Institute of Human Genetics,1 Department of Electron Microscopy,2 Department of Embryology, University of Göttingen, Göttingen, Germany3
Received 18 May 2004/ Returned for modification 3 June 2004/ Accepted 30 June 2004
The Sox genes define a family of transcription factors that play a key role in the determination of cell fate during development. The preferential expression of the Sox15 in the myogenic precursor cells led us to suggest that the Sox15 is involved in the specification of myogenic cell lineages or in the regulation of the fusion of myoblasts to form myotubes during the development and regeneration of skeletal muscle. To identify the physiological function of Sox15 in mice, we disrupted the Sox15 by homologous recombination in mice. Sox15-deficient mice were born at expected ratios, were healthy and fertile, and displayed normal long-term survival rates. Histological analysis revealed the normal ultrastructure of myofibers and the presence of comparable amounts of satellite cells in the skeletal muscles of Sox15/ animals compared to wild-type animals. These results exclude the role of Sox15 in the development of satellite cells. However, cultured Sox15/ myoblasts displayed a marked delay in differentiation potential in vitro. Moreover, skeletal muscle regeneration in Sox15/ mice was attenuated after application of a crush injury. These results suggest a requirement for Sox15 in the myogenic program. Expression analyses of the early myogenic regulated factors MyoD and Myf5 showed the downregulation of the MyoD and upregulation of the Myf5 in Sox15/ myoblasts. These results show an increased proportion of the Myf5-positive cells and suggest a role for Sox15 in determining the early myogenic cell lineages during skeletal muscle development.
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