Vol44 No.11: 939-947

Maternal Mga is required for Wnt signaling and organizer formation in the early Xenopus embryo

Fei Gu^†, Huijuan Shi^†, Li Gao, Haiyan Zhang, and Qinghua Tao^*

(School of Life Sciences, Tsinghua University, Beijing 100084, China)

Abstract
����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/��-catenin during organizer induction. The depletion of maternal XTcf3 resulted in the ectopic expression of Xnr3 and Siamois, suggesting the activity of ��-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 ��-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 ��-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 ��-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.

Received: 2012-6-4����Accepted: 2012-8-14

†These authors contributed equally to this work.

*Corresponding author . Tel: +86-10-62788745; Fax: +86-10-62792749; E-mail: [email protected]

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