CONTROL OF VERTEBRATE LEFT-RIGHT ASYMMETRY BY A SNAIL-RELATED ZINC-FINGER GENE

A gene encoding a zinc finger protein of the Snail family, cSnR, is ex pressed in the right-hand lateral mesoderm during normal chick develop ment. Antisense disruption of cSnR function during the hours immediate ly preceding heart formation randomized the normally reliable directio n of heart looping and subsequent embryo torsion. Implanted ectopic so urces of intercellular signal proteins that are involved in establishi ng normal left-right information randomized the handedness of heart de velopment and also altered the asymmetry of cSnR expression. cSnR thus appears to act downstream of these signals, or perhaps in parallel wi th the latest expressed of them, the Nodal protein, in controlling the anatomical asymmetry.