DeMarais AA and Moon RT (1992), The armadillo homologs beta-catenin and plakogl...

XB-ART-23323

Dev Biol 1992 Oct 01;1532:337-46. doi: 10.1016/0012-1606(92)90118-z.

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The armadillo homologs beta-catenin and plakoglobin are differentially expressed during early development of Xenopus laevis.

DeMarais AA , Moon RT .

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Plakoglobin and beta-catenin are cytoplasmic proteins associated with the intracellular plaques of cell adhesive junctions. While plakoglobin is present in both adherens junctions and desmosomes, beta-catenin is associated with the cadherins that accumulate only in adherens junctions. Both beta-catenin and plakoglobin are homologs of armadillo, a Drosophila segment polarity gene that is considered to be in the wingless signaling pathway. We have characterized the expression and distribution of both plakoglobin and beta-catenin in Xenopus embryos. As shown by RNA blot analysis, beta-catenin and plakoglobin transcripts are present in fertilized eggs and in embryos through to tadpole stage. Whole-mount in situ hybridization indicates that both genes are expressed in the dorsal ectoderm and mesoderm of tailbud- and tadpole-stage embryos and that beta-catenin is expressed in the midbrain. Both plakoglobin and beta-catenin polypeptides are present during early Xenopus development; however, differences exist in the timing of maximal expression. Plakoglobin is present in the fertilized egg, increases in abundance by neurula stage, then declines at the tailbud and tadpole stages. beta-Catenin, recognized by an anti-arm antibody, is also present in the fertilized egg and in blastula-stage embryos. However, beta-catenin continues to be detected at the neurula, tailbud, and tadpole stages when levels of plakoglobin decline. The presence of multiple homologs of armadillo in Xenopus embryos and the differences in their patterns of expression suggest distinct roles for these proteins in processes affected by cell adhesion.

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Species referenced: Xenopus laevis
Genes referenced: ctnnb1 jup

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	FIG. 1. Comparison of the predicted partial amino acid sequence of Xenows plakoglobin, X-plak, and the sequence of the corresponding region of Xenopus fi-catenin, X-P-cat (McCrea et aZ., 1991), with the sequence of human plakoglobin, h-plak (Franke et aZ.,1 989)D. ashesre present amino acids that are identical to those of human p_la koglo-b in. The numbers in parentheses denote the positions of the amino acids in the published sequences of human plakoglobin and Xenopus B-catenin.


	FIG. 4. Temporal and spatial expression of @-eatenin and plakoglobin polypeptides during Xenopus development. Western blots of total protein extracted from whole embryos (A, B; 2 embryo equivalents/lane) or dissected tailbud embryo pieces (C; 10 pieces/lane) were probed with primary antibodies directed against either urmadillo (A; o-cat) or human plakoglobin (B; plak). All blots were reprobed with an a-fodrin (a-fod) antibody for comparison to an unrelated structural protein. (A) Temporal expression of fl-catcnin. Lane 1: fertilized egg (FE), lane 2: blastula (B), lane 3: gastrula (G), lane 4: neurula (N), lane 5: early tailbud (ETB), lane 6: late tailbud (LTB), lane ‘7: tadpole (T), lane 8: fertilized egg (FE), long exposure; lane 9: blastula (B), long exposure. (B) Temporal expression of plakoglobin. Lane 1: fertilized egg (FE), lane 2: blastula (B), lane 3: gastrula (G), lane 4: neurula (N), lane 5: tailbud (TB), lane 6: tadpole (T). (C) Spatial distribution of B-catenin and plakoglobin polypeptides in the early tailbud (stage 24) embryo. Embryos were dissected as in Fig. 2B and pooled total protein from each approximately equal-sized region was analyzed by Western blot. Lane 1: protein from tailbud heads (H), lane 2: protein from middorsal regions (MD), lane 3: protein from midventral regions (MV), lane 4: protein from tailbud tails (T)
	jup (junction plakoglobin) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 33-34, lateral view, anterior left, dorsal up.