DYNAMIC EXPRESSION OF CHICKEN SOX2 AND SOX3 GENES IN ECTODERM INDUCEDTO FORM NEURAL TISSUE

The chick genes, cSox2 and cSox3, are members of a large family of gen es that encode transcription factors. Previous studies have shown that these genes are predominantly expressed in the central nervous system during embryonic development. We show that cSox3 is expressed through out the ectoderm that is competent to form nervous tissue before neura l induction. The expression of cSox3 is lost from cells as they underg o gastrulation to form nonectodermal tissues; the transcription factor . Brachyury, appears in cells about to undergo gastrulation a short ti me before cSox3 transcripts are lost. Therefore, Brachyury expression may act functionally upstream of cSox3 downregulation, cSox3 expressio n is also lost from non-neuronal ectoderm shortly after the neural pla te becomes morphologically apparent, cSox2 expression increases dramat ically in the central nervous system as neural ectoderm is established . The appearance of cSox2 in neural ectoderm represents one of the ear liest molecular responses to neural induction documented thus far. (C) 1997 Wiley-Liss, Inc.