Pearls Are Novel Cajal Body-Like Structures in the Xenopus Germinal Vesicle That Are Dependent on RNA Pol III Transcription

Chromosome Res. 2012 Dec;20(8):953-69. doi: 10.1007/s10577-012-9320-1.


We have identified novel nuclear bodies, which we call pearls, in the giant oocyte nuclei of Xenopus laevis and Xenopus tropicalis. Pearls are attached to the lampbrush chromosomes at specific loci that are transcribed by RNA polymerase III, and they disappear after inhibition of polymerase III activity. Pearls are enriched for small Cajal body-specific RNAs (scaRNAs), which are guide RNAs that modify specific nucleotides on splicing snRNAs. Surprisingly, snRNAs themselves are not present in pearls, suggesting that pearls are not functionally equivalent to Cajal bodies in other systems, which contain both snRNAs and scaRNAs. We suggest that pearls may function in the processing of RNA polymerase III transcripts, such as tRNA, 5S rRNA, and other short non-coding RNAs.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Blotting, Western
  • Chromosomes / genetics
  • Chromosomes / ultrastructure
  • Cloning, Molecular
  • Coiled Bodies / genetics*
  • Coiled Bodies / ultrastructure
  • Genetic Loci
  • In Situ Hybridization, Fluorescence
  • Oocytes / cytology
  • Oocytes / metabolism
  • RNA / analysis*
  • RNA / genetics
  • RNA / metabolism
  • RNA Polymerase III / genetics*
  • RNA Polymerase III / metabolism
  • RNA Splicing
  • RNA, Ribosomal, 5S / genetics
  • RNA, Ribosomal, 5S / metabolism
  • RNA, Small Nucleolar / genetics
  • RNA, Small Nucleolar / metabolism
  • Transcription, Genetic
  • Xenopus laevis / genetics*


  • RNA, Ribosomal, 5S
  • RNA, Small Nucleolar
  • RNA, U3 small nucleolar
  • RNA
  • RNA Polymerase III