(A) Sequence of the human TBXT binding site (T-box) using JASPAR.
(B) FIMO output with location of the T-box, statistical significance, and matched sequence within the enhancer elements.
(C) Schematic depiction of the wildtype human enhancer elements with the TBXT binding site/T-box (pink box) and the enhancer elements without the respective T-box sites (ΔTbox). All human enhancer elements are depicted in the reverse complement direction.
(D-I) Injection of the wildtype enhancer elements hs_T3 (D), hs_C (F), and hs_I (H) as reporter constructs results in mApple fluorophore expression in the notochord at 48 hpf, whereas injection of hs_T3ΔTbox (E) and hs_IΔTbox (I) show complete loss of notochord expression (asterisks in E,I) in comparison to hs_CshortΔTbox (G), which has residual reporter activity even without the T-box. Arrowheads (D-I) mark EGFP expression in the pineal gland from the transgenesis marker exorh:EGFP. Scale bar in D: 0.5 mm, applies to D-I.