Figure 1

Characterization of the dI1 enhancer. The EdI1 enhancer element was cloned upstream of Cre recombinase and electroporated with (A) a conditional alternating mCherry/GFP (CAGG-loxP-mCherry-loxP-GFP) or (B, C) a conditional nuclear GFP (CAGG-loxP-STOP-loxP-nGFP) plasmid. Chick embryos were electroporated at stage 16 and fixed at stage 23 (B, C) or stage 26 (A). Cross-sections of electroporated neural tube were stained with dI-specific antibodies (B, C). (A) The use of the alternating mCherry/GFP allows the simultaneous detection of the electroporated cells (expressing mCherry) and cells that express the EdI1 enhancer (expressing GFP). Most of the cells, along the entire dorsal/ventral levels, express mCherry, while a subpopulation of dorsally located cells expresses GFP. (B) Cross-sections of electroporated neural tube were stained with Isl1 and Lhx2/9 antibodies. Nuclear GFP (nGFP)-expressing neurons are Lhx2/9⁺/Isl1^-. (C) Cross-sections of electroporated neural tube were stained with Isl1 and Lhx1/5 antibodies. nGFP expressing neurons are Lhx2/9⁺/Lhx1/5^-. The boxed areas in (B, C) are represented as enlargements in their different channels at the bottom of each panel. The arrows point to the nGFP-expressing cells. Scale bars: 50 μm.