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Fig. 4
The PBX-HOX and MEIS/PREP motifs of four enhancers are essential for their function.
Histograms for four elements, pax2.174 (A), meis2a.1042 (B), meis1.1705 (C) and foxd3.327 (D), showing the number of embryos with GFP positive cells in forebrain (fb), midbrain (mb), hindbrain (hb) and spinal cord (sc) when expressing wild-type (green), MEIS/PREP site mutant (blue) or PBX-HOX site mutant (red) constructs. Annotation displays p values for one-tailed paired t tests. All mutant constructs show a significant (student's t test p = <0.05) reduction in the number of embryos positive for hindbrain. Wild-type pax2.174 (E) drives expression in hindbrain and lens (green), whereas mutant constructs do not drive this pattern. Wild-type meis2a.1042 (F) drives expression in the central nervous system particularly the anterior hindbrain. Mutant constructs fail to recapitulate this expression. Wild-type meis1.1705 (G) drives expression in the hindbrain and spinal cord, but mutant constructs drive expression only in spinal cord. Wild-type foxd3.327 (H) drives expression in posterior hindbrain (green), but expression driven by constructs where either the MEIS/PREP (blue) or the PBX-HOX (red) motif is mutated is frequently ectopic in midbrain, anterior hindbrain and spinal cord.