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Wiley Interdiscip Rev Dev Biol May 1, 2012; 1 (3): 371-88.
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Cortical rotation and messenger RNA localization in Xenopus axis formation.

In Xenopus eggs, fertilization initiates a rotational movement of the cortex relative to the cytoplasm, resulting in the transport of critical determinants to the future dorsal side of the embryo. Cortical rotation is mediated by microtubules, resulting in activation of the Wnt/β-catenin signaling pathway and expression of organizer genes on the dorsal side of the blastula. Similar cytoplasmic localizations resulting in β-catenin activation occur in many chordate embryos, suggesting a deeply conserved mechanism for patterning early embryos. This review summarizes the experimental evidence for the molecular basis of this model, focusing on recent maternal loss-of-function studies that shed light on two main unanswered questions: (1) what regulates microtubule assembly during cortical rotation and (2) how is Wnt/β-catenin signaling activated dorsally? In addition, as these processes depend on vegetally localized molecules in the oocyte, the mechanisms of RNA localization and novel roles for localized RNAs in axis formation are discussed. The work reviewed here provides a beginning framework for understanding the coupling of asymmetry in oogenesis with the establishment of asymmetry in the embryo.

PubMed ID: 23801488
Article link: Wiley Interdiscip Rev Dev Biol

Species referenced: Xenopus
Genes referenced: apc arhgef7 axin1 bcl9 ccny chrd.1 ctnnb1 dctn2 dkk1 dvl2 dvl3 ext1 frat1 fzd7 gsk3b kif15 kif4a lrp6 mapk8 nodal nodal1 nog plin2 ppp2r5e prmt2 pygo1 sia1 tcf4 tcf7 tcf7l1 tdgf1.3 tpst1 trim36 tuba8 wnt11b wnt5a

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