Sato E (2014), Twin Xenopus laevis embryos appearing from flat...

XB-ART-49501

Proc Jpn Acad Ser B Phys Biol Sci 2014 Jan 01;908:307-12. doi: 10.2183/pjab.90.307.

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Twin Xenopus laevis embryos appearing from flattened eggs.

Sato E .

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Remarkable progress has recently been made in molecular biology of double axis formation in Xenopus laevis. Leaving aside, for the time being, the problem of the gene expressions regulating Xenopus laevis development, here I show that pulse treatment could induce formation of a secondary axis in a fertilized Xenopus laevis egg. At 3 min after insemination, metal oxides were added to Xenopus fertilized eggs, and then twin embryos appeared. Zirconium oxide (ZrO2) was the most effective metal oxide for producing twin embryos. ZrO2 was added to the fertilized eggs, and 30 sec later, the eggs were dejellied with cysteine solution and washed within 7 min after insemination. The fertilized eggs began flattening at around 15 min after insemination. When the degree of flattening (the vertical length of the egg divided by the horizontal length) of the eggs at the 16- and 32-cell stages became less than 0.4 degrees, production of twin embryos occurred. Many flattened eggs at less than 0.4 degrees formed twin embryos. The third cleavage of eggs treated with metal oxides was meridional, while the normal third cleavage was horizontal.

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Species referenced: Xenopus laevis
Genes referenced: sia2

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	Figure 1. . Successive change of Xenopus embryos treated with ZrO2 at 3 min after insemination and schematic process of development. a, 8-cell; b, 16-cell; c, blastula; d, neurula; e, tail bud; f, tadpole; Bar length: 1.0 mm.
	Figure 2. . Schematic representation of top view about normal and metal oxides treated eggs development, pictures cited and modified from the textbook.17) Usual dejellying procedure is done at 10–40 min after insemination. My unusual dejellying started at 3 min and 30 sec after insemination. Abbreviations, St. 2: two cell stage, St. 4: eight cell stage, St. 5: sixteen cell stage, St. 13: initial neural plate stage, St. 22: early tail bud stage, ap: animal pole, vp: vegetative pole, nf: neural fold, eyv: eye vesicle, cg: cement gland.
	Figure 3. . Side view of flattening egg at 16-cell stage. White arrowhead indicates top of egg and black arrowhead indicates bottom of egg. Bar length: 1.0 mm a. Control egg. The eggs are supported by forceps to show vegetal half of eggs and measure length of egg on the ruler. b. ZrO2 treated egg is supported by forceps to show vegetal half of egg and measure length of egg.
	Figure 4. . Vertical and horizontal length of eggs. a. The open circles represent control eggs. The filled circles represent flattened eggs treated with ZrO2 at 3 min after insemination. b. The ratios of vertical length/horizontal length are shown, control eggs (n = 19) and ZrO2 treated eggs (n = 31). The values are expressed as the means ± SD.
	Figure 5. . The abscissa records the time of ZrO2 treatment for fertilized eggs, normalized to first cleavage and real time after insemination. Twinning frequency is reduced after 0.07. The open circles represent average twinning frequencies of egg batches from different frogs. The data for each circle are from 21–73 eggs from one frog.

References [+] :

Black, High-frequency twinning of Xenopus laevis embryos from eggs centrifuged before first cleavage. 1986, Pubmed, Xenbase