- The nuclear receptor homologue Ftz-F1 and the homeodomain protein Ftz are mutually dependent cofactors. Guichet, A., Copeland, J.W., Erdélyi, M., Hlousek, D., Závorszky, P., Ho, J., Brown, S., Percival-Smith, A., Krause, H.M., Ephrussi, A. Nature (1997)