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Reduced chondrocyte proliferation and chondrodysplasia in mice lacking the integrin-linked kinase in chondrocytes.

Terpstra L, Prud'homme J, Arabian A, Takeda S, Karsenty G, Dedhar S, St-Arnaud R - J. Cell Biol. (2003)

Bottom Line: This interaction is mediated by integrins and their cytoplasmic effectors, such as the integrin-linked kinase (ILK).In contrast, chondrocyte proliferation, assessed by BrdU or proliferating cell nuclear antigen labeling, was markedly reduced in the mutant growth plates.ILK inactivation in chondrocytes resulted in reduced cyclin D1 expression, and this most likely explains the defect in chondrocyte proliferation observed when ILK is inactivated in growth plate cells.

View Article: PubMed Central - PubMed

Affiliation: Genetics Unit, Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec, Canada H3G 1A6.

ABSTRACT
Chondrocyte proliferation and differentiation requires their attachment to the collagen type II-rich matrix of developing bone. This interaction is mediated by integrins and their cytoplasmic effectors, such as the integrin-linked kinase (ILK). To elucidate the molecular mechanisms whereby integrins control these processes, we have specifically inactivated the ILK gene in growth plate chondrocytes using the Cre-lox methodology. Mice carrying an ILK allele flanked by loxP sites (ILK-fl) were crossed to transgenic mice expressing the Cre recombinase under the control of the collagen type II promoter. Inactivation of both copies of the ILK-fl allele lead to a chondrodysplasia characterized by a disorganized growth plate and to dwarfism. Expression of chondrocyte differentiation markers such as collagen type II, collagen type X, Indian hedgehog and the PTH-PTHrP receptor was normal in ILK-deficient growth plates. In contrast, chondrocyte proliferation, assessed by BrdU or proliferating cell nuclear antigen labeling, was markedly reduced in the mutant growth plates. Cell-based assays showed that integrin-mediated adhesion of primary cultures of chondrocytes from mutant animals to collagen type II was impaired. ILK inactivation in chondrocytes resulted in reduced cyclin D1 expression, and this most likely explains the defect in chondrocyte proliferation observed when ILK is inactivated in growth plate cells.

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Normal differentiation of ILK-deficient chondrocytes. In situ hybridization of growth plate from control (fl/+, Cre, A, C, E, and G) or mutant (fl/fl, Cre, B, D, F, and H) E16.5 mouse femur. (A and B) Collagen type II (col II), antisense probe. (C and D) Collagen type X (col X), antisense probe. (E and F) Ihh, antisense probe. (G and H) PTHR1, antisense probe. The zone of expression is bracketed in E–H. Note that these markers of differentiation exhibit the same pattern of expression in control and mutant littermates. Background staining with sense probes was undetectable (not depicted). Bars, 100 μm.
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fig5: Normal differentiation of ILK-deficient chondrocytes. In situ hybridization of growth plate from control (fl/+, Cre, A, C, E, and G) or mutant (fl/fl, Cre, B, D, F, and H) E16.5 mouse femur. (A and B) Collagen type II (col II), antisense probe. (C and D) Collagen type X (col X), antisense probe. (E and F) Ihh, antisense probe. (G and H) PTHR1, antisense probe. The zone of expression is bracketed in E–H. Note that these markers of differentiation exhibit the same pattern of expression in control and mutant littermates. Background staining with sense probes was undetectable (not depicted). Bars, 100 μm.

Mentions: To confirm that chondrocyte differentiation was normal in the absence of ILK, we analyzed the expression of chondrocyte differentiation markers using in situ hybridization. The expression of collagen type II, a marker of immature, proliferating chondrocytes, and collagen type X, a marker of hypertrophic chondrocytes, was first monitored in embryonic long bones. At E16.5, chondrocytes from control (ILKfl/+,Cre) and mutant (ILKfl/fl,Cre) mice expressed α1 (II) and α1(X) collagen (Fig. 5Figure 5.


Reduced chondrocyte proliferation and chondrodysplasia in mice lacking the integrin-linked kinase in chondrocytes.

Terpstra L, Prud'homme J, Arabian A, Takeda S, Karsenty G, Dedhar S, St-Arnaud R - J. Cell Biol. (2003)

Normal differentiation of ILK-deficient chondrocytes. In situ hybridization of growth plate from control (fl/+, Cre, A, C, E, and G) or mutant (fl/fl, Cre, B, D, F, and H) E16.5 mouse femur. (A and B) Collagen type II (col II), antisense probe. (C and D) Collagen type X (col X), antisense probe. (E and F) Ihh, antisense probe. (G and H) PTHR1, antisense probe. The zone of expression is bracketed in E–H. Note that these markers of differentiation exhibit the same pattern of expression in control and mutant littermates. Background staining with sense probes was undetectable (not depicted). Bars, 100 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172728&req=5

fig5: Normal differentiation of ILK-deficient chondrocytes. In situ hybridization of growth plate from control (fl/+, Cre, A, C, E, and G) or mutant (fl/fl, Cre, B, D, F, and H) E16.5 mouse femur. (A and B) Collagen type II (col II), antisense probe. (C and D) Collagen type X (col X), antisense probe. (E and F) Ihh, antisense probe. (G and H) PTHR1, antisense probe. The zone of expression is bracketed in E–H. Note that these markers of differentiation exhibit the same pattern of expression in control and mutant littermates. Background staining with sense probes was undetectable (not depicted). Bars, 100 μm.
Mentions: To confirm that chondrocyte differentiation was normal in the absence of ILK, we analyzed the expression of chondrocyte differentiation markers using in situ hybridization. The expression of collagen type II, a marker of immature, proliferating chondrocytes, and collagen type X, a marker of hypertrophic chondrocytes, was first monitored in embryonic long bones. At E16.5, chondrocytes from control (ILKfl/+,Cre) and mutant (ILKfl/fl,Cre) mice expressed α1 (II) and α1(X) collagen (Fig. 5Figure 5.

Bottom Line: This interaction is mediated by integrins and their cytoplasmic effectors, such as the integrin-linked kinase (ILK).In contrast, chondrocyte proliferation, assessed by BrdU or proliferating cell nuclear antigen labeling, was markedly reduced in the mutant growth plates.ILK inactivation in chondrocytes resulted in reduced cyclin D1 expression, and this most likely explains the defect in chondrocyte proliferation observed when ILK is inactivated in growth plate cells.

View Article: PubMed Central - PubMed

Affiliation: Genetics Unit, Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec, Canada H3G 1A6.

ABSTRACT
Chondrocyte proliferation and differentiation requires their attachment to the collagen type II-rich matrix of developing bone. This interaction is mediated by integrins and their cytoplasmic effectors, such as the integrin-linked kinase (ILK). To elucidate the molecular mechanisms whereby integrins control these processes, we have specifically inactivated the ILK gene in growth plate chondrocytes using the Cre-lox methodology. Mice carrying an ILK allele flanked by loxP sites (ILK-fl) were crossed to transgenic mice expressing the Cre recombinase under the control of the collagen type II promoter. Inactivation of both copies of the ILK-fl allele lead to a chondrodysplasia characterized by a disorganized growth plate and to dwarfism. Expression of chondrocyte differentiation markers such as collagen type II, collagen type X, Indian hedgehog and the PTH-PTHrP receptor was normal in ILK-deficient growth plates. In contrast, chondrocyte proliferation, assessed by BrdU or proliferating cell nuclear antigen labeling, was markedly reduced in the mutant growth plates. Cell-based assays showed that integrin-mediated adhesion of primary cultures of chondrocytes from mutant animals to collagen type II was impaired. ILK inactivation in chondrocytes resulted in reduced cyclin D1 expression, and this most likely explains the defect in chondrocyte proliferation observed when ILK is inactivated in growth plate cells.

Show MeSH
Related in: MedlinePlus