Tsukushi double action in primitive streak induction Available to Purchase

The induction of the primitive streak, which defines the axes of the embryo, occurs during gastrulation. In chick embryos, its induction and that of Hensen's node (a thickening of the anterior primitive streak that acts as an organizer) requires VG1 (a TGFβ superfamily member) signals, WNT signals and BMP antagonists. On p. 3777, Ohta and co-workers report that Tsukushi (TSK) - originally identified as a BMP antagonist - cooperates with VG1 to promote the formation of the primitive streak and Hensen's node. They show that alternative splicing of TSKmRNA produces TSKA and TSKB; both proteins interact with VG1, but TSKA is the stronger BMP antagonist. TSKA expression is highest in Hensen's node(a source of anti-BMP signals), they report, whereas TSKB accumulates in the middle of the primitive streak (where VG1 is expressed) and is required for the induction of Hensen's node. The researchers conclude that the TSK isoforms...