Localization of Xcat-2 RNA, a putative germ plasm component, to the mitochondrial cloud in Xenopus stage I oocytes

Yi Zhou, Mary Lou King

Research output: Contribution to journalArticlepeer-review

91 Scopus citations


The mitochondrial cloud is a unique cell structure found in stage I Xenopus oocytes that plays a role in mitochondrio-genesis and in the distribution of germ plasm to the vegetal pole. Xcat-2 RNA specifically localizes to the mitochondrial cloud and moves with it to the vegetal subcortex in stage II oocytes. Later, in the 4-cell embryo, it is found in a pattern identical to the germ plasm. Following microinjection into stage I oocytes, synthetic Xcat-2 RNAs localize to the mitochondrial cloud within 22 hours. Transcripts are stable over this time period with very little evidence of degradation. The Xcat-2 3'untranslated region was found to be both required and sufficient for mitochondrial cloud localization. Further deletion analysis narrowed this localization signal to a 250 nucleotide region at the proximal end of the 3'untranslated region. This region is different from, but overlaps with, a domain previously shown to be sufficient to direct Xcat-2 to the vegetal cortex in stage TV oocytes. Examination of early stage I oocytes reveals a time when Xcat-2 is uniformly distributed, arguing against vectorial nuclear export into the mitochondrial cloud. Analysis of localization at different time points does not suggest active transport to the mitochondrial cloud. We postulate that localization occurs by selective entrapment of Xcat-2 within the cloud by localized binding sites.

Original languageEnglish (US)
Pages (from-to)2947-2953
Number of pages7
Issue number9
StatePublished - 1996
Externally publishedYes


  • Germ plasm
  • Localized maternal mRNA
  • Mitochondrial cloud
  • Oocyte
  • Xcat-2
  • Xenopus

ASJC Scopus subject areas

  • Anatomy
  • Cell Biology


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