Getting Your Left Right

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Science  18 Oct 2002:
Vol. 298, Issue 5593, pp. 497
DOI: 10.1126/science.298.5593.497b

Left-right asymmetry—whereby, for example, the heart is on the left side of the body with functionally distinct left and right chambers—is established very early in development. In the African toad Xenopus, and in chick embryos, Levin et al. now show that the H+ and K+ ATPase transporter is required in the formation of embryos with a normal left-right body axis. In fertilized Xenopus eggs, maternal transporter messenger RNA is symmetrically expressed; however, during the first two cell divisions of development it becomes localized. In chick embryos the transporter mRNAs are again symmetrically localized, but a difference in membrane potential is generated either side of the primitive streak. In both systems, interfering with transporter activity caused randomization of the expression pattern of asymmetrically expressed genes, resulting in opposite handedness in the organs and tissues produced later in development—including the heart, the gut, and the gall bladder. Thus, very early in development, differential ion fluxes generated by the H+/K+ ATPase are key to determining future left-right asymmetry. — SMH

Cell111, 77 (2002).

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