V. Knezevic et al., THE ORGANIZER-ASSOCIATED CHICK HOMEOBOX GENE, GNOT1, IS EXPRESSED BEFORE GASTRULATION AND REGULATED SYNERGISTICALLY BY ACTIVIN AND RETINOICACID, Developmental biology, 171(2), 1995, pp. 458-470
Gnot1, a Not (for notochord) family homeobox gene, is expressed in the
chick pregastrulation blastoderm. Gnot1 expression in the epiblast is
upregulated as the posteriorly derived hypoblast moves forward anteri
orly to form a layer beneath it, which is of particular interest consi
dering the known inductive role of the hypoblast in axis formation in
the chick. Both activin and retinoic acid are able to activate Gnot1 e
xpression in cultured blastodermal cells and show a strong synergistic
effect when applied in combination. Strong superinduction of Gnot1 tr
anscripts in the presence of cycloheximide also indicates the presence
of a potent and labile intracellular inhibitor capable of modulating
Gnot1 expression. During gastrulation, Gnot1 transcripts become locali
zed specifically to tissues associated with ''organizer'' function (He
nsen's node, head process, notochord). The expression data and the res
ponse to mesoderm inducing factors and axial ''caudalizing'' signals s
uggest that Gnot1 may be involved in specification of the embryonic bo
dy axis and could play a part in regulating features of the trunk/tail
organizer in the chick embryo. (C) 1995 Academic Press, Inc.