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Fig. 6
nlk and lef1 cooperatively regulate tbx6, and nlk regulates lef1 expression. (A-D) tbx6 expression at 60% epiboly, lateral view, dorsal to the right. A low dose (0.6 ng) of nlk MO has no effect on tbx6 expression (B, compare with wild type in A). 1 ng lef1 MO reduces tbx6 expression (C), and this effect is enhanced by co-injection of 0.6 ng nlk MO (D). (E-H) Expression of lef1 at shield stage, lateral view, dorsal to the right. lef1 is expressed at the margin in wild type (E), but is reduced in nlk MO (F). lef1 expression is dramatically elevated in tcf3a/tcf3b morphants (G) and in nlk/tcf3a/tcf3b MO embryos (H). (I-L) nlk or lef1 RNA rescues tbx6 expression in nlk morphants. nlk* RNA refers to the C387Y mutant. Co-injection of 200pg nlk RNA (K), but not nlk* RNA (J), restores tbx6 expression to levels similar to wild type (I). 100pg lef1 RNA (L) also rescues nlk morphants. Similarly, nlk RNA rescues normal lef1 expression (O, compare with wild type in M; arrowheads delineate the expression domain), whereas nlk* RNA (N) does not.