Cyclic GMP-dependent protein kinase II is a molecular switch from proliferation to hypertrophic differentiation of chondrocytes.
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.
Chikuda
Hirotaka
H
Department of Sensory and Motor System Medicine, Faculty of Medicine, University of Tokyo, Bunkyo, Tokyo 113-8655, Japan.
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
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D019902:Chondrocytes / Q000502:physiology*; D062967:Cyclic GMP-Dependent Protein Kinase Type II; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology*; D017931:DNA Primers; D005260:Female; D006132:Growth Plate / Q000166:cytology; D006609:High Mobility Group Proteins / Q000502:physiology; D008297:Male; D051381:Rats; D055758:SOX9 Transcription Factor; D014157:Transcription Factors / Q000502:physiology
D017931:DNA Primers; D006609:High Mobility Group Proteins; D055758:SOX9 Transcription Factor; D014157:Transcription Factors; D062967:Cyclic GMP-Dependent Protein Kinase Type II; D017869:Cyclic GMP-Dependent Protein Kinases; C569732:Prkg2 protein, rat