Fig. 5. Functional analysis of species differences in E4 sequence.

a, Hierarchical clustering of E4F2 sequences from seven vertebrates. Percentage nucleotide identity relative to mouse E4F2 is indicated in parentheses. b, Analysis of species differences in Sox11 activation of E4F2. Sox11 trans-activated the E4F2 sequence of five vertebrates (≥ 7.3 fold) and Xenopus (2.8 fold). In contrast, the activity of zebrafish E4F2, which is divergent in SB1 and SB2, was not activated by Sox11. c, Murinization (red uppercase nucleotides) of zebrafish SB2 (ZeE4F2-m2) partially rescued the loss of transactivation of zE4F2 by Sox11. d-e, Cell-autonomous rescue of mouse Fezf2 loss-of-function by zebrafish Fezf2 (ZeFezf2). In utero electroporation (IUE) of Fezf2^fl/fl neocortical wall at E12.5 with Cre and CRE-responsive Gfp plasmids. Fezf2-deficient L5 neurons do not form CS tract at P0 (d). Co-electroporation of a ZeFezf2 plasmid cell-autonomously rescued the formation of CS tract by Fezf2-deficient neurons (e). Errors bars represent s.e.m. One-tailed Student’s t-test; *P<0.05, **P<0.01, ***P<0.001. n = 4 per condition. Scale bar represents 200 µm.