Fig. 4. Mesencephalic ventral midline cells with FP-like marker expression have mesDA progenitor characteristics. (A-C) Co-expression of FP4 and Lmx1a in the rat ventral mesencephalon at E14.5. (D) Virtually all of the neural progenitor cells at the ventral midline of the mesencephalon express Lmx1a. NG2 marks blood vessels. (E,F) Ngn2 and Mash1 are expressed in FP4⁺ cells in the rat mesencephalon. (G,H) FP cells of the E11.5 rat mesencephalon without proneural gene expression have mesDA characteristics. (I-Q) Ngn2, Mash1, Lmx1a and Dll1 are selectively expressed in mesencephalic FP cells, but not in caudal FP cells of E11.5 mouse embryos. Lmx1b is expressed in midline cells at all AP locations. Mes, mesencephalon; Met, metencephalon; Nuc, nuclear stain; SC, spinal cord.