Picking a bone with the matrix
Contrary to common perception, bones are dynamic tissues in which some cells, the osteoblasts, contribute to bone deposition, and others, the osteoclasts, promote bone resorption. Toggling the balance between these opposing activities results in bone formation and remodeling during growth and regeneration. This balance would seem to be upset in people with the 'vanishing bone' syndromes - a group of disorders where the affected bones are excessively resorbed and destroyed (osteolysis). Other aspects of these diseases include erosion of the joints between the phalanxes, reminiscent of rheumatoid arthritis. Until now, the cause of vanishing bone syndromes was unknown.
John Martignetti (of Mount Sinai School of Medicine, New York) and colleagues now report the cause of one form of inherited osteolysis: mutations in the gene encoding a matrix metalloproteinase, which belongs to a large family of proteases that degrade components of the extra-cellular matrix (ECM) (Nature Genetics, Vol. 28, No. 3, 01 July 2001). In bones, the ECM is thought to be essential for proper differentiation of the surrounding cell types, such as osteoblasts and osteoclasts, and may thus affect the equilibrium between bone formation and resorption. Diminished ECM, however, is thought to underlie osteolysis, and so mutations in a gene whose product breaks down the extracellular matrix comes as something of a surprise.
As discussed in an accompanying News & Views article by Thiennu Vu (of University of California, San Francisco, California), this study should inspire caution when designing therapeutic approaches to disorders caused by the disruption of the ECM.
Dr. John Martignetti
Mount Sinai School of Medicine
New York, New York, USA.
Telephone: +1 (212) 659-6744
Fax: +1 (212) 849-2638
Dr. Thiennu Vu
University of California
San Francisco, California, USA.
Telephone: +1 (415) 206-5908
Fax: +1 (415) 206-4123
(C) Nature Genetics press release.
Message posted by: Trevor M. D'Souza