Figure 4.

MYCN overexpression increases neuroblast proliferation in vivo. A, Migrating neural crest cells were transfected by electroporation with Pb plasmid and piggybac transposon vectors for GFP (control) or GFP and MYCN (MYCN). At E5, proliferating cells were labeled by an EdU pulse and, after fixation of the embryo, cross sections from the GFP-expressing transfected area were triple-immunostained for EdU, Th, and GFP. B, Quantification of the percentage of EdU-labeled GFP⁺/Th⁺ neuroblasts reveals a significant increase in MYCN-expressing cells (mean ± SEM; n = 7; **p < 0.01). Arrows point to GFP⁺/Th⁺ neuroblasts with increased EdU-labeling in MYCN transfected cells.