Asymmetric inhibition of spicule formation in sea urchin embryos with low concentrations of gadolinium ion

As gastrulation proceeds during sea urchin embryogenesis, primary mesenchyme cells (PMCs) fuse to form syncytial cables, within which calcium is deposited as CaCO₃, and a pair of spicules is formed. Earlier studies suggested that calcium, previously sequestered by primary mesenchyme cells, is secret...

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Bibliographic Details
Published in:	Development, growth & differentiation Vol. 52; no. 9; pp. 735 - 746
Main Authors:	Saitoh, Motoshi, Kuroda, Ritsu, Muranaka, Yoshinori, Uto, Norihiko, Murai, Junko, Kuroda, Hideyo
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Publishing Ltd 01-12-2010
Subjects:	Animals asymmetric spicule formation Dose-Response Relationship, Drug early development Embryo Culture Techniques Embryo, Nonmammalian - drug effects Embryo, Nonmammalian - embryology Gadolinium - pharmacology Ions - pharmacology low concentration of Gd3 sea urchin Sea Urchins - drug effects Sea Urchins - embryology
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Summary:	As gastrulation proceeds during sea urchin embryogenesis, primary mesenchyme cells (PMCs) fuse to form syncytial cables, within which calcium is deposited as CaCO₃, and a pair of spicules is formed. Earlier studies suggested that calcium, previously sequestered by primary mesenchyme cells, is secreted and incorporated into growing spicules. We examined the effects of gadolinium ion (Gd³⁺), a Ca²⁺ channel blocker, on spicule formation. Gd³⁺ did not lead to a retardation of embryogenesis prior to the initiation of gastrulation and did not inhibit the ingression of PMCs from the blastula wall or their migration along the inner blastocoel surface. However, when embryos were raised in seawater containing submicromolar to a few micromolar Gd³⁺, of which levels are considered to be insufficient to block Ca²⁺ channels, a pair of triradiate spicules was formed asymmetrically. At 1-3 μmol/L Gd³⁺, many embryos formed only one spicule on either the left or right side, or embryos formed a very small second spicule. Induction of the spicule abnormality required the presence of Gd³⁺ specifically during late blastula stage prior to spicule formation. An accumulation or adsorption of Gd³⁺ was not detected anywhere in the embryos by X-ray microanalysis, which suggests that Ca²⁺ channels were not inhibited. These results suggest that Gd³⁺ exerts an inhibitory effect on spicule formation through a mechanism that does not involve inhibition of Ca²⁺ channels.
Bibliography:	http://dx.doi.org/10.1111/j.1440-169X.2010.01210.x Present address: 1‐809 Yomogidai, Meito‐ku, Nagoya 465‐0091, Japan. Present address: Shougawa Branch, Tonami City Office, Tonami, Toyama 932‐0393, Japan. Present address: Hamamatsu City Office, Hamamatsu, Shizuoka 430‐8652, Japan. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0012-1592 1440-169X
DOI:	10.1111/j.1440-169X.2010.01210.x