XB-ART-48036Sci Rep January 1, 2013; 3 2278.
Single blastomere expression profiling of Xenopus laevis embryos of 8 to 32-cells reveals developmental asymmetry.
We have measured the expression of 41 maternal mRNAs in individual blastomeres collected from the 8 to 32-cell Xenopus laevis embryos to determine when and how asymmetry in the body plan is introduced. We demonstrate that the asymmetry along the animal-vegetal axis in the oocyte is transferred to the daughter cells during early cell divisions. All studied mRNAs are distributed evenly among the set of animal as well as vegetal blastomeres. We find no asymmetry in mRNA levels that might be ascribed to the dorso-ventral specification or the left-right axis formation. We hypothesize that while the animal-vegetal asymmetry is a consequence of mRNA gradients, the dorso-ventral and left-right axes specifications are induced by asymmetric distribution of other biomolecules, probably proteins.
PubMed ID: 23880666
PMC ID: PMC3721081
Article link: Sci Rep
Species referenced: Xenopus laevis
Genes referenced: acta1 axin1 bmp2 ccni cdx1 cdx2 ctnnb1 cyc1 dazl ddx25 dvl2 dvl3 eef1a1 foxh1.2 foxr1 fzd7 gdf1 gsk3b lrp6 maml1 mapk8 mark3 mos odc1 otx1 pax6 pias1 pou5f3.3 stat3.1 stat3.2 tcf7l1 trim36 tubb vegt wnt11 zp3
Article Images: [+] show captions
|Figure 1. PCA of profiled blastomeres collected from early developmental stages of Xenopus laevis.Triangles indicate blastomeres from the 8-cell stage; squares from the 16-cell stage, and circles from the 32-cell stage. Blastomeres originating from the animal hemisphere are shown in red and those from the vegetal hemisphere are shown in blue. Left and right graphs are data from two different females (left: four embryos from 8-cell stage, four embryos from 16-cell stage, and one 32-cell stage embryo, in total 128 blastomeres; right: two embryos from 8-cell stage, three from 16-cell stage, and one from 32-cell stage, in total 96 blastomeres).|
|Figure 2. Hierarchical clustering of blastomeres and mRNAs of Xenopus laevis early embryos presented as heatmaps.One embryo from each developmental stage was arbitrarily chosen for the cluster analysis. (A) 8-cell, (B) 16-cell and (C) 32-cell embryo. Green color indicates low expression and red high expression. The dendrograms clustering blastomeres and genes are shown in the top and left side of the heatmap, respectively. In the dendrograms similarity between blastomeres/genes is indicated by the height at which they are joined.|
|Figure 3. Principal component analysis of maternal genes.(A) 8-cell stage (four embryos/32 cells analyzed), (B) 16-cell stage (four embryos/64 cells analyzed), and (C) 32-cell stage (32 cells analyzed) embryos. Three clusters are seen in all the developmental stages. First cluster comprises 18S rRNA, 5S rRNA, and cyc1(mitochondrial cytochrome c); second cluster vg1, cdx1 (xcad2), wnt11, dazl, vegt, ddx25 (deadsouth), otx1, and trim36; third cluster (red squares) fzd7, par1, bmp2, pias1, dvl2, dvl3, lrp6, foxr1, fart1, mapk8, odc1, axin1, est1, U3 snoRNA, apc, gapdh, acta, eef1a1, tcf3, zpc, RNA polymerase II, gsk3b, maml1, tubb, ctnnb1 (β-catenin), mos, oct60, foxh1, stat3, and pax6. The animal-vegetal distinction is found along the y-axis (PC2), while differences in expression level of the maternal transcripts is reflected along the x-axis (PC1).|
References [+] :
Aanstad, Predictability of dorso-ventral asymmetry in the cleavage stage zebrafish embryo: an analysis using lithium sensitivity as a dorso-ventral marker. 2000, Pubmed