Fig. 1. Antisense depletion of maternal FoxH1: 4 ng FoxH1 antisense oligo injected into oocytes causes a depletion of FoxH1 mRNA in oocytes that is maintained through early embryogenesis. (A,B) Control and FoxH1-depleted oocytes and embryos derived from the same batch of oocytes were cultured to the stages shown, frozen, and assayed by real-time RT-PCR. Expression levels were normalized to ODC. (A) No wave of zygotic transcription of Foxh1 is seen in control or FoxH1-depleted embryos at the gastrula and neurula stages. (B) The related family member Fast3 is a zygotic transcript, expressed in control and FoxH1-depleted embryos, at the same time as the marker of the mid-blastula transition, GS17. Oocytes and embryos were cultured, frozen, and assayed by real-time RT-PCR. Expression levels were normalized to ornithine decarboxylase (ODC). (C) ARE-luciferase activity is induced in animal caps by activin protein (10 ng/ml), and this induction is severely inhibited in FoxH1-depleted animal caps at the early gastrula stage. (D) ARE-luciferase activity is induced by endogenous nodal signaling in the vegetal (DNA Veg), or equatorial region (DNA EQ) of control embryos at the early gastrula stage. This activation is significantly reduced in FoxH1-depleted explants. (E) FoxH1 antisense oligo causes dose-responsive effects on head and axis formation. Oocytes injected with 2.5 and 3 ng of oligo develop as embryos with a headless phenotype. (F) The morphology of a FoxH1-depleted embryo at the swimming tadpole stage compared to control. (G) In histological sections, headless, FoxH1-depleted embryos at the late tailbud stage embryos have abnormal dorsal axes, lacking notochords and with somites fused across the midline (arrow). (H) Tailbud stage wild-type and FoxH1 embryos showing Xgal labeled progeny of one ventral cell injected at the four-cell stage, at the equator. Although FoxH1 depletion reduces the length of the embryo, the progeny of the ventral cell are in the same posterior and trunk locations as the control.