IDENTIFICATION OF TGF-BETA-RELATED GENES IN THE EARLY CHICK-EMBRYO

Transforming growth factor-beta (TGF-beta)-related genes have been postulated as possible mesoderm inducers in lower vertebrates. Activin, a member of the TGF-beta family has been recently suggested to be directly involved in the induction of axial mesoderm in frogs and birds. Nodal, a novel TGF-beta-like gene, seems to be essential for mesoderm formation in mice. In this work we have tried to characterize which growth factors of the TGF-beta family are involved in the initial stages of differentiation of the chick embryo. Using degenerate primers to specific regions of the TGF-beta super family in polymerase chain reactions (PCR), we have identified both TGF-beta(2) and TGF-beta(3) transcripts in early stages of chick development. In addition, we have identified a new gene which is transcribed during early chick development. We have called this gene Vgc1 since it is probably the chick homologue of the mouse Vg-related gene Vgr1. RNA coding for the Vgc1 gene was detected by RNAse protection in early stage X blastoderms, gastrula and 3-day-old embryos. In situ hybridization experiments further indicate that Vgc1 RNA is distributed uniformly throughout the various regions of the chick gastrula. The role of Vgc1 in early chick development remains to be established.