PITX2 PARTICIPATES IN THE LATE-PHASE OF THE PATHWAY CONTROLLING LEFT-RIGHT ASYMMETRY

Pitx2, a member of the bicoid-related family of homeobox-containing ge nes, is asymmetrically expressed in the left lateral plate mesoderm an d derived tissues during chick and mouse development. Modifications of Pitx2 pattern of expression in the iv mouse mutation correlate with t he situs alterations characteristic of the mutation. Misexpression exp eriments demonstrate that Shh and nodal positively regulate Pitx2 expr ession. Our results are compatible with a Pitx2 function in the late p hase of the gene cascade controlling laterality.