FIGURE 7

Elevated Hoxb5b abrogates the expansion capacity of enteric NCC-derived neuronal lineage. (A,B) By 63 hpf, sox10:GFP ⁺ embryos immunolabeled for Phox2b show cells which have partially migrated along the gut in both control and vp16-hoxb5b injected animals. Gut tract outlined with white dashes. (C) No changes were found in the number of GFP⁺ NCC lineage or Phox2b⁺ cells along the gut between control embryos (n = 6) and those overexpressing vp16-hoxb5b (n = 6) (Enteric GFP⁺: p = 0.2619; Enteric Phox2b⁺: p = 0.7896). (D) Assessment of fraction of GFP⁺ cells which are also positive for Phox2b⁺ restricted to the gut axis from the same animals in (C), as a measure of NCC which have initiated their differentiation programs shows the fraction of Sox10⁺ lineage cells which have turned on Phox2b expression is unchanged following elevated Hoxb5b (p = 0.1253). (E) Summary of the number of Phox2b⁺ cells for either WT control embryos or embryos injected with 15 pg vp16-hoxb5b mRNA as a function of age from animals used throughout this study. The trend shows while the number of Phox2b⁺ cells initially is greater than WT, eventually the WT Phox2b⁺ numbers continue to increase with the Phox2b⁺ population in Hoxb5b elevated embryos remains flat. Error bars reflect ± one standard deviation. (F) Graphical Model of the role of Hoxb5b in NCC development, such that early Hoxb5b expression grossly expands NCC numbers, while later in development Hoxb5b suppresses NCC enteric expansion. Scale bar (A): 100 μm.