(A–D) Coronal sections of adult SVZ treated for immunohistochemistry, TRα1 (red in A and B) is not expressed in OLIG2+ (grey) oligodendrocyte progenitors (A), nor SOX10+ (green) oligodendrocyte progenitors (B), but is expressed in DCX+(green) neuroblasts (A) in the adult mouse SVZ. EGFR (red) is expressed in OLIG2+ (green) oligodendrocyte progenitors (C) but not in DCX+ (red) neuroblasts (middle panel in C). OLIG2 (red) and SOX10 (green) are co-expressed in oligodendrocyte progenitors (right panel in C), but very few OLIG2+ cells express DCX (white arrowhead in A). (D) Schematic representation of the brain area investigated. Tagged TRα1 was detected in TRα+/° mutant mice using a β-Gal antibody (A). To examine TRα1 expression in WT mice (B) a TRα1 antibody verified on TRα+/° mutant mice (see materials and methods) was used. Scale bar: 10 µm. (E) T3 represses Egfr transcription in the adult SVZ. (means ± SEM, three experiments are pooled, n = 12 mice, **p=0.001, t = 3.64, df = 30; unpaired two-tailed Student’s t test) (F) In vivo, T3 repression of Egfr-luc requires an intact TRE. Transcription from wild-type (WT) and mutated (mut) constructs was compared following saline (NaCl) or T3 injection. (means ± SEM, three experiments were pooled, n = 21–24 mice per group, **p<0.01. Kruskal-Wallis test followed by a Dunn’s post-hoc test) (G) Transcription from pEgfr-Luc following loss (sh-TRα1 versus sh-ctl; means ± SEM, n = 16 mice, *p=0.039, t = 2.16, df = 27; Unpaired two-tailed Student’s t test) and gain (TRα1 over-expression versus control plasmid PSG5; means ± SEM, n = 12 mice, **p=0.043, t = 3.40, df = 14; Unpaired two-tailed Student’s t test with Welch’s correction) of TRα1 function.