Fig 1. tbx2 expression in the blastula and gastrula stage ectoderm is dependent on Xema/Foxi1e activity.

(A) Xema morpholino-mediated knockdown (Xema MO) inhibits expression of tbx2. RT-PCR analysis of early gastrula stage explants. Ornithine decarboxylase (ODC) was used as a loading control (Bassez et al., 1990). (B) Whole-mount in situ hybridization of early gastrula stage embryos (stage 10.5). Tbx2 expression is seen as a blue stain throughout the animal pole of albino embryos; tbx2 expression is excluded from the vegetal pole. Expression of the panmesodermal marker Xbra is only detected in the marginal zone of gastrula stage embryos, as expected (Smith et al., 1991). (C) RT-PCR analysis of tbx2 in late blastula stage explants. tbx2 is expressed in the animal cap and excluded from vegetal pole explants; vegt is only expressed in vegetal explants, as expected (Lustig et al., 1996; Stennard et al., 1996; Zhang and King, 1996; Horb and Thomsen, 1997). (D) Inner and outer layers of early gastrula stage ectoderm was separated and analyzed by RT-PCR for expression of tbx2. tbx2 is expressed in the inner layer of the ectoderm; Delta is only expressed in the inner layer and serves as a control and epidermal keratin is only expressed in the outer layer (Jonas et al., 1985; Chalmers et al., 2002). All experiments shown or described in this figure, and throughout the manuscript, were performed at least three times.