Figure 3

Isl2a mutants show reduced thyroid function. (A) The assessment of tg expression in isl2a mutants at 3 dpf and 5 dpf via whole-mount in situ hybridization. At 5 dpf, isl2a^-/- zebrafish had lower expression of tg and tshba as denoted by black arrows and arrowhead, respectively. Scale bar = 50 µm. (B) qRT-PCR analysis of the total expression of tg, slc5a5, tpo, tshba, and cga in isl2a^+/+ and isl2a^-/- larvae at 5 dpf. Error bars represent ± SD (n = 5, 15 fish per tube). (C) Both EGFP (green) and EdU immunoreactivity (red) were present in the thyroid of 120 hpf Tg (tg:egfp) wild-type (n = 7) larvae, whereas nearly no EdU-positive cells were detected within the tg domain in isl2a^-/- larvae (n = 6). There were also no TUNEL-positive cells (red) in the tg domain at 127 hpf. Scale bar = 500 µm. (D) Thyroxine (T4) and 3,5,3′-triiodothyronine (T3) levels in the zebrafish body at 44 dpf. Error bars represent ± SD (n = 4). Asterisks indicate significant differences between isl2a^+/+ and isl2a^-/- groups (*P < 0.05, **P < 0.01).