During second cleavage, the macromere with most of the red cytoplasm failed to separate completely at its
vegetal pole (Fig.
Why were muscle cell fates altered in compressed embryos and in small ME embryos produced from the
vegetal pole region, whereas muscle cell fates were normal in ME embryos composed of 40%50% of the total egg volume?
We hypothesize that SpAN operates in sea urchin embryos in a BMP4-like pathway which functions to limit the range of inductive influence emanating from the
vegetal pole. In this way, the SpAN gene, through its regulation by maternal factors, could convert maternal spatial information into regulation of cell signaling along the AV-axis.
A large depression, corresponding to the blastopore, appears at the
vegetal pole 30-35 days after fertilization.
Injections were made within 10 [degrees] arc toward the
vegetal pole from the equator within 6 min after fertilization.
Moreover, three microtubule poisons - colchicine, demecolcine, and nocodazole - inhibit the normal movement of oil droplets toward the
vegetal pole, eliminate the saltatory motion of small inclusions, and slow the growth of the blastodisc: eggs treated with [Beta]-lumicolchicine, an inactive derivative of colchicine, segregated normally (Abraham et al., 1993a).
obs.), with a cap of ooplasm forming at the animal pole and the oil droplets segregating toward the
vegetal pole.
Cells in the
vegetal pole region invaginated in a manner similar to that seen in Boltenia villosa gastrulae.
The results illustrated in Figure 1B (a representative example; n = 12), confirm the earlier findings from the animal pole (3) and the
vegetal pole (2).
We plan to use this technique, in combination with 4-D polarized light microscopy, to observe the behavior of spindles in compressed blastomeres in order to study the precise behavior of the spindle preceding a critical unequal cleavage and to explore the localized distribution of the
vegetal pole determinant.
Oocytes are paired at their
vegetal poles following removal of their vitelline membranes and become electrically coupled via gap junctions.