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. 2019 Nov 21;39(1):e100882. doi: 10.15252/embj.2018100882

Figure 2. Serotonin signaling during development of the endocrine pancreas in mouse.

Figure 2

  • A–J
    All markers are shown at birth (P0) and at 6 weeks of age: (A‐B1) tryptophan hydroxylase 2 (TPH2), (C‐D2) serotonin (5‐HT), (E‐F1) serotonin reuptake transporter (SERT), (G‐H1) 5‐HT receptor 1F subtype (5‐HT1F), and (I‐J1) 5‐HT1A. Note that all histochemical marks localized to β cells with only sporadic expression, if any, in α cells. 5‐HT was mostly absent in E14.5 pancreata therefore earlier developmental stages are not shown. “Airyscan” (A1) identifies the lack of false‐positive co‐localization between TPH2 and insulin at superresolution. Open arrowheads indicate the lack of co‐localization between select markers. Solid arrows pinpoint cellular sites of co‐existence for pairs of histochemical marks. Asterisks label the positions of nuclei (A1). Representative images are shown from n ≥ 3 pancreata/age group. Hoechst 33342 was used as a nuclear counterstain (pseudo‐colored in gray). Scale bars = 80 μm (D), 20 μm (A–B1,F–J1), 10 μm (C–E1), and 1 μm (A1).
  • K
    Representative Ca2+ signals upon exposure of INS‐1E cells pre‐loaded with Fura2‐AM to 5‐HT at the concentrations indicated. Drugs were superfused acutely as shown. Acetylcholine (ACh, 5 μM) served as positive control. (K1) Quantitative analysis of Ca2+ responses in INS‐1E cells to incrementing concentrations of 5‐HT. Data on the frequency (upper) and amplitude (lower) of Ca2+ transients are shown (normalized to baseline).
  • M
    Tritiated monoamine uptake in INS‐1E cells and its sensitivity to selective SERT and DAT/NET inhibitors.
  • N
    5‐HT uptake in INS‐1E cells in the presence of increasing extracellular glucose concentrations. Reserpine was used to inhibit VMAT2.
  • O
    Schema outlining intracellular signaling and metabolic cascades in fetal β cells for the use of 5‐HT taken up through SERT engagement. “Classical” refers to a neuron‐like/adult‐like scenario with 5‐HT directly loaded into release vesicles by VMAT2 (or a hypothetical alternative transport mechanism).
Data information: Data in (K1–M) were expressed as means ± SEM. Red symbols in K1 mark individual observations, that is, biological replicates. ***P < 0.001, **P < 0.01 (pair‐wise comparisons after one‐way ANOVA).