Early left‐right asymmetries during axial morphogenesis in the chick embryo. Issue 6 (5th April 2014)

• Record Type: Journal Article
• Authors: Otto, Annalena; Pieper, Tobias; Viebahn, Christoph; Tsikolia, Nikoloz; Halpern, Marnie E.; Hobert, Oliver; Wright, Christopher V. E.
• Is Part Of: Genesis. Volume 52:Issue 6(2014:Jun.)
• Page Start: 614
• Page End: 625
• Publication Date: 2014-04-05
• Subjects: Developmental genetics -- Periodicals; Genetics -- Periodicals; Developmental biology -- Periodicals; Embryology -- Periodicals; Genetic regulation -- Periodicals; 576.5
• DOI: 10.1002/dvg.22773
• Languages: English
• ISSNs: 1526-954X

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>The primitive node is the "hub" of early left‐right patterning in the chick embryo: (1) it undergoes asymmetrical morphogenesis immediately after its appearance at Stage 4; (2) it is closely linked to the emerging asymmetrical expression of <italic>nodal</italic> and <italic>shh</italic> at Stage 5; and (3) its asymmetry is spatiotemporally related to the emerging notochord, the midline barrier maintaining molecular left‐right patterning from Stage 6 onward. Here, we study the correlation of node asymmetry to notochord marker expression using high‐resolution histology, and we test pharmacological inhibition of shh signaling using cyclopamine at Stages 4 and 5. Just as <italic>noggin</italic> expression mirrors an intriguing structural continuity between the right node shoulder and the notochord, <italic>shh</italic> expression in the left node shoulder confirms a similar continuity with the future floor plate. Shh inhibition at Stage 4 or 5 suppressed <italic>nodal</italic> in both its paraxial or lateral plate mesoderm domains, respectively, and resulted in randomized heart looping. Thus, the "primordial" paraxial <italic>nodal</italic> asymmetry at Stage 4/5 (1) appears to be dependent on, but not instructed by, shh signaling and (2) may be fixed by asymmetrical roots of the notochord and the floor plate, thereby adding further twists to the node's pivotal role during left‐right patterning. genesis 52:614–625, 2014. © 2014 Wiley Periodicals, Inc.</p> </abstract>