CLONING, SEQUENCING, AND EXPRESSIONAL ANALYSIS OF THE CHICK HOMOLOG OF FOLLISTATIN

Follistatin, a secreted glycoprotein, has been shown to act as a poten t neural inducer during early amphibian development. The function of t his protein during embryogenesis in higher vertebrates is unclear, and to further our understanding of its role we have cloned, sequenced, a nd performed an in-depth expressional analysis of the chick homologue of follistatin. in addition we also describe the expression pattern of activin beta A and activin beta B, proteins that have previously been shown to be able to interact with follistatin. In this study we show that the expression of follistatin and the activins do not always over lap. Follistatin was first detected in Hensen's node and subsequently in the region described by Spratt [1952] as the neuralising area. In o lder embryos it was also expressed in a highly dynamic manner in the h indbrain as well as in the somites. We also present evidence that foll istatin may have a later role in the resegmentation of the somites. We were unable to detect the expression of activin beta A during early e mbryogenesis, whereas activin beta B was first expressed in the extend ing primitive streak and subsequently in the neural folds. The results from this study are consistent with a role for follistatin in neural induction but suggest it has additional functions unrelated to its inh ibitory actions on activins. (C) 1995 Wiley-Liss, Inc.