It is well known that in preimplantation mouse embryos active ribosomal RNA (rRNA) genes are associated with the surface of the so called nucleolar precursor bodies (NPBs), the characteristic structures, which are thought to serve for assembly of the functional nucleolus in early mammalian development. However, the question whether the NPBs are associated with all rDNA repeats and whether the topography of rDNA fluctuates respectively to its transcription and replication status still remains open. We applied fluorescence in situ hybridization with mouse rDNA probes labeled with digoxigenin in order to map rDNA repeats in spreads of two-cell mouse embryos. Our data show: (1) irrespective of the transcriptional activity of rDNA, the NPBs are not equal in their ability to support recruitment of rDNA repeats; (2) a part of rRNA genes is not associated with NPBs, but is "freely" located within the nucleoplasm; (3) resumption of rDNA transcription in late two-cell embryos is accompanied by significant rDNA unraveling as compared with early (transcriptionally inert) two-cell embryos.
|Original language||English (US)|
|Number of pages||8|
|State||Published - Dec 1 2003|
ASJC Scopus subject areas
- Clinical Biochemistry