The Indian Hedgehog - PTHrP System in Bone Development
205
to be expressed after birth and regulate postnatal bone growth as well as
fracture repair. This demonstrates that the analysis of embryonic signaling systems will not only result in an understanding of embryonic bone
development, but will also have impact on possible forms of treatment
for postnatal bone diseases and bone fractures.
It is expected that the IhhlPTHrP pathway is only part of a complex
signaling system. Intensive studies are necessary to identify the other
players of this signaling network, to analyze their function and to study
their interactions. BMPs are one group of factors that have been anticipated to playa crucial role in regulating bone formation and several
lines of evidence indicate that in addition to inducing the onset of bone
formation, BMPs might act at several stages during chondrocyte differentiation. Activation of BMP signaling has been shown to result in
similar phenotypes as those seen after overexpression of Ihh. At least
two BMP genes, BMP2 and BMP4, are good candidates to be directly
regulated by Ihh. In addition, expression analyses of two BMP antagonists, Noggin and Chordin, indicate that BMP signaling during bone
development might interact with that of the IhhlPTHrP system. However, the exact interaction of the two signaling pathways requires further
analysis.
References
Amizuka N, Warshawsky H, Henderson JE, Goltzman D, Karaplis AC (1994)
Parathyroid hormone-related peptide-depleted mice show abnormal epiphyseal cartilage development and altered endochondral bone formation. J
Cell BioI 126:1611-1623
Bitgood MI, McMahon AP (1995) Hedgehog and Bmp genes are coexpressed
at many diverse sites of cell-cell interaction in the mouse embryo. Dev Bioi
172:126-138
Bolander ME (1992) Regulation of fracture repair by growth factors. Proc Soc
Exp Bioi Med 200: 165-170
Capdevila J, Johnson RL (1998) Endogenous and ectopic expression of noggin
suggests a conserved mechanism for regulation of BMP function during
limb and somite patterning. Dev Bioi 197:205-217
Chung VI, Lanske B, Lee K, Li E, Kronenberg H (1998) The parathyroid hormone/parathyroid hormone-related peptide receptor coordinates endochon-
205
to be expressed after birth and regulate postnatal bone growth as well as
fracture repair. This demonstrates that the analysis of embryonic signaling systems will not only result in an understanding of embryonic bone
development, but will also have impact on possible forms of treatment
for postnatal bone diseases and bone fractures.
It is expected that the IhhlPTHrP pathway is only part of a complex
signaling system. Intensive studies are necessary to identify the other
players of this signaling network, to analyze their function and to study
their interactions. BMPs are one group of factors that have been anticipated to playa crucial role in regulating bone formation and several
lines of evidence indicate that in addition to inducing the onset of bone
formation, BMPs might act at several stages during chondrocyte differentiation. Activation of BMP signaling has been shown to result in
similar phenotypes as those seen after overexpression of Ihh. At least
two BMP genes, BMP2 and BMP4, are good candidates to be directly
regulated by Ihh. In addition, expression analyses of two BMP antagonists, Noggin and Chordin, indicate that BMP signaling during bone
development might interact with that of the IhhlPTHrP system. However, the exact interaction of the two signaling pathways requires further
analysis.
References
Amizuka N, Warshawsky H, Henderson JE, Goltzman D, Karaplis AC (1994)
Parathyroid hormone-related peptide-depleted mice show abnormal epiphyseal cartilage development and altered endochondral bone formation. J
Cell BioI 126:1611-1623
Bitgood MI, McMahon AP (1995) Hedgehog and Bmp genes are coexpressed
at many diverse sites of cell-cell interaction in the mouse embryo. Dev Bioi
172:126-138
Bolander ME (1992) Regulation of fracture repair by growth factors. Proc Soc
Exp Bioi Med 200: 165-170
Capdevila J, Johnson RL (1998) Endogenous and ectopic expression of noggin
suggests a conserved mechanism for regulation of BMP function during
limb and somite patterning. Dev Bioi 197:205-217
Chung VI, Lanske B, Lee K, Li E, Kronenberg H (1998) The parathyroid hormone/parathyroid hormone-related peptide receptor coordinates endochon-