Hi everyone,

An article has just appeared in the scientific journal Nature which
reports some very interesting results on the dysferlin protein. The
researchers created a breed of mouse which lacks dysferlin, and
compared the muscles of the dysferlin-deficient mouse to a type of
mouse that lacks dystrophin (the mdx mouse, which is an animal model
of Duchenne muscular dystrophy).

They made two major findings.

1) In the mdx mouse, the muscle cells were easily damaged by
exercise, much more so than in the normal mouse. This was known
already, but the dysferlin-deficient mouse's muscles weren't any
more susceptible to damage than those of the normal mouse. So
dysferlin isn't needed to protect the muscles from damage.

2) The researchers tested the ability of muscles to repair damage in
the cell membrane by using a laser to create damage in muscle cells
on a microscope slide. In the normal mouse, the muscle cells could
quickly (within a minute or so) repair holes in the cell membrane if
there was calcium present outside the cell. [normally there is very
little calcium inside muscle cells, so the cells seem to use high
levels of calcium leaking into the cell as a signal that the cell
membrane is damaged and needs to be repaired]. In the muscle cells
from the mdx mouse, the repair mechanism worked the same as in the
normal mice. In the dysferlin-deficient mouse, the repair mechanism
didn't work.

So:
Normal: muscle cells not easily damaged, and can repair themselves.
Mdx (no dystrophin): repair mechanism ok, but cells easily damaged.
eventually the damage overwhelms the repair mechanism.
No dysferlin: cells not easily damaged, but can't repair themselves
when they are damaged. Eventually damage builds up.

It's not known exactly how the details of the repair mechanism work,
or the exact role that dysferlin plays. But the experiments in this
paper do show that dysferlin is needed for the process to work

the complete reference:
Defective membrane repair in dysferlin-deficient muscular dystrophy
DIMPLE BANSAL, KATSUYA MIYAKE, STEVEN S. VOGEL, SÉVERINE GROH, CHIEN-
CHANG CHEN, ROGER WILLIAMSON, PAUL L. MCNEIL & KEVIN P. CAMPBELL
Nature 423, 168–172 (2003); doi:10.1038/nature01573

web page with a summary:
http://www.nature.com/nature/links/030508/030508-1.html

You need a subscription to read the full article on the nature
site. If you don't have access and want to read the article, write
me.

Brad