Altered collagen fibril formation in the sclera of lumican-deficient mice.
OBJECTIVE
To better understand the role of lumican (corneal keratan sulfate proteoglycan) in the scleral extracellular matrix, collagen fibril size, shape, and organization were evaluated in the sclera of wild-type mice and in mice homozygous or heterozygous for a null mutation in the lumican gene. METHODS. Anterior and posterior sclera from 6-month-old wild-type (lum+/lum+) and lumican-deficient mice (lum+/lum- and lum-/lum-) were analyzed by transmission electron microscopy. In addition, lumican was characterized in the sclera of wild-type and lumican-deficient mice by Western blot analyses.


RESULTS
Lumican was present in the mouse sclera as an approximately 48-kDa core protein containing short glycosaminoglycan side chains consisting of moderate- to low-sulfated keratan sulfate. The wild-type mouse sclera consisted of irregularly arranged lamellae of collagen fibrils with an average diameter of 47.37 +/- 0.648 nm in the anterior sclera and 54.68 +/- 0.342 nm the posterior sclera. Collagen fibrils in the sclera of lumican mutant mice (lum+/lum- and lum-/lum-) were significantly larger in diameter in anterior (72.61 +/- 0.445 and 84.47 +/- 0.394 nm, respectively) and posterior (75.92 +/- 0.361 and 80.90 +/- 0.490 nm, respectively) scleral regions compared with wild-type mice (P < 0.001).


CONCLUSIONS
The results of the present study indicate that null mutations in one or both alleles of the lumican gene result in significant defects in scleral collagen fibril formation that could lead to alterations in ocular shape and size and severely affect vision.
Austin
Bobbie A
BA
Department of Anatomy & Cell Biology, School of Medicine & Health Sciences University of North Dakota, Grand Forks, North Dakota 58202-9037, USA.
Coulon
Christopher
C
Liu
Chia-Yang
CY
Kao
Winston W-Y
WW
Rada
Jody A
JA
D000818:Animals; D015153:Blotting, Western; D011508:Chondroitin Sulfate Proteoglycans / Q000172:deficiency / Q000502:physiology* / Q000648:ultrastructure; D005260:Female; D024022:Fibrillar Collagens / Q000378:metabolism* / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D007632:Keratan Sulfate / Q000172:deficiency / Q000502:physiology* / Q000648:ultrastructure; D000071234:Lumican; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009154:Mutation; D012590:Sclera / Q000378:metabolism* / Q000648:ultrastructure
D011508:Chondroitin Sulfate Proteoglycans; D024022:Fibrillar Collagens; C000604307:Lum protein, mouse; D000071234:Lumican; D007632:Keratan Sulfate