Fig. 6

Deletion of TR1 significantly suppresses the ectopic expression of tbx6 caused by the loss of function of ripply1 in zebrafish. (A) Fluorescence in situ hybridization to examine the distribution of tbx6 nascent transcripts (green) and Tbx6 protein (magenta) in wild- type (n=3) and ripply1^−/−; ripply2^−/− (n=3) embryos at the 10-somite stage. Dorsal views of flat-mounted embryos. (B) Anterior expansion of tbx6 expression in ripply1^−/− embryos was substantially suppressed in tbx6^ΔTR1/ΔTR1; ripply1^−/− embryos at the 3- to 5-somite stage. (C) Schematic illustrations of Ripply-mediated synchronous regression of the expression domains of Tbx6 protein and tbx6 transcription in the anterior PSM. Transcription of zebrafish tbx6 is maintained by Tbx6 itself through a single enhancer: TR1. Ripply-mediated degradation of Tbx6 protein leads to transcriptional termination of tbx6 in the PSM. Scale bars: 200 μm in A; 100 μm in B.