| Consistent left-right asymmetry cannot be established by late organizers in Xenopus unless the late organizer is a conjoined twin. | |
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MedLine Citation:
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PMID: 20215347 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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How embryos consistently orient asymmetries of the left-right (LR) axis is an intriguing question, as no macroscopic environmental cues reliably distinguish left from right. Especially unclear are the events coordinating LR patterning with the establishment of the dorsoventral (DV) axes and midline determination in early embryos. In frog embryos, consistent physiological and molecular asymmetries manifest by the second cell cleavage; however, models based on extracellular fluid flow at the node predict correct de novo asymmetry orientation during neurulation. We addressed these issues in Xenopus embryos by manipulating the timing and location of dorsal organizer induction: the primary dorsal organizer was ablated by UV irradiation, and a new organizer was induced at various locations, either early, by mechanical rotation, or late, by injection of lithium chloride (at 32 cells) or of the transcription factor XSiamois (which functions after mid-blastula transition). These embryos were then analyzed for the position of three asymmetric organs. Whereas organizers rescued before cleavage properly oriented the LR axis 90% of the time, organizers induced in any position at any time after the 32-cell stage exhibited randomized laterality. Late organizers were unable to correctly orient the LR axis even when placed back in their endogenous location. Strikingly, conjoined twins produced by late induction of ectopic organizers did have normal asymmetry. These data reveal that although correct LR orientation must occur no later than early cleavage stages in singleton embryos, a novel instructive influence from an early organizer can impose normal asymmetry upon late organizers in the same cell field. |
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Authors:
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Laura N Vandenberg; Michael Levin |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Development (Cambridge, England) Volume: 137 ISSN: 1477-9129 ISO Abbreviation: Development Publication Date: 2010 Apr |
Date Detail:
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Created Date: 2010-03-10 Completed Date: 2010-04-09 Revised Date: 2011-07-27 |
Medline Journal Info:
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Nlm Unique ID: 8701744 Medline TA: Development Country: England |
Other Details:
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Languages: eng Pagination: 1095-105 Citation Subset: IM |
Affiliation:
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Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Body Patterning / physiology* Cell Lineage Embryo, Nonmammalian / anatomy & histology, drug effects, physiology, radiation effects Embryonic Induction / physiology Homeodomain Proteins / genetics, metabolism Humans In Situ Hybridization Left-Right Determination Factors / metabolism Lithium Chloride / pharmacology Organizers, Embryonic / drug effects, physiology*, radiation effects Situs Inversus / genetics, metabolism, pathology Twins, Conjoined / embryology* Ultraviolet Rays Xenopus Proteins / genetics, metabolism Xenopus laevis* / anatomy & histology, embryology |
| Grant Support | |
ID/Acronym/Agency:
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1F32GM087107/GM/NIGMS NIH HHS; R01 GM077425/GM/NIGMS NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Homeodomain Proteins; 0/Left-Right Determination Factors; 0/Xenopus Proteins; 0/siamois protein, Xenopus; 7447-41-8/Lithium Chloride |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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