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Fig. 1. Left versus right stomach transcriptome analyses identify sim2. (A) Left lateral views of Lepidobatrachus laevis embryos at stages before (GS18), during (GS19-GS20) and after (GS21) overt stomach curvature; the stomach region is indicated by the white dashed box. Color-coding of transverse sections indicates the left (L; blue) and right (R; yellow) stomach tissues dissected for transcriptome analyses at each phase of curvature. (B) Heat map of 278 L. laevis transcripts with significant left (blue; 179) or right (yellow; 99) enrichment at each stage of curvature (q-value≤0.01). (C) Venn diagram showing the number of transcripts with left- or right-enrichment at each stage (q-value≤0.01), as well as those asymmetrically expressed at more than one stage. Although no transcripts are consistently right-sided across all four stages, two transcripts are left-sided throughout stomach curvature: pitx2 and sim2. (D) Left (blue) and right (yellow) expression of L. laevis pitx2 and sim2 at each stage of stomach curvature. FPKM, fragments per kilobase of transcript per million mapped reads. Significant differences between sides and stages are indicated by lower case letters, used to label means such that bars bearing different letters are statistically different from one another (P<0.05). (E) Diagrams of Xenopus embryos (left lateral and transverse views) at equivalent phases (NF35, NF37, NF39, NF40) of stomach curvature illustrate the approximate planes of section (red dotted lines), and the position of the left (blue) and right (yellow) stomach walls shown in the corresponding tissue sections in F and G. (F,G) The spatial expression patterns of pitx2 (F) and sim2 (G) were validated by RNA ISH. Images in G are neighboring sections from the same embryo shown in F; asterisks demarcate expression in the stomach dorsal midline. See Fig. S1 for additional sim2 expression patterns. Scale bar: 1 mm (A); 500 μm (F,G). |
