XB-ART-8885Mech Dev June 1, 2001; 104 (1-2): 147-50.
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Xenopus Smad3 is specifically expressed in the chordoneural hinge, notochord and in the endocardium of the developing heart.
The Smads are intracellular signalling molecules that transduce signals from receptors for members of the TGF-beta superfamily to the nucleus. We have cloned the Xenopus orthologue of Smad3 (XSmad3). It is 94.6% identical to human Smad3 at the amino acid level. It is expressed as a maternal mRNA which disappears after stage 10.5, but reappears at the early tailbud stages. It is much less abundant than XSmad2 at the early developmental stages. From Stage 27 onwards XSmad3 is expressed with XSmad2 throughout the head region and in the somitic region. Strikingly however, XSmad3 alone is specifically expressed in the chordoneural hinge, the notochord and in the developing heart. Closer analysis reveals that XSmad3 is specifically expressed in the endocardium but not in the myocardium or pericardium. The chordoneural hinge staining persists at least until stage 40 whereas the staining in the endocardium peaks at approximately stage 32/33.
PubMed ID: 11404094
Article link: Mech Dev
Species referenced: Xenopus
Genes referenced: smad2 smad3
Article Images: [+] show captions
|Fig. 3. Expression of XSmad2 and XSmad3 mRNA detected by in situ hybridization. In situ hybridization using probes specific for XSmad2 (A,C,E,G) or XSmad3 (B,D,F,H–J) on embryos of different developmental stages (indicated at the left). The specific staining is blue. In (A,B), Stage 10.25 embryos were cut in half prior to in situ hybridization analysis, and arrow head indicates the position of the dorsal blastopore lip. In (D,F,H), arrows indicate either the heart staining (Ht) or the chordoneural hinge staining (CNH). Boxed areas in panel (F) are shown magnified in panels (I,J).|
|Fig. 4. Expression of XSmad3 in the heart is restricted to the endocardium. Panels (A–F) represent serial 10 μm transverse sections from anterior to posterior respectively through the heart region of a stage 33 embryo previously stained for XSmad3 by the whole-mount procedure used in the previous panels. e, endocardium; m, myocardium; aa, aortic arch. In panel (C) note that endocardial staining, which is strong in the outflow tract (arrowhead) does not extend into the aortic arches (aa). In panel (E), the section has cut through the endocardium twice as it is a spirally looped tube (both indicated ‘e’): The blue staining is seen specifically in the endocardium.|