Extended Data Figure 6. Euchromatic H3K4me3Q5ser distribution in DRN.

a, Immunofluorescence images (scale bars equal 100 μm) of H3K4me3Q5ser in brain (DRN) –/+ peptide competition, as indicated. DAPI was used as a nuclear co-stain, and a secondary antibody only control is also included. b, Immunofluorescence images (scale bars equal 10 μm) of H3K4me3Q5ser in DRN (no peptide block) revealing a euchromatic distribution pattern in the nucleus with near total exclusion from DAPI rich chromocenters typical of neurons. c, Immunofluorescence images (scale bars equal 100 μm) of H3K4me3Q5ser in DRN, counter stained with DAPI, NeuN (a neuronal cell marker) and Tph2 (a marker of serotonergic neurons). Merged images reveal that H3K4me3Q5ser is not only expressed in serotonergic neurons (NeuN+/Tph2+, yellow circles), but also in non-serotonergic neurons (NeuN+/Tph2–, white circles) and in non-neuronal cells (NeuN–/Tph2–, red circles). Aq = aqueduct. d, WB validation of Tph2 KO in DRN of Tph1/2 KO mice. DB was used to control for loading. e, Immunofluorescence validation of 5-HT depletion in DRN of Tph1/2 KO mice vs. wildtype littermate controls (scale bars equal 100 μm). For all immunofluorescence experiments (a-e), results were confirmed in ≥ 2 independent experiments. f, WB validation that Tph1/2 KO results in loss of H3K4me3Q5ser signal in DRN (n=11 wildtype vs. n=7 Tph1/2 KO, two-tailed Student’s t-test; t₁₆=3.425, **p=0.0035); no effects on H3K4me3 or total H3 expression were observed. Data presented as average ± SEM.