthalmology, St. Louis University School of Medicine, Missouri, USA.
Klintworth
G K
GK
Schanzlin
D J
DJ
Lenz
M E
ME
Thonar
E J
EJ
D002807:Chondroitin / Q000032:analysis / Q000648:ultrastructure; D002808:Chondroitin Lyases / Q000494:pharmacology; D004396:Coloring Agents; D003317:Corneal Dystrophies, Hereditary / Q000378:metabolism / Q000473:pathology*; D003319:Corneal Stroma / Q000737:chemistry / Q000648:ultrastructure*; D003470:Culture Media; D003871:Dermatan Sulfate / Q000032:analysis / Q000648:ultrastructure; D004797:Enzyme-Linked Immunosorbent Assay; D006651:Histocytochemistry; D006801:Humans; D007211:Indoles; D007632:Keratan Sulfate / Q000032:analysis / Q000648:ultrastructure; D008854:Microscopy, Electron; D009942:Organometallic Compounds; D011509:Proteoglycans / Q000032:analysis / Q000648:ultrastructure*; D014961:X-Ray Diffraction
D004396:Coloring Agents; D003470:Culture Media; D007211:Indoles; D009942:Organometallic Compounds; D011509:Proteoglycans; D003871:Dermatan Sulfate; C015445:copper phthalocyanine; D002807:Chondroitin; D007632:Keratan Sulfate; D002808:Chondroitin Lyases