Sox2 gene regulation via the D1 enhancer in embryonic neural tube and neural crest by the combined action of SOX2 and ZIC2

• Published in: Genes to cells : devoted to molecular & cellular mechanisms 2020-04, Vol.25 (4), p.242-256
• Main Authors: Iida, Hideaki, Furukawa, Yoko, Teramoto, Machiko, Suzuki, Hitomi, Takemoto, Tatsuya, Uchikawa, Masanori, Kondoh, Hisato
• Format: Article
• Language: English
• Subjects: Binding sites; chicken embryo; ChIP‐qPCR; Chromatin; Electroporation; Embryos; Enhancers; Gene regulation; Genomes; Immunoprecipitation; Neural crest; Neural stem cells; Neural tube; Nucleotide sequence; SOX2; Sox2 D1 enhancer; Sox2 protein; Stem cell transplantation; ZIC2
• ISSN: 1356-9597; 1365-2443
• DOI: 10.1111/gtc.12753

The transcription factor (TF) SOX2 regulates various stem cells and tissue progenitors via functional interactions with cell type‐specific partner TFs that co‐bind to enhancer sequences. Neural progenitors are the major embryonic tissues where SOX2 assumes central regulatory roles. In order to characterize the partner TFs of SOX2 in neural progenitors, we investigated the regulation of the D1 enhancer of the Sox2 gene, which is activated in the embryonic neural tube (NT) and neural crest (NC), using chicken embryo electroporation. We identified essential TF binding sites for a SOX, and two ZIC TFs in the activation of the D1 enhancer. By comparison of dorso‐ventral and antero‐posterior patterns of D1 enhancer activation, and the effect of mutations on the enhancer activation patterns with TF expression patterns, we determined SOX2 and ZIC2 as the major D1 enhancer‐activating TFs. Binding of these TFs to the D1 enhancer sequence was confirmed by chromatin immunoprecipitation analysis. The combination of SOX2 and ZIC2 TFs activated the enhancer in both the NT and NC. These results indicate that SOX2 and ZIC2, which have been known to play major regulatory roles in neural progenitors, do functionally cooperate. In addition, the recently demonstrated SOX2 expression during the NC development is accounted for at least partly by the D1 enhancer activity. Deletion of the D1 enhancer sequence from the mouse genome, however, did not affect the mouse development, indicating functional redundancies of other enhancers. The D1 enhancer of the Sox2 gene is unique for its activity widely covering the embryonic neural tube and neural crest. This enhancer was found to be activated by cobinding of SOX2 and ZIC2, the transcription factors which have been known to be the major regulator of the neural primordia. The D1 enhancer activity accounts for, at least partly, the recently demonstrated SOX2 expression in the neural crest.