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Figure 4. Inhibition of Flow Causes Laterality Defects in Xenopus Tadpoles In Vivo(A) Experimental set-up. Control buffer or methylcellulose (MC) dissolved in buffer was injected with a hypodermic needle into the archenteron close to the GRP (indicated in light green) of neurula-stage embryos. Embryos were cultured to stages 22–34 for marker-gene analysis by whole-mount in situ hybridization or to stage 45 for assessment of organ situs.(B and C) Expression patterns of nodal (B) and Pitx2 (C) in buffer- (co) and MC-injected (MC) specimens.(D) Situs solitus (ss) in control-injected (left) and situs inversion (si) and heterotaxia (ht) in MC-injected tadpoles. Gut coiling (indicated by red dashed arrows) and positioning of the gall bladder (white arrows) are shown by autofluorescence in the top row; the direction of heart looping is highlighted by red asterisks outlining ventricle and outflow tract in the bottom row. Only embryos with a dorsal-anterior index of 5 were scored.(E) Summary of laterality defects in 12 MC-injection experiments with 331 control- and 458 MC-injected embryos (cf. Tables S1 and S2).Abbreviations are as follows: a, anterior; bp, blastopore; d, dorsal; l, left; p, posterior; r, right; and v, ventral. |
