Researchers identify defect that causes rare muscular d...( e mouse and patients the only defect i...)

e mouse and patients, the only defect is in glycosylation; all the other (dystrophin-glycoprotein complex) components are there," said Campbell. "This shows the importance of the dystroglycan link to the extracellular matrix."

To measure the effect of dystroglycan loss in a controlled way, Steven Moore, a professor of pathology at the University of Iowa, studied mice in which the dystroglycan gene was deleted selectively in brain. In these mice, they found a remarkable similarity to both the myd mouse and the patients brain abnormalities. The finding strengthened the groups hypothesis that dystroglycan is crucial for normal brain function by showing that its absence is sufficient to cause the neuronal migration defects seen in muscular dystrophy patients.

The findings of these two studies raise additional questions about the role of the dystrophin-glycoprotein complex in other developmental brain disorders that result in a smooth brain, some of which are caused by chemical or biological damage. For example, Campbell and his colleagues published a paper in the Journal of Cell Biology in 2001 showing that lymphocytic choriomeningitis virus can disrupt the dystroglycan link with the extracellular matrix. LCMV can infect humans, cross the placenta and infect the developing fetus. The infection produces developmental abnormalities remarkably similar to muscle-eye-brain disease and Walker-Warburg Syndrome.

Finally, the scientists have shown that mice without brain dystroglycan also have defects in an important process called long-term potentiation, which helps form long-term memory by strengthening the links between nerve cells. "This work demonstrates that dystroglycan has two roles in the brain: a developmental role and a synaptic role," said Campbell. "It is interesting because it opens up the whole area of learning and memory and raises questions about the link between neurobiology and muscle physiology."

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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
24-Jul-2002


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