Alkaline phosphatase activity in developing sea urchin eggs

Gustafson, T.; Hasselberg, Ingrid

doi:10.1016/0014-4827(50)90014-0

Cited by 29 publications

(2 citation statements)

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“…In sea urchins the result of LiCl treatment is to cause an exaggeration of vegetal characteristics in developing embryos. It was also reported in 1929 that LiCl induced vegetal structures in isolated animal halves (5); this observation was also made in 1936 by Horstadius (26) (21,23). An increase in the activity of embryo homogenates is seen at mesenchyme blastula, and this increase continues through late pluteus stage.…”

Section: Discussionmentioning

confidence: 48%

Lithium evokes expression of vegetal-specific molecules in the animal blastomeres of sea urchin embryos.

Livingston

Wilt

1989

Proc. Natl. Acad. Sci. U.S.A.

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The mechanism of determination of early embryonic cells has been investigated using sea urchin embryos. An efficacious method of isolating blastomere pairs from the animal or vegetal halfof sea urchin embryos was developed. The overt differentiation of separated animal and vegetal blastomere pairs resembles that of separated animal and vegetal hemispheres isolated by manual dissection. Treatment of animal blastomeres with LiCl caused them to display a morphology resembling that of isolated vegetal blastomeres. The effects of separation of animal and vegetal blastomeres and of treatment of animal blastomeres with LiCl were examined at the molecular level using gut alkaline phosphatase and a spicule matrix protein RNA as markers of differentiation. Histochemical staining and in situ hybridization studies showed that these markers are normally only expressed in vegetal blastomeres but that their expression can be evoked in animal blastomeres by treatment with LiCl.The mechanisms of determination of early embryonic cells are a problem of fundamental importance in biology. Classical studies have shown that the animal and vegetal halves of very early sea urchin embryos are already determined; when separated, the two halves follow widely divergent paths of differentiation. Separated animal halves form hollow epithelial spheres with exaggerated cilia and little overt differentiation. Vegetal halves are able to form more normal embryos with archenterons, skeletal spicules, and pigment cells, which will occasionally go on to form a rather normal pluteus larvae (for reviews, see refs. 1-3).Treatment of embryos with a variety of agents, including LiCl, results in a pattern of differentiation in which archenterons are exaggerated (and/or exogastrulated), and the surface epithelium is reduced. Such embryos are said to be "vegetalized" (4). Von Ubisch (5) reported in 1929 that treatment of the separated animal hemisphere with LiCl resulted in the subsequent formation of guts and spicules by these blastomeres. This result suggests that the capability to form vegetal structures also resides in the animal blastomeres, but in a suppressed or inactive form, and that LiCl may somehow allow vegetal structures to form in blastomeres that have an otherwise quite different determination and fate.LiCI has also been shown to affect cell fate and pattern formation in amphibians (6, 7), suggesting that it alters a cellular process important in determination of cell fate in developing systems. Although LiCl may affect a variety of cellular processes, recent studies showing that LiCl has specific effects on secondary-messenger pathways in several different cell types (8-10) have stimulated our interest in perturbations caused by lithium.We have devised a simple method to study isolated blastomeres in culture that allows one to study the mechanisms of cell determination. The old finding that LiCl may respecify blastomere fate has been confirmed. In addition, we have shown that LiCl not only elicits vegetal structures in animal blastome...

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