Experimental analysis of second cleavage in the mouse

• Published in: Human reproduction (Oxford) Vol. 17; no. 12; pp. 3178 - 3189
• Main Author: Gardner, R.L.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.12.2002; Oxford Publishing Limited (England)
• Subjects: Animals; Biological and medical sciences; Blastomeres - ultrastructure; Cell Division; Cell Polarity; Cleavage Stage, Ovum; Early stages. Segmentation. Gastrulation. Neurulation; Embryology: invertebrates and vertebrates. Teratology; equatorial division; Female; Fluorescent Dyes; Fundamental and applied biological sciences. Psychology; Gels; meridional division; Mice; Microspheres; mouse conceptuses; regular tetrahedral 4-cell; Rotation; second cleavage; Vitelline Membrane - chemistry; second cleavage; meridional division; mouse conceptuses; equatorial division; regular tetrahedral 4-cell; Embryonic development; Vertebrata; Mammalia; equatorial division/meridional division/mouse conceptuses/regular tetrahedral 4-cell/second cleavage; Mouse; Animal; Rodentia; Cell division; Blastomere; Experimental study
• ISSN: 0268-1161; 1460-2350; 1460-2350
• DOI: 10.1093/humrep/17.12.3178

BACKGROUND: Mammalian conceptuses typically have an approximately regular tetrahedral shape at the 4-cell stage. In the rabbit, this has been attributed to both 2-cell blastomeres dividing meridionally, but with the animal–vegetal axis of the second blastomere to divide rotating through roughly 90° before or during cytokinesis. The aim of the present study was to ascertain whether this was also true for the mouse. METHODS AND RESULTS: First, the distribution in regular tetrahedral 4-cell conceptuses of fluorescent microspheres applied to the vegetal polar region of one or both blastomeres at the 2-cell stage was analysed. Second, the ability of 2-cell stages to form regular tetrahedral 4-cell conceptuses after the previtelline space had been gelated to prevent blastomeres from rotating was also investigated. Neither experiment yielded evidence supporting blastomere rotation during second cleavage. Rather, the findings were consistent with the regular tetrahedral form of 4-cell conceptus resulting from meridional division of one blastomere and approximately equatorial division of the other. CONCLUSIONS: Second cleavage in the mouse typically yields 4-cell conceptuses with three distinct types of blastomere. While both products of the meridional division include all axial levels of the zygote, those of the equatorial division acquire only its vegetal or animal half.