Heterodimers between TCF3 and tissue-specific basic helix-loop-helix (bHLH) proteins play major roles in determining tissue-specific cell fate during embryogenesis, like muscle or early B-cell differentiation. Dimers bind DNA on E-box motifs: 5-CANNTG-3. Binds to the kappa-E2 site in the kappa immunoglobulin gene enhancer.
