p63 is a member of a highly conserved p53 transcription factor family, which regulates complex biological processes during development and tumorigenesis. Although extensive analyses TP63 gene using cultured cells of epidermal lineage led to acquisition of ample knowledge regarding its regulatory roles in epidermal differentiation, TP63 function in normal development of osteoblasts remains largely unknown. Thus, we examined expression levels of individual p63 isoforms during the course of MC3T3-E1 osteoblast differentiation using Western blot and RT-PCR assays. TAp63g expression was induced at the early phase of differentiation and continued throughout this process. TAp63a expression was induced at the late phase of differentiation paralleling with that of osteocalcin. In addition, despite the up regulation of DNp63 transcripts was also detected by RT-PCR, DNp63 isoform was undetectable by Western blot experiment. These results suggest that TAp63 isoforms may regulate osteoblast differentiation.
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