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Acta Biochim Biophys Sin (Shanghai) November 1, 2012; 44 (11): 939-47.
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Maternal Mga is required for Wnt signaling and organizer formation in the early Xenopus embryo.

Gu F , Shi H , Gao L , Zhang H , Tao Q .

Maternal Wnt11 is both necessary and sufficient for the formation of Spemann organizer in Xenopus embryo. Xnr3 and Siamois have been identified as the direct target genes of maternal Wnt11/β-catenin during organizer induction. The depletion of maternal XTcf3 resulted in the ectopic expression of Xnr3 and Siamois, suggesting the activity of β-catenin/XTcf3 is strictly regulated in the early Xenopus embryos. Here, we show that Xenopus mga (Xmga) is a maternal gene required for dorsal axis formation. Overexpression experiments indicate that mouse Mga potentiates the activity of β-catenin in the induction of organizer-specific genes. Depletion of maternal Xmga results in the dramatic decrease of the expression of organizer genes and ventralization phenotype, indicating that Xmga is required for β-catenin function and organizer formation. Depletion of XTcf3 cannot rescue organizer gene expression and axis formation in Xmga-depleted embryos, suggesting Xmga is downstream of XTcf3 during organizer induction. We conclude that maternal Xmga is critical for the function of β-catenin during organizer formation and dorsal development of Xenopus embryo. To our knowledge, this is a report for the first time to implicate Mga in regulating Wnt signaling.

PubMed ID: 23070227
Article link: Acta Biochim Biophys Sin (Shanghai)

Species referenced: Xenopus
Genes referenced: ctnnb1 mga nodal3.1 nodal3.2 sia1 tcf3 tcf7l1 wnt11