Figure 8
Differential Acan expression achieved by unique combinations of PAX1/PAX9, SOX9, and SOX5/SOX6. (a) The mouse UE sequence from 301 to 355 is shown. Underlined and boxed letters in the sequence are the SOX9-binding sites and the PAX1-binding site, respectively, as revealed by gel shift assays in Supplementary Fig. 6. (b) A proposed model for the transcriptional regulation of Acan mediated by the interaction of PAX1/9, SOX9, and SOX5/6 with the Acan enhancers is shown. During vertebral column development, UE weakly activates Acan transcription in the OAF (I), which expresses PAX1/9 and SOX9; moderately in the IAF (II), which expresses PAX1/9 and SOX9/5/6; and strongly in the cartilaginous VB (III), which expresses SOX9/5/6. In parallel, I12E activates Acan transcription weakly in the OAF and IAF, which express PAX1/9. Details are discussed in the text. Ca, cartilage; IAF, inner annulus fibrosus; IM, intervertebral mesenchyme; IVD, intervertebral disc, Nc, notochord; NP, nucleus pulposus; OAF, outer annulus fibrosus; VB, vertebral body. Scale bar, 100 μm.
