Int. J. Dev. Biol. 52: 323 - 332 (2008)
doi: 10.1387/ijdb.072490gh
© UBC Press

Loss of Sox9 function results in defective chondrocyte differentiation of mouse embryonic stem cells in vitro

Gunnar Hargus1, Ralf Kist2,3, Jan Kramer1,4, Daniela Gerstel1, Angela Neitz1, Gerd Scherer2 and Jürgen Rohwedel*,1

1Dept. of Medical Molecular Biology, University of Lübeck, Lübeck, 2Institute of Human Genetics and Anthropology, University of Freiburg, Freiburg, 3Institute of Mammalian Genetics, GSF-National Research Center for Environment and Health, Neuherberg and 4Medical Clinic I, University of Lübeck, Lübeck, Germany

ABSTRACT The transcription factor Sox9 plays an important role during chondrogenesis. After early conditional inactivation of Sox9 in mesenchymal limb bud cells of mice, mesenchymal condensations as well as cartilage and bone are completely absent in the developing limbs. We analyzed chondrogenic differentiation of Sox9-/- mouse embryonic stem cells in vitro, using two clones with different targeted mutations. We found that the development of mature and hypertrophic chondrocytes is completely inhibited in the absence of Sox9 confirming that Sox9 is required for the formation of cartilage. In contrast, Sox9+/- mouse embryonic stem cells showed continous but reduced differentiation into mature chondrocytes. Interestingly, the formation of early chondrogenic condensations expressing characteristic marker genes such as scleraxis, Sox5 and Sox6 was not inhibited in the absence of Sox9 in vitro. Thus, we propose that the earliest step of chondrogenesis could be regulated by a non cell-autonomous function of Sox9.

Keywords:

chondrogenesis, in vitro differentiation, mesenchymal condensations, Sox9

*Corresponding author e-mail: rohwedel@molbio.uni-luebeck.de