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Cyclic GMP-dependent protein kinase II is a molecular switch from proliferation to hypertrophic differentiation of chondrocytes.

ABSTRACT: The Komeda miniature rat Ishikawa (KMI) is a naturally occurring mutant caused by an autosomal recessive mutation mri, which exhibits longitudinal growth retardation. Here we identified the mri mutation as a deletion in the rat gene encoding cGMP-dependent protein kinase type II (cGKII). KMIs showed an expanded growth plate and impaired bone healing with abnormal accumulation of postmitotic but nonhypertrophic chondrocytes. Ex vivo culture of KMI chondrocytes reproduced the differentiation impairment, which was restored by introducing the adenovirus-mediated cGKII gene. The expression of Sox9, an inhibitory regulator of hypertrophic differentiation, persisted in the nuclei of postmitotic chondrocytes of the KMI growth plate. Transfection experiments in culture systems revealed that cGKII attenuated the Sox9 functions to induce the chondrogenic differentiation and to inhibit the hypertrophic differentiation of chondrocytes. This attenuation of Sox9 was due to the cGKII inhibition of nuclear entry of Sox9. The impaired differentiation of cultured KMI chondrocytes was restored by the silencing of Sox9 through RNA interference. Hence, the present study for the first time shed light on a novel role of cGKII as a molecular switch, coupling the cessation of proliferation and the start of hypertrophic differentiation of chondrocytes through attenuation of Sox9 function.

SUBMITTER: Chikuda H

PROVIDER: S-EPMC522991 | biostudies-literature | 2004 Oct

REPOSITORIES: biostudies-literature

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Cyclic GMP-dependent protein kinase II is a molecular switch from proliferation to hypertrophic differentiation of chondrocytes.

Chikuda Hirotaka H Kugimiya Fumitaka F Hoshi Kazuto K Ikeda Toshiyuki T Ogasawara Toru T Shimoaka Takashi T Kawano Hirotaka H Kamekura Satoru S Tsuchida Atsuko A Yokoi Norihide N Nakamura Kozo K Komeda Kajuro K Chung Ung-Il UI Kawaguchi Hiroshi H

Genes & development 20041001 19

The Komeda miniature rat Ishikawa (KMI) is a naturally occurring mutant caused by an autosomal recessive mutation mri, which exhibits longitudinal growth retardation. Here we identified the mri mutation as a deletion in the rat gene encoding cGMP-dependent protein kinase type II (cGKII). KMIs showed an expanded growth plate and impaired bone healing with abnormal accumulation of postmitotic but nonhypertrophic chondrocytes. Ex vivo culture of KMI chondrocytes reproduced the differentiation impai ...[more]

PMID: 15466490

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Project description:BackgroundAlthough transition from proliferation to hypertrophic differentiation of chondrocytes is a crucial step for endochondral ossification in physiological skeletal growth and pathological disorders like osteoarthritis, the underlying mechanism remains an enigma. This study investigated the role of the transcription factor CCAAT/enhancer-binding protein beta (C/EBPbeta) in chondrocytes during endochondral ossification.Methodology/principal findingsMouse embryos with homozygous deficiency in C/EBPbeta (C/EBPbeta-/-) exhibited dwarfism with elongated proliferative zone and delayed chondrocyte hypertrophy in the growth plate cartilage. In the cultures of primary C/EBPbeta-/- chondrocytes, cell proliferation was enhanced while hypertrophic differentiation was suppressed. Contrarily, retroviral overexpression of C/EBPbeta in chondrocytes suppressed the proliferation and enhanced the hypertrophy, suggesting the cell cycle arrest by C/EBPbeta. In fact, a DNA cell cycle histogram revealed that the C/EBPbeta overexpression caused accumulation of cells in the G0/G1 fraction. Among cell cycle factors, microarray and real-time RT-PCR analyses have identified the cyclin-dependent kinase inhibitor p57(Kip2) as the transcriptional target of C/EBPbeta. p57(Kip2) was co-localized with C/EBPbeta in late proliferative and pre-hypertrophic chondrocytes of the mouse growth plate, which was decreased by the C/EBPbeta deficiency. Luciferase-reporter and electrophoretic mobility shift assays identified the core responsive element of C/EBPbeta in the p57(Kip2) promoter between -150 and -130 bp region containing a putative C/EBP motif. The knockdown of p57(Kip2) by the siRNA inhibited the C/EBPbeta-induced chondrocyte hypertrophy. Finally, when we created the experimental osteoarthritis model by inducing instability in the knee joints of adult mice of wild-type and C/EBPbeta+/- littermates, the C/EBPbeta insufficiency caused resistance to joint cartilage destruction.Conclusions/significanceC/EBPbeta transactivates p57(Kip2) to promote transition from proliferation to hypertrophic differentiation of chondrocytes during endochondral ossification, suggesting that the C/EBPbeta-p57(Kip2) signal would be a therapeutic target of skeletal disorders like growth retardation and osteoarthritis.

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Cyclic GMP-dependent protein kinase II is a molecular switch from proliferation to hypertrophic differentiation of chondrocytes.

Publications

Cyclic GMP-dependent protein kinase II is a molecular switch from proliferation to hypertrophic differentiation of chondrocytes.

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