Fig. 2. Identification of the functional E-box motifs responsible for the somite-specific activation of Epha4. (A) Sequence of the 630 bp Epha4 somite enhancer (core enhancer) region. The four indicated fragments (fragment 1-4) represent deleted sequences from the core enhancer region. The results of transgenic analyses using these deleted constructs are shown in parentheses. (B) Sequence alignment of somite enhancer regions (fragment 2 and fragment 3) of mouse Epha4 with the corresponding regions of human Epha4. The mutations introduced in each E-box and the results of the subsequent transgenic analyses are shown. (C) Schematic representation of artificially constructed enhancers, containing six E-box motif repeats. (D) The artificial enhancers were cloned upstream of a lacZ reporter vector and the results of the subsequent transgenic analyses (representative images are shown) are indicated in parentheses. For the [E2]₆-lacZ artificial enhancer, no somite expression was observed among the 11 transgene-positive embryos. Blue letters indicate putative E-box motifs.