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The establishment of bilateral asymmetry in sea urchin embryos

Authors :
McCain, Elizabeth R.
McClay, David R.
Source :
Development; February 1994, Vol. 120 Issue: 2 p395-404, 10p
Publication Year :
1994

Abstract

Although much is known about the specification and determination of the two primary axes (animal/vegetal and dorsoventral or oral/aboral) in a number of embryos, little is understood about bilaterality. In the sea urchin, left/right asymmetry is crucial to normal development as the echinus or adult rudiment is positioned on the left side of the larva. We examined the establishment of bilateral asymmetry in Lytechnis variegatus embryos by determining the relationship of the first cleavage planes to the left/right axis. Embryos were bisected at different times to determine when the bilateral axis is committed. These lineage tracing and cell separation experiments demonstrated that the first cleavage plane divides the embryo into left and right halves, although this is conditional until after late blastula stage. The relationship between the specification of the dorsoventral axis and the bilateral axis was examined experimentally. In other species when the dorsal and ventral halves of early echinoderm embryos (preblastula) are separated, the dorsal half often reverses (180°) its dorsoventral axis. We asked whether those larvae with an inverted dorsoventral axis would shift the position of the echinus rudiment from the original left side to the new left side. If so, it would demonstrate that the larval asymmetry is dependent upon specification of the dorsoventral axis. Using a combination of lineage tracing and cell separation techniques, we show that the left/right asymmetry is specified with respect to the dorsoventral axis.

Details

Language :
English
ISSN :
09501991 and 14779129
Volume :
120
Issue :
2
Database :
Supplemental Index
Journal :
Development
Publication Type :
Periodical
Accession number :
ejs59001141
Full Text :
https://doi.org/10.1242/dev.120.2.395