Theoretical exploration of blastocyst morphogenesis

摘要

A theoretical exploration of cell distribution on the mouse blastocyst is conducted.A model ball of cells represents the morula which develops into a 32-cell model blastocyst that isenclosed in a spherical surface with a hemispherical cavity at one end. In the combinatorialanalysis it is assumed that each cell of the 2-cell embryo forms 16 cells in the blastocyst and thatthese 16 cells touch each other. The results of the analysis identify a tendency for one set of 16 cellsto contribute twice as many cells to the basal solid end of the blastocyst than the other set, adevelopmental bias that is also found by some observers of natural blastocysts. In the geometricanalysis, half the volume of the inner group of cells of the morula and blastocyst and half thevolume of the surrounding shell cells, the trophectoderm, is assumed to be formed from theprogeny of each 2-cell stage cell. Making various assumptions about morphogenesis, it is foundthat there is a tendency for a curved frontier between the volumes from each 2-cell stage cell, theclonal volumes, to lie at an angle of 43.4° to the equator of the blastocyst and for the bulk of thefrontier circumference to lie on either side of the equator. These tendencies are also found by someobservers of real blastocysts.