Spatial reorganization of actin, tubulin and histone mRNAs during meiotic maturation and fertilization in Xenopus oocytes.

The distribution of actin, tubulin and histone mRNAs is examined in full grown oocytes, meiotically mature eggs, and unicellular zygotes. For this analysis, oocytes, eggs and embryos were spatially divided into peripheral and central regions of both the animal and vegetal hemispheres, and the relative amounts and concentrations of these RNAs in each region were then determined. The concentration of actin and tubulin mRNAs is greatest in the periphery, whereas histone mRNA exhibits a uniform concentration throughout the oocyte. In the meiotically mature egg, actin mRNA is still concentrated in the periphery and histone mRNA still exhibits a relatively uniform concentration, but the tubulin mRNAs are more concentrated in the central regions. Following fertilization, however, the greatest concentration of mRNAs for actin, histone and tubulin is in the periphery of the zygote. The results demonstrate the existence of a system capable of altering the distributions of these mRNAs as well as a system which distinguishes between different types of mRNA.