Role of bHLH transcription factor DEC1 on chondrogenic differentiation

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We cloned human and mouse DEC1 genes and determined an entire nucleotide sequence of the genes including 3 kb of the upstream region. The DEC1 genes consisted of 5 exons and 4 introns, and there were several sequence elements including 3 E-boxes in the upstream region. There was no TATA box, but several GC boxes were identified in the promoter region :We constructed a series of deletion constructs of different lengths of the DEC1 promoter fused to the luciferase reporter gene and transfected them into several types of cells. The results showed that at least 260 bp region upstream from the transcription start site had significant promoter activity in the several cells. Further, when several expression vectors encoding CLOCK, BMAL1, MyoD and HlF1 were co-transfected into the cells,. the promoter activity of the DEC1 gene was increased.Expression pattern of DEC1 mRNA was also examined by Northern blot and RT-PCR analyses. DEC1 mRNA was expressed almost all of cells and tissues examined, and the expression was induced by the addition of cAMP to the cells. Overexpression of DEC1 gene in ATDC5 cells induced chondrogenic differentiation of the cell.