Tnf levels correlate with immune system-induced regenerative neurogenesis All photomicrographs are lateral views at 48 hpl (except A); asterisk indicates injury site; boxed areas are shown in higher magnification on the right. All qRT-PCR results are relative to unlesioned control, set to 1 and indicated by dashed red line; each dot represents one experiment. (A) Macrophages (mpeg1:GFP+) and Tnf protein are concentrated in the spinal injury site and close to (within 20 μm) motor neuron progenitor cells (olig2:DsRed+). A 4-dpf-larva is shown at 22 hpl (top: merge of all channels; middle: mpeg1:GFP; bottom: Tnf). See Figure S2A for separate channels and S2B for quantification. (B) qRT-PCR shows LPS increases and dexamethasone decreases tnfa expression (Incubation: −6 to 24 hpl for dexamethasone and 0 to 24 hpl for LPS; analysis at 24 hpl; Kruskal-Wallis test p = 0.0007; Dunn’s post-test: ∗p = 0.027; ∗∗∗p = 0.0003; n.s.: p = 0.687. (C) Dexamethasone decreases hdac1 mRNA expression after injury (incubation: −6 to 24 hpl; t test: ∗∗∗∗p = 0.0001). (D) Dexamethasone treatment reduces the number of proliferating motor neuron progenitor ERGs (olig2:GFP+/EdU+; incubation: dexamethasone: −6 to 48 hpl; EdU 0 to 48 hpl; t test: ∗p = 0.040). (E) LPS treatment increases hdac1 mRNA expression after injury (incubation: 0 to 24 hpl; t test: ∗p = 0.023). (F and G) LPS treatment increases the number of proliferating motor neuron progenitor ERGs (olig2:GFP+/EdU+) (F; t test, ∗∗∗∗p < 0.0001) and number of new motor neurons (G; mnx1:GFP+/EdU+; t test, ∗∗∗∗p < 0.0001); incubation: LPS: 0 to 48 hpl; EdU 0 to 48 hpl). Scale bars: 50 μm; 10 μm for insets. Data are represented as mean ± SEM (see also Figure S2; Tables S6–S8).
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