Left-right asymmetry in BMP4 signalling pathway during chick gastrulation

Determination of the left-right (L-R) axis was shown recently to implicate several genes, among which TGFP-related molecules such as Activin betaB, le fty1 and 2 and Nodal. We show here that Bmp4 and its signal transduction pa thway partners BMPR IA and Smad1 are transiently expressed on the right sid e of Hensen's node, when L-R polarity is being established. Moreover, Smad1 is expressed asymmetrically in the nascent notochord. These observations s uggest a role for a BMP4-dependent autocrine or paracrine mechanism during early LR determination. (C) 2000 Elsevier Science Ireland Ltd. All rights r eserved.