Axons are reduced in frequency in the adult Tuba1a-Cre;Elp1^loxp/loxp small intestine. A, B, TrkB+ axons in the villi mucosa of adult proximal duodenum are reduced in frequency in the Elp1 cKO compared with control littermates; unpaired t test p = 0.0534, n = 7. C, D, Synapsin+ axons are more fragmented in the adult ileum villi mucosa in the Elp1 cKO compared with control littermates suggesting degeneration; unpaired t test p = 0.0012, n = 4. While both axon bundles (asterisk) and single axons (red arrow) are present in the control, in the mutant individual axons are prevalent (red arrows). E, Whole mount immunolabeling and clearing of proximal duodenum from adult control and Elp1 cKO reveal reduced villi mucosal innervation (Synapsin, magenta) in the cKO compared with the control. F, G, The density of Synapsin+ axons is reduced in the walls of the adult ileum smooth muscle in the cKO compared with littermate controls; unpaired t test p = 0.0447. See Extended Data Figure 3.1 for more details.