Fig. 3

mych and potentially also mycl1b are directly regulated by Pou5f1.

Pou5f1 overexpression in MZspg mutants by pou5f1-VP16 mRNA injection into one-cell stage embryos (A-F; left embryos in each panel) and non-injected controls (A, C and E; MZspg middle and WT right embryos in each panel; B, D and F; MZspg right embryo in each panel). The embryos in B, D and F are in addition treated with CHX starting at 1.5 hpf. The mych expression can be rescued by Pou5f1-VP16 in both, CHX treated and untreated embryos, and therefore the regulatory influence of Pou5f1 should be direct (A-B). The expression of mycl1b can also be rescued by Pou5f1-VP16 overexpression in CHX untreated MZspg embryos, but is also strongly upregulated in CHX treated MZspg embryos, even without the injection of pou5f1-VP16 mRNA (C-D). Thus the experiment cannot proove whether activation of mycl1b by Pou5f1 is direct or not. We used notail as negative control, because its expression is independent of Pou5f1 function (E), and depends on zygotic gene products.