Int J Dev Biol
January 1, 2001;
Making mesoderm--upstream and downstream of Xbra.
of the amphibian embryo
is formed through an inductive interaction in which cells of the vegetal hemisphere
of the embryo
act on overlying equatorial cells. My laboratory is studying the Brachyury
gene, which plays a key role in this interaction, being both necessary and sufficient for normal mesoderm
formation. In this article I describe our attempts to understand how Xenopus Brachyury
) is activated in the right
cells at the right
time, and then to understand how Xbra
exerts its effects.
Int J Dev Biol
[+] show captions
Fig. 1. Identification of Xbra 5’ regulatory sequences.
Expression patterns of the indicated Xbra promoter constructs
at the indicated stages. (A,B) 2.1 kb and 381 base pairs of 5’
Xbra sequence are both sufficient to drive expression of a
reporter gene throughout the involuting mesoderm at stage
11.5, but expression does not occur in the presumptive notochord.
(C,D) Bisected Xenopus embryos at stage 10.5 showing
expression of a reporter gene driven by 2.1 kb of wild-type 5’
Xbra sequence (C) and expression driven by 2.1 kb of 5’
sequence in which the proximal zinc finger target sequence
CAGGTG is mutated to CAGATG (D). Note widespread activation
of the reporter gene in (D).
Fig. 2 Expression patterns of Xbra and Xwnt11. Comparison of the expression patterns
of Xwnt11 (A-C) and Xbra (D-F) at stages 11 (A,D), 12.5 (B,E) and 14 (C,F).