|
||
J. Cell Biol.,
Volume 142, Number 1, July 13, 1998 295-305

* Department of Medicine, Division of Endocrinology, University of Texas Health Science Center at San Antonio, San Antonio,
Texas 78284; Cumulative evidence indicates that osteoblasts and adipocytes share a common mesenchymal
precursor and that bone morphogenetic proteins
(BMPs) can induce both osteoblast and adipocyte differentiation of this precursor. In the present study, we
investigated the roles of BMP receptors in differentiation along these separate lineages using a well-characterized clonal cell line, 2T3, derived from the mouse
calvariae. BMP-2 induced 2T3 cells to differentiate into
mature osteoblasts or adipocytes depending upon culture conditions. To test the specific roles of the type IA
and IB BMP receptor components, truncated and constitutively active type IA and IB BMP receptor cDNAs
were stably expressed in these cells. Overexpression of
truncated type IB BMP receptor (trBMPR-IB) in 2T3
cells completely blocked BMP-2-induced osteoblast
differentiation and mineralized bone matrix formation.
Expression of trBMPR-IB also blocked mRNA expression of the osteoblast specific transcription factor, Osf2/ Cbfa1, and the osteoblast differentiation-related genes,
alkaline phosphatase (ALP) and osteocalcin (OC).
BMP-2-induced ALP activity could be rescued by
transfection of wild-type (wt) BMPR-IB into 2T3
clones containing trBMPR-IB. Expression of a constitutively active BMPR-IB (caBMPR-IB) induced formation of mineralized bone matrix by 2T3 cells without
addition of BMP-2. In contrast, overexpression of trBMPR-IA blocked adipocyte differentiation and expression of caBMPR-IA induced adipocyte formation in
2T3 cells. Expression of the adipocyte differentiation-related genes, adipsin and PPAR
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030; and § Genetics Institute, Cambridge, Massachusetts 02140
, correlated with the
distinct phenotypic changes found after overexpression of the appropriate mutant receptors. These results
demonstrate that type IB and IA BMP receptors transmit different signals to bone-derived mesenchymal progenitors and play critical roles in both the specification
and differentiation of osteoblasts and adipocytes.
This article has been cited by other articles:
|
|