||Fig. 3. Analysis of xFog expression pattern by RNA in situ hybridization on developmentally staged (albino) embryos. The pattern of xFog expression (A-E) in developing Xenopus embryos is a combination
of the xGata gene expression patterns (F-I). (A) At stage 15, expression starts in the presumptive heart and the presumptive ventral blood island, possibly extending up into the presumptive pronephric region,
but excluded from the presumptive liver. P, posterior. (B) At stage 23, expression is pronounced in heart primordia, similar to xGata-6 (F). (C) At stage 27, expression is high in heart tube, and in the ventral blood island (indicated by stars, very similar to xGata-2, shown in G). Expression is also seen in midbrain and hindbrain, and in the otic vesicle (indicated by white arrow, similar to xGata-3 shown in H).(D) At stage 33, xFog continues to be highly expressed in the heart and ventral blood island. The faint staining in the region around the midline is either the pronephros, similar to xGata-3 (H) or a blood
vessel. Expression is also seen in the eyes and brain (similar to xGata-3 (E,J) At stage 38, expression of xFog is pronounced in heart and surrounding tissue (similar to xGata-4 in I), midbrain and the posterior
region of the ventral blood island. (F) xGata-6, stage 23; (G) xGata-2, stage 28; (H) xGata-3, stage 26; (I) xGata-4, stages 38 (bottom) and 40 (top); (J) xFog, stage 38, cleared embryo. (K,L) Transverse section
of a stage 29 embryo. xFog is expressed in the mesodermal layer of the ventral blood island (original magnification: (K) ´100, (L) ´400; v, ventral; d, dorsal; se, sensorial ectoderm; en, endodermal yolk mass; m, mesodermal layer.