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Development September 1, 2009; 136 (18): 3057-65.

Vegetally localized Xenopus trim36 regulates cortical rotation and dorsal axis formation.

Specification of the dorsoventral axis in Xenopus depends on rearrangements of the egg vegetal cortex following fertilization, concomitant with activation of Wnt/beta-catenin signaling. How these processes are tied together is not clear, but RNAs localized to the vegetal cortex during oogenesis are known to be essential. Despite their importance, few vegetally localized RNAs have been examined in detail. In this study, we describe the identification of a novel localized mRNA, trim36, and characterize its function through maternal loss-of-function experiments. We find that trim36 is expressed in the germ plasm and encodes a ubiquitin ligase of the Tripartite motif-containing (Trim) family. Depletion of maternal trim36 using antisense oligonucleotides results in ventralized embryos and reduced organizer gene expression. We show that injection of wnt11 mRNA rescues this effect, suggesting that Trim36 functions upstream of Wnt/beta-catenin activation. We further find that vegetal microtubule polymerization and cortical rotation are disrupted in trim36-depleted embryos, in a manner dependent on Trim36 ubiquitin ligase activity. Additionally, these embryos can be rescued by tipping the eggs 90 degrees relative to the animal-vegetal axis. Taken together, our results suggest a role for Trim36 in controlling the stability of proteins regulating microtubule polymerization during cortical rotation, and subsequently axis formation.

PubMed ID: 19675128
PMC ID: PMC2730363
Article link: Development
Grant support: [+]

Species referenced: Xenopus
Genes referenced: eomes gsc krt61 myod1 nodal3.1 odc1 sia1 trim36 wnt11
Antibodies: Ctnnb1 Ab7 Krt5.2 Ab1 Tuba4b Ab2
Morpholinos: trim36 MO1

Article Images: [+] show captions
References [+] :
Belenkaya, pygopus Encodes a nuclear protein essential for wingless/Wnt signaling. 2002, Pubmed, Xenbase