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Figure 6. Embryonic expression of Xqua mRNA. Whole-mount in situ hybridization using an RNA probe specific to the 5-kb embryonic form of Xqua. (A) Lateral view of a stage 11 gastrula embryo shows that transcripts are first detected in the chordamesoderm of the dorsal blastopore lip. (B) By late gastrula, Xqua is strongly expressed in the notochord with weak expression in the circumblastoporal region (B, embryo on the right, dorsal view). Embryos hybridized with sense strand control probes (B, embryo on the left) show no staining. In neurula embryos (stage 18) (C, dorsal view;D, posterior view; E, anterior view), the expression domain has expanded to include the notochord, paraxial mesoderm, circumblastoporal region, and the neural plate. In tailbud embryos (stages 24–30) (F,G), Xqua is strongly expressed in the brain and neural tube, the developing heart, tail blastema, and branchial arches. (G) By late tailbud (stage 30), the expression in the notochord and somites is declining. (H) Cross sections through the head of the stage 30 whole-mount embryo show that expression in the brain is largely restricted to the ventricular and marginal zones and the floor plate. (I) Later in development at hatched tadpole stage, Xqua expression is almost exclusively in the head and heart. (anp) Anterior neural plate; (bp) blastopore; (dl) dorsal lip; (h) heart; (n) notochord. |
