Researchers in the 09 March 2006 issue of Nature (Vol. 440, No. 7081, pp 220-223) show how mutations in two different proteins can cause osteopetrosis, a rare congenital human disorder in which the bones become too dense.
Researchers knew that mutations in Ostm1 and ClC-7 can both cause the condition. Thomas Jentsch and his colleagues now show that in mice, Ostm1 forms a molecular complex with ClC-7, a membrane ion channel. This protein complex is trafficked to lysosomes, cellular compartments that degrade other molecules, and to the border of bone-degrading osteoclast cells.
Each component of this complex is unstable without the other, so mutations in either protein can disrupt bone resorption in osteopetrosis. The team found that mice lacking Ostm1, like those without ClC-7, also have a wider spectrum of problems characteristic of lysosomal storage disease, a group of lysosome disorders also seen in humans.
Thomas Jentsch (Centre for Molecular Biology, Hamburg, Germany)
(C) Nature press release.
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