Nature Genetics
30, 421 - 425 (2002)
Published online: 4 March 2002; | doi:10.1038/ng850
Tenascin-X deficiency mimics Ehlers-Danlos syndrome in mice through alteration of collagen depositionJau Ren Mao1, Glen Taylor1, Willow B. Dean1, 3, Diane R. Wagner2, Veena Afzal3, Jeffrey C. Lotz2, Edward M. Rubin3
& James Bristow1, 31
Department of Pediatrics, University of California, Laurel Heights Campus, 3333 California Street, Box 1245, San Francisco, California 94118, USA. 2
Department of Orthopedic Surgery, University of California, Laurel Heights Campus, 3333 California Street, Box 1245, San Francisco, California 94118, USA. 3
Genome Sciences, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
Correspondence should be addressed to James Bristow jbristow@pedcard.ucsf.eduTenascin-X is a large extracellular matrix protein of unknown function1,
2,
3. Tenascin-X deficiency in humans is associated with Ehlers−Danlos syndrome4,
5, a generalized connective tissue disorder resulting from altered metabolism of the fibrillar collagens6. Because TNXB is the first Ehlers−Danlos syndrome gene that does not encode a fibrillar collagen or collagen-modifying enzyme7,
8,
9,
10,
11,
12,
13,
14, we suggested that tenascin-X might regulate collagen synthesis or deposition15. To test this hypothesis, we inactivated Tnxb in mice. Tnxb-/- mice showed progressive skin hyperextensibility, similar to individuals with Ehlers−Danlos syndrome. Biomechanical testing confirmed increased deformability and reduced tensile strength of their skin. The skin of Tnxb-/- mice was histologically normal, but its collagen content was significantly reduced. At the ultrastructural level, collagen fibrils of Tnxb-/- mice were of normal size and shape, but the density of fibrils in their skin was reduced, commensurate with the reduction in collagen content. Studies of cultured dermal fibroblasts showed that although synthesis of collagen I by Tnxb-/- and wildtype cells was similar, Tnxb-/- fibroblasts failed to deposit collagen I into cell-associated matrix. This study confirms a causative role for TNXB in human Ehlers−Danlos syndrome and suggests that tenascin-X is an essential regulator of collagen deposition by dermal fibroblasts.
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