title: PTHrP regulates growth plate chondrocyte differentiation and proliferation in a Gli3 dependent manner utilizing hedgehog ligand dependent and independent mechanisms.
abstract: Growth plate chondrocytes undergo a tightly regulated process of differentiation, allowing for the longitudinal growth of bones. Although it is known that parathyroid hormone related protein (PTHrP) and Indian hedgehog regulate the differentiation of growth plate chondrocytes, how these pathways interact to regulate chondrocyte development is not fully elucidated. We examined how the interaction between PTHrP and the hedgehog activated transcription factors, Gli2 and Gli3, regulates growth plate chondrocyte differentiation and proliferation. Analysis of fetal limbs showed that Gli2 is a negative regulator and Gli3 a positive regulator of type X collagen expression. Limb explant cultures showed that PTHrP treatment inhibited type X collagen expression and increased chondrocyte proliferation. This effect was substantially enhanced in Gli2-/- limbs, was blocked in Gli3-/- limbs, and was only partially inhibited by hedgehog ligand blockade. PTHrP negatively regulated Gli mediated transcription in cell cultures, and regulated the level of the repressor form of Gli3 in a PKA dependent manner. These results show that PTHrP regulates growth plate chondrocyte proliferation and differentiation in part through the activity of Gli3, suggesting a crucial role for Gli3 in growth plate chondrocyte development.
authors.affiliation: The Program in Developmental Biology of the Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Elaine
authors.initials: E
authors.lastname: Mau
authors.forename: Heather
authors.initials: H
authors.lastname: Whetstone
authors.forename: Chunying
authors.initials: C
authors.lastname: Yu
authors.forename: Sevan
authors.initials: S
authors.lastname: Hopyan
authors.forename: Jay S
authors.initials: JS
authors.lastname: Wunder
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Alman
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D019902:Chondrocytes / Q000378:metabolism / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006132:Growth Plate / Q000166:cytology / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D000075746:Zinc Finger Protein Gli2; D000074290:Zinc Finger Protein Gli3
chemical_list: C000618551:Gli2 protein, mouse; C465571:Gli3 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D009419:Nerve Tissue Proteins; D044162:Parathyroid Hormone-Related Protein; D000075746:Zinc Finger Protein Gli2; D000074290:Zinc Finger Protein Gli3; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases