PUBLICATION

Dorsal activity of maternal squint is mediated by a non-coding function of the RNA

Authors

Lim, S., Kumari, P., Gilligan, P., Quach, H.N., Mathavan, S., and Sampath, K.

ID

ZDB-PUB-120702-34

Date

2012

Source

Development (Cambridge, England) 139(16): 2903-2915 (Journal)

Registered Authors

Gilligan, Patrick, Kumari, Pooja, Lim, Shi Min, Mathavan, S., Quach, Helen Ngoc Bao, Sampath, Karuna

Keywords

none

MeSH Terms

beta Catenin/metabolism
Zebrafish Proteins/antagonists & inhibitors
Zebrafish Proteins/genetics*
Zebrafish Proteins/metabolism*
Male
Oligonucleotides, Antisense/genetics
Mutagenesis, Site-Directed
Body Patterning/genetics*
Body Patterning/physiology*
Female
Models, Biological
Nodal Signaling Ligands/antagonists & inhibitors
Nodal Signaling Ligands/genetics*
Nodal Signaling Ligands/metabolism*
Animals, Genetically Modified
Wnt Signaling Pathway
Zebrafish/embryology
Zebrafish/genetics*
Zebrafish/metabolism*
3' Untranslated Regions*
Mutant Proteins/genetics
Mutant Proteins/metabolism
Recombinant Proteins/genetics
Recombinant Proteins/metabolism
Gene Expression Regulation, Developmental
Animals

(all 26)

PubMed

22721777 Full text @ Development

Abstract

Despite extensive study, the earliest steps of vertebrate axis formation are only beginning to be elucidated. We previously showed that asymmetric localization of maternal transcripts of the conserved zebrafish TGFβ factor Squint (Sqt) in 4-cell stage embryos predicts dorsal, preceding nuclear accumulation of β-catenin. Cell ablations and antisense oligonucleotides that deplete Sqt lead to dorsal deficiencies, suggesting that localized maternal sqt functions in dorsal specification. However, based upon analysis of sqt and Nodal signaling mutants, the function and mechanism of maternal sqt was debated. Here, we show that sqt RNA may function independently of Sqt protein in dorsal specification. sqt insertion mutants express localized maternal sqt RNA. Overexpression of mutant/non-coding sqt RNA and, particularly, the sqt 3'UTR, leads to ectopic nuclear β-catenin accumulation and expands dorsal gene expression. Dorsal activity of sqt RNA requires Wnt/β-catenin but not Oep-dependent Nodal signaling. Unexpectedly, sqt ATG morpholinos block both sqt RNA localization and translation and abolish nuclear β-catenin, providing a mechanism for the loss of dorsal identity in sqt morphants and placing maternal sqt RNA upstream of β-catenin. The loss of early dorsal gene expression can be rescued by the sqt 3'UTR. Our findings identify new non-coding functions for the Nodal genes and support a model wherein sqt RNA acts as a scaffold to bind and deliver/sequester maternal factors to future embryonic dorsal.