Abstract:
L-Sox5 is a member of sex-determining region
Y-type high mobility group box (SOX) family of transcription
factors. We assessed the effects of retroviral
overexpression of L-Sox5 on chondrocyte differentiation
using the clonal murine cell line ATDC5. We observed a
temporal-restricted expression pattern of L-Sox5 in insulininduced
ATDC5 cells differentiating toward chondrocyte
lineage. The protein expression levels of L-Sox5 showed a
drastic decrease in contrast to unaltered mRNA levels
during differentiation. L-Sox5 delayed the differentiation
of ATDC5 cells as evidenced by Alcian blue staining for
proteoglycan synthesis. The mRNA levels of chondrocyte
and hypertrophic/osteoarthritic markers were markedly
decreased or delayed in L-Sox5 overexpressing cells.
L-Sox5 abrogated the promoter activity of Runx2. These
results suggest that L-Sox5 protein expression may
diminish along with the progress of chondrogenic differentiation. L-Sox5 may act as a negative regulator if
expressed aberrantly at least in part by regulating the
critical fate of chondrogenesis.
