Schäfer, M., Rembold, M., Wittbrodt, J., Schartl, M., and Winkler, C. (2005) Medial floor plate formation in zebrafish consists of two phases and requires trunk-derived Midkine-a. Genes and Development. 19(8):897-902.
The medial floor plate (MFP) organizes the specification of neurons and outgrowth of axons in the ventral spinal cord of vertebrates. We show that the growth factor Midkine-a, expressed in the paraxial mesoderm, is required for formation of the MFP in zebrafish. Our epistatic analyses demonstrate that development of MFP comprises two independent sequential phases. Following initial MFP induction in the gastrula organizer, Midkine-a regulates allocation of MFP cells during subsequent development. Thus in zebrafish, trunk-derived signals are required for complete MFP formation from a common pool of organizer-derived midline precursor cells.