July 15, 2009;
Unexpected functional redundancy between Twist and Slug (Snail2) and their feedback regulation of NF-kappaB via Nodal and Cerberus.
network controls axis and mesoderm
formation in Drosophila. Using translation-blocking morpholinos and hormone-regulated proteins, we demonstrate the presence of an analogous network in the early Xenopus embryo
. Loss of twist
) function leads to a reduction of mesoderm
and neural crest
markers, an increase in apoptosis, and a decrease in snail1
) and snail2
) mRNA levels. Injection of snail2
mRNA rescues twist''s loss of function phenotypes and visa versa. In the early embryo NF-kappaB
, and snail1
mRNA levels; similarly Nodal
, and relA
RNA levels. Both Twist
negatively regulate levels of cerberus
RNA, which encodes a Nodal
morphogenic protein (BMP), and Wnt inhibitor. Cerberus''s anti-Nodal
activity inhibits NF-kappaB
activity and decreases relA
RNA levels. These results reveal both conserved and unexpected regulatory interactions at the core of a vertebrate''s mesodermal specification network.
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References [+] :
Fig. 3. Compared to uninjected embryos (A, C, E, G), injection of the Twist morpholino (7 ng/embryo) (B, D, F, H) into one-cell of two-cell embryos led to the loss of xbra (A, C), antipodean/vegT (B, D), and chordin (E, F) expression (arrows), and the expansion (arrow) of the expression domain of the endodermal marker endodermin (G, H). “yp” marks the yolk plug of gastrula stage embryos, “BP” marks the blastopore — all embryos are oriented similarly, with the dorsal lip oriented to the lower right.
Fig. 5. Compared to uninjected embryos (A and top embryo in part H), the unilateral injection of either Snail2 (B) or Twist (C) morpholinos (7 ng/embryo) in two-cell embryos led to the anterior loss of myoD RNA in situ hybridization staining in stage 22/24 embryos. The loss of myoD staining in Twist (D) or Snail2 (E) morphant embryos was rescued by Twist RNA injection (500 pg/embryo); similarly the loss of myoD staining in Snail2 (F) or Twist (G) morphant embryos was rescued by the injection of Snail2-GFP RNA (500 pg/embryo). All embryos are oriented with anterior to the left and dorsal to the top. (H) In larvae derived from unilaterally injected 2-cell embryos there was a pronounced curvature toward the injected side. In all cases, it is worth noting that these embryos survived gastrulation and are therefore likely to represent partial, rather than complete, loss of function phenotypes.
Agius, Endodermal Nodal-related signals and mesoderm induction in Xenopus. 2000, Pubmed