Retinal ectopias and mechanically weakened basement membrane in a mouse model of muscle-eye-brain (MEB) disease congenital muscular dystrophy.
OBJECTIVE
Some forms of congenital muscular dystrophy are associated with cortical and retinal dysplasias. Protein O-mannose N-acetylglucosaminyltransferase 1 (POMGnT1) knockout mice, one of the mouse models of muscular dystrophy, exhibit a thinner retina with reduced density of retinal ganglion cells. This study is aimed to further characterize the knockout retina, with special emphasis on the inner limiting membrane, the basement membrane of the retina.


METHODS
Immunofluorescence staining and transmission electron microscopy were used to analyze the retinas. Atomic force microscopy was performed on the inner limiting membrane preparations to examine their mechanical properties.


RESULTS
The inner limiting membrane of the knockout mice exhibited frequent breaks with protrusions of the Müller glial processes and ectopic placement of retinal ganglion cells into the vitreous humor. Disruptions in inner limiting membrane integrity developmentally precede the cellular abnormalities. Regions of disrupted inner limiting membrane were also associated with molecular abnormalities of Müller glia that included diminished presence of the integral membrane proteins Kir4.1 (an inwardly rectifying potassium channel) and aquaporin-4. When measured with atomic force microscopy, the POMGnT1 knockout mouse inner limiting membrane (ILM) exhibited significantly reduced Young's modulus and is therefore mechanically weaker than the ILM from controls.


CONCLUSIONS
Deficiency of POMGnT1-mediated glycosylation of dystroglycan is implicated in reduced stiffness of the ILM. The weakened ILM results in the disruption of the membrane and subsequent reduction in retinal integrity.
Hu
Huaiyu
H
Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY, USA. huh@upstate.edu
Candiello
Joseph
J
Zhang
Peng
P
Ball
Sherry L
SL
Cameron
David A
DA
Halfter
Willi
W
D000015:Abnormalities, Multiple / Q000473:pathology*; D000818:Animals; D001485:Basement Membrane / Q000473:pathology* / Q000648:ultrastructure; D048430:Cell Shape; D002828:Choristoma / Q000150:complications / Q000473:pathology*; D004195:Disease Models, Animal; D055119:Elastic Modulus; D051379:Mice; D018345:Mice, Knockout; D009136:Muscular Dystrophies / Q000150:complications / Q000151:congenital* / Q000473:pathology; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism / Q000473:pathology; D012160:Retina / Q000201:enzymology / Q000473:pathology* / Q000648:ultrastructure; D012165:Retinal Ganglion Cells / Q000473:pathology / Q000648:ultrastructure; D013314:Stress, Mechanical; D014822:Vitreous Body / Q000473:pathology / Q000648:ultrastructure
D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase