XB-ART-1734Dev Dyn August 1, 2005; 233 (4): 1546-53.
Organization and developmental expression of an amphibian vascular smooth muscle alpha-actin gene.
A gene encoding a putative homologue of the avian and mammalian vascular smooth muscle alpha-actin was isolated from an amphibian, Rana catesbeiana, and characterized in terms of its sequence, organization, and expression pattern. To assess the expression of this gene during amphibian embryonic development, a cDNA encoding the Xenopus homologue of this mRNA was isolated and characterized by in situ hybridization. The expression of this gene was not detected in the enteric smooth muscle cells or, unlike its avian and mammalian homologues, in the somites/skeletal muscle of the Xenopus embryos/tadpoles. Its initial expression coincides with the onset of cardiac muscle differentiation and is coincidental with the expression of the cardiac alpha-actin mRNAs in the heart-forming region of the stage 26/27 embryo. As development proceeds, transcripts from this gene are expressed throughout the developing heart until the formation of the heart chambers is completed and, thereafter, its expression becomes restricted to the outflow tract of the tadpole heart. The subsequent restricted expression of this gene to the vascular system in both of these amphibians identifies it as the amphibian homologue of the avian and mammalian vascular smooth muscle alpha-actin.
PubMed ID: 15965984
Article link: Dev Dyn
Species referenced: Xenopus
Genes referenced: acta2 actl6a
Article Images: [+] show captions
|Figure 6. Expression of Xsm alpha -actin in developing Xenopus laevis embryos. A-D: Lateral and ventral views of late tail bud embryos (stage 26/27) after whole mount in situ hybridization to detect smooth muscle alpha -actin (Xsm alpha -actin; A,B) and cardiac alpha -actin (Xc alpha -actin1; C,D) gene expression. Although transcripts from both genes are colocalized in the bilateral domains of the heart-forming (h) region in these embryos, Xsm alpha -actin mRNA, unlike Xc alpha -actin1 mRNA, is not present in the somites (s). E: A lateral view of a stage 31 Xenopus embryo showing that Xsm alpha -actin expression is throughout the developing heart tube. F,G: Lateral views of the anterior portion of Xenopus embryos at stages 34 (F) and 41 (G) showing that Xsm alpha -actin transcripts are throughout the heart, up to and including the onset of chamber formation. H: In situ hybridization of a cross-section through the heart of a stage 59 tadpole showing that after the heart chambers [atria (a) and ventricle (v)] are formed Xsm alpha -actin transcripts are confined to the outflow tract (oft) of the heart. I: A higher magnification image of the outflow tract seen in H.|