Document Detail

Segmental assembly of fibronectin matrix requires rap1b and integrin α5.
MedLine Citation:
PMID:  23192979     Owner:  NLM     Status:  Publisher    
BACKGROUND: During segmentation of the zebrafish embryo, inside-out signaling activates Integrin α5, which is necessary for somite border morphogenesis. The direct activator of Integrin α5 during this process is unknown. One candidate is Rap1b, a small monomeric GTPase implicated in Integrin activation in the immune system. RESULTS: Knockdown of rap1b, or overexpression of a dominant negative rap1b, causes a mild axis elongation defect in zebrafish. However, disruption of rap1b function in integrin α5(-/-) mutants results in a strong reduction in Fibronectin (FN) matrix assembly in the paraxial mesoderm and a failure in somite border morphogenesis along the entire anterior-posterior axis. Somite patterning appears unaffected, as her1 oscillations are maintained in single and double morphants/mutants, but somite polarity is gradually lost in itgα5(-/-) ; rap1b MO embryos. CONCLUSIONS: In itgα5(-/-) mutants, rap1b is required for proper somite border morphogenesis in zebrafish. The loss of somite borders is not a result of aberrant segmental patterning. Rather, somite boundary formation initiates but is not completed, due to the failure to assemble FN matrix along the nascent boundary. We propose a model in which Rap1b activates Integrin/Fibronectin receptors as part of an "inside-out" signaling pathway that promotes Integrin binding to FN, FN matrix assembly and subsequent stabilization of morphological somite boundaries. © 2012 Wiley Periodicals, Inc., a Wiley company.
Simone Lackner; Jamie Schwendinger-Schreck; Dörthe Jülich; Scott A Holley
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-29
Journal Detail:
Title:  Developmental dynamics : an official publication of the American Association of Anatomists     Volume:  -     ISSN:  1097-0177     ISO Abbreviation:  Dev. Dyn.     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9201927     Medline TA:  Dev Dyn     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Wiley Periodicals, Inc.
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT.
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