1. Stowers Institute for Medical Research, 1000E 50th Street, Kansas City, Missouri 64110, USA

Correspondence to: Olivier Pourquié¹ Correspondence and requests for materials should be addressed to O.P. (Email: olp@stowers-institute.org).

Abstract

A striking feature of the body plan of a majority of animals is bilateral symmetry. Almost nothing is known about the mechanisms controlling the symmetrical arrangement of the left and right body sides during development. Here we report that blocking the production of retinoic acid (RA) in chicken embryos leads to a desynchronization of somite formation between the two embryonic sides, demonstrated by a shortened left segmented region. This defect is linked to a loss of coordination of the segmentation clock oscillations¹. The lateralization of this defect led us to investigate the relation between somitogenesis and the left–right asymmetry machinery^{2, 3} in RA-deficient embryos. Reversal of the situs in chick^{4, 5} or mouse⁶ embryos lacking RA results in a reversal of the somitogenesis laterality defect. Our data indicate that RA is important in buffering the lateralizing influence of the left–right machinery, thus permitting synchronization of the development of the two embryonic sides.

1. Stowers Institute for Medical Research, 1000E 50th Street, Kansas City, Missouri 64110, USA

Correspondence to: Olivier Pourquié¹ Correspondence and requests for materials should be addressed to O.P. (Email: olp@stowers-institute.org).

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