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Fig. 8. Model of E-cadherin regulation in the cadherin cluster. Parts of the P- and
E-cadherin locus are shown. Exons are represented by vertical black bars and
numbers, DHSs by vertical arrows, transcription start sites by small
horizontal arrows, E-boxes by red boxes and sequences with enhancing
activities by green boxes (intron 1-enhancer represented by unlabeled box).
alt., sequences that mediate alternative, intron 2-independent gene activation
in late embryogenesis; brain, sequences that contribute to brain-specific
expression; endoderm, sequences required for endoderm-specific expression;
enh., sequences that generally enhance transcription; sil., brain-specific
silencer that restricts gene activity to E-cadherin expression domains;
tse1-4, tissue-specific enhancers, including elements for ectoderm-specific
expression. The presence of a locus control region (LCR) is not yet proven and
the precise positions of `sil.', `tse1-4' and `alt.' are unknown. Elements
that contribute to expression in yolk sac must be located outside of intron 2.
E-boxes are required for downregulation of the gene (red arrow), whereas
elements in intron 2 activate the locus (green arrows). The postulated LCR
might influence gene activity for proper activation and downregulation (purple
arrow).
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