- Endothelin-converting enzyme-1 (ECE-1) is a downstream target of the homeobox transcription factor Nkx2-5. Funke-Kaiser, H., Lemmer, J., Langsdorff, C.V., Thomas, A., Kovacevic, S.D., Strasdat, M., Behrouzi, T., Zollmann, F.S., Paul, M., Orzechowski, H.D. FASEB J. (2003)