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. 2013 May 6;8(5):e63721. doi: 10.1371/journal.pone.0063721

Figure 7. Model of timing of SM differentiation in the developing ureter.

Figure 7

(A) Activation of the expression of SM genes correlates with the downregulation of Sox9. (B) In vivo and in vitro data suggest that prolonged expression of Sox9 affects the transcriptional activation of SM genes but not the expression of Myocd. (C) Quantitative analysis of transcripts of Sox9, Myocd and SM markers in E16.5 wild-type and Tbx18Cre/+;HprtSox9/+ (prolonged Sox9) dissected ureters. mRNA transcripts were normalized to glyceraldehyde 3-phosphate dehydrogenase (Gadph) (n = 7, mean ± SEM). (D) The upper panel shows the correlation between the status of ureteric mesenchymal cell differentiation, and the expression of the SM regulatory factors Tshz3, Sox9 and Myocd. The middle panel schematizes the expression levels of these regulatory genes during ureter development. The bottom panel summarizes the molecular interactions and the molecular switch that precedes the expression of SM genes. In the undifferentiated mesenchyme Tshz3 and Sox9 are required for the expression of Myocd. SM progenitors express TSHZ3, SOX9 and MYOCD. Downregulation of SOX9 allows expression of SM genes, thus, a “functional switch” from embryonic ureteric tube to the contractile ureter.