XB-ART-23782Dev Dyn May 1, 1992; 194 (1): 1-11.
Embryonic expression and functional analysis of a Xenopus activin receptor.
We report the isolation and characterization of a Xenopus activin receptor (XAR1). The amino acid sequence of this protein shows extensive homology with a murine activin receptor. The mRNA is expressed maternally and is ubiquitously distributed during the early stages of embryogenesis. Consistent with a possible role in mesoderm induction and patterning, interference with the normal expression of the receptor by overexpression in the early embryo results in the formation of ectopic dorsal axial structures. During neurulation the XAR1 mRNA is expressed predominantly in the presumptive brain and spinal cord, suggesting an additional function for XAR1 in neurogenesis.
PubMed ID: 1384808
Article link: Dev Dyn
Species referenced: Xenopus
Genes referenced: acvr2b tbx2
Antibodies: Notochord Ab1 Somite Ab1
Article Images: [+] show captions
|Fig. 3. Expression of XARl mRNA during development. A: Developmental poly (A) Northern blot. The XARI transcript is expressed maternally as a 4 kb doublet throughout development. A larger 6 kb zygotic mRNA is detected at stage 11 and persists until stage 20. Arrows indicate size of transcripts. This blot has been probed previously and shown to contain comparable amounts of poly (A) RNA in all lanes (Hemmati- Brivanlou et al., 1991). B: Spatial distribution of XARl RNA at blastula (Stage 8). The EFla control shows that slightly less RNA was loaded in the vegetal vs. animal iane in B. Five embryo equivalents of total RNA are loaded in each lane. A shorter exposure of similar blots reveals a distinct doublet at the 4 kb region, but this is not evident in the darker exposures shown here.|
|Fig. 4. Spatial distribution of the XAR1 transcript during neurogenesis detected by whole mount in-situ hybridization. A: At neurula stage 15 the XARl transcript is detected in neuroectoderm. Arrows delineate the neural plate. 6: Stage 21 neurula. XARl RNA is detected in the brain, eyes, and spinal cord. C: Dorsal view of a stage 23 embryo. Strong expression is detected in the CNS on each side of midline. D: Close-up view of XARl RNA in the anterior CNS. The arrows point to the hindbrain-spinal cord junction. E: Stage 35 tadpole. Most of the transcript is localized in the head of the embryo. F: Close-up view of the head of the same embryo. Arrows point to the rhornbomeres of the hindbrain that show strong expression. Expression can also be seen at the midbrain-hindbrain and midbrain-forebrain junction, anterior wall of the forebrain, the eye (outside of this focal plan), and mandibular arches and pharyngeal pouches. G: Expression of XARl in the spinal cord of the same embryo as shown (E). The RNA is expressed in cells aligned in the ventral side of the spinal cord (arrows). Some cells in the midtrunk region of the dorsal fin are also stained. H: A stage 24 neurula stained with XARl sense probe as a control. All embryos presented are albino. In all cases, the dorsal side is up and anterior is to the right. Panel (F) and (G) were taken under differential interference contrast optics, all other panels were bright light optics. sc = spinal cord, nc = notochord.|
|Fig. 5. Phenotype of embryos overexpressing the XARI mRNA. Panels A and E present a collection of embryos injected in the equatorial region and stained for a notochord (Mab Tor 70) and muscle (Mab 121 101) markers respectively. (A,B,C, and D) are stained with the notochord Mab. (E,F,G, and H) are stained with the muscle Mab. The top of the panels A and E as well as panels B and F are control uninjected embryos. C and D are close up views of two of the embryos shown in A. G and H are close-up views of two of the embryos presented in E. C,D,G, and H show that injection of XARI RNA interferes with the normal development of axial mesoderm by disturbing both notochord and somite development. All embryos presented were lightly pigmented. Dorsal side is up and anterior is to the left for all cases, except B, D, and H, where anterior is to the right.|
|acvr2b (activin A receptor, type IIB) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 35, lateral view, anterior right, dorsal up. Red arrows point to individual rhombomeres R1-R8, and highlight the segmented nature of the hindbrain.|