The spatial pattern of RNA in fully grown oocytes of an amphibian, Xenopus laevis.

The possibility that maternal RNA may be localized in specific oocyte regions was examined in fully grown oocytes of Xenopus laevis. These oocytes were subdivided into six regions perpendicular to their animal-vegetal axis. Each region was analyzed to determine the amount of total cellular RNA, poly(A)+RNA, and newly synthesized ribosomal RNA. As would be expected from current evidence, total cellular RNA was found to exist in a gradient-like fashion, highest at the animal pole and lowest at the vegetal pole. However, poly(A)+RNA and newly synthesized ribosomal RNA had significantly different spatial patterns from each other and from total cellular RNA. In addition, evidence suggests that newly synthesized ribosomal RNA requires two to three days before it is uniformly distributed within the oocyte. These results suggest that a mechanism may exist to create different spatial patterns for different classes of RNA.