Figure 2. Histidine metabolic perturbations affect nerfin‐1 neuron‐to‐NB reversion.

1. Schematic depicting the metabolic reaction between histidine and its downstream metabolites histamine and 3‐methyl‐L‐histidine.
2. Concentration of histidine and 3‐methyl‐L‐histidine from whole Drosophila adults extracts measured by ¹H NMR after 3 days of feeding on either CDD or −his diet (n = 3, 3). Both compounds are reduced to below detection levels (< 0.3 mM) upon dietary his depletion.
3. Dietary supplementation of 3‐methyl‐L‐his for 4 days significantly increased adult nerfin‐1 clonal growth and rescued nerfin‐1 growth inhibition due to his dietary withdrawal (n = 18, 14, 7, 9).
4. Dietary supplementation of histamine does not significantly increase adult nerfin‐1 clone size, but can rescue nerfin‐1 clonal growth inhibition due to his dietary withdrawal (n = 42, 14, 23, 25).
5. Larval nerfin‐1 clonal growth is significantly decreased upon overexpression of HDC RNAi (n = 23, 36).
6. Schematic depicting stepwise neurons to NBs reversion in nerfin‐1 type I lineages where neurons express Elav, NBs express Dpn, and reverting neurons express both markers.
7. Hdc inhibition significantly reduced the percentage of Dpn⁺ NBs (n = 16, 17) and significantly increased the percentage of Elav⁺ neurons per clone (n = 16, 17).
8. Hdc^Ri overexpression reduced cellular growth of nerfin‐1 NBs (n = 17, 19) and neurons (n = 36, 19) measured as the ratio of nucleolus/nuclear volume.

Data information: In all graphs, the key indicates that green bars represent a significant increase (P < 0.05), red bars a significant decrease (P < 0.05), and grey bars no significant change (P > 0.05) in t‐tests with the relevant paired controls (black bar). In all graphs, error bars represent 1 standard error of the mean (SEM). FC, fold change. See also Figs EV2 and EV3.