Figure 1

Schematic representation of the GI tract in mammalians and zebrafish. (A) Schematic representation of the layers present in the GI tract of mammalians and zebrafish. Zebrafish lack the muscularis mucosa and submucosal plexus. In addition, the enteric neurons are not organized in ganglia, but rather as individual cells (Wallace and Pack, 2003). (B) Schematic representation of the mammalian (human) and the zebrafish digestive system. While the human GI tract is divided in stomach, duodenum, jejenum, ileum and colon, the GI tract of the zebrafish is traditionally subdivided in three major components, rostral intestinal bulb, mid intestine and posterior segment (Wang et al., 2010). A new division based on conserved transcriptional profiles has also been proposed, which is depicted by color alterations and labels in regular font (Lickwar et al., 2017). Note that boundaries between sections should not necessarily be considered discrete. (C) Schematic representation of ENS development in zebrafish showing that the NCCs depicted in green are first detected in the developing intestine around 32–36 h post-fertilization (hpf). NCCs migrate in two parallel chains caudally, between 36 and 66–72 hpf. Starting rostrally, the NCCs start to migrate laterally to form a network. At 4 days post-fertilization (dpf) the ENS network has been formed around the total length of the intestine. (D) Schematic representation of ENS development in mammals. Vagal NCCs colonize the foregut at embryonic day (E)7-E9.5 in mice and gestational week (GW) 4 in humans. From E10.5, NCCs migrate caudally in various multicellular strands.