In healthy patients dystrophin is localised just under the cell
membrane. It is absent in the Duchenne patient. The pathogenesis of
the disease is unknown. Since the discovery and cloning of the
dystrophin gene, potential gene therapy is the object of intense
research. The group of the Institut Gustave Roussy in Villejuif
(France) has succeeded in inserting a large part of the dystrophin
cDNA into an adenovirus. The resulting protein has been called "mini-
dystrophin" and is stably expressed in transfected muscle fibres of
young mice. It is essential to test if minidystrophin can confer a
functional recovery where it is expressed. The possibility to sustain
forced elongations during contraction will be critical test for the
evaluation of the functional recovery. A study has been conducted in
the Department of Physiology in Brussels (Belgium)
which shows that fast skeletal muscles from mdx mice are very
sensitive to mechanical stress, a finding which points towards a
genuine membrane weakness in dystrophin lacking fibres. It is also
tested if the over-expression of utrophin can substitute for dystrophin. The group of the II Institute of Physiology in Heidelberg (Germany)has shown
that native sarcolemma vesicles obtained from mdx muscle fibres are
mechanically less stable compared to normal controls. Similar experiments will be carried out on minidystrophin containing membrane vesicles and the tensile
strength of these minidystrophin membranes will be determined.
Given the high
efficiency of the minidystrophin transfection with the adenoviral
carrier, this method is likely to become the first realistic gene
therapy in Duchenne patients. However, before investing in
developing this therapy, it is essential to know if minidystrophin
can functionally replace dystrophin. The project is suitably designed
to bring the answer.