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Functional Cloning Using a Xenopus Oocyte Expression System
Published on: January 30, 2016
Nucleolar re-activation is delayed in mouse embryos cloned from two different cell lines
O Svarcova1, A Dinnyes, Z Polgar
1IBHV, University of Copenhagen, Frederiksberg C, Denmark. osvarcova@gmail.com
Molecular Reproduction and Development
|May 13, 2008
Summary
Embryonic genome activation (EGA) in cloned mouse embryos shows a delay in functional nucleoli development, impacting nucleolar protein targeting and activation. This delay is observed in both mouse embryonic fibroblast (MEF) and HM1 embryonic stem cell nuclear transfer embryos.
Area of Science:
- Developmental Biology
- Cell Biology
- Reproductive Biology
Background:
- Embryonic genome activation (EGA) is a critical step in early development.
- The nucleolus, involved in transcription and ribosome biogenesis, serves as a marker for EGA.
- Understanding nucleolar maturation in different embryo origins is key to assessing developmental potential.
Purpose of the Study:
- To compare embryonic genome activation (EGA) in mouse embryos from various origins.
- To evaluate nucleolar development and function as a marker for EGA.
- To investigate the impact of nuclear transfer on nucleolar maturation.
Main Methods:
- In vitro fertilization (IVF), parthenogenetic activation (PG), and nuclear transfer (NT) using MEF and HM1 ESCs.
- Autoradiography with (3)H-uridine for transcriptional activity.
- Transmission electron microscopy for ultrastructure.
- Immunofluorescence for nucleolar proteins (UBF, B23).
Main Results:
- Early 2-cell embryos showed nucleoplasmic transcription; NPBs were not transcriptionally active.
- Late 2-cell IVF and PG embryos displayed transcription over NPBs, with developing nucleoli.
- NT embryos (MEF and HM1) showed transcription only in nucleoplasm, lacking NPB development into nucleoli.
- By the 4-cell stage, IVF and PG embryos had mature nucleoli, while NT embryos showed delayed maturation.
Conclusions:
- EGA initiates normally in cloned mouse embryos, but functional nucleoli activation is delayed by one cell cycle.
- Nuclear transfer impacts nucleolar protein targeting and activation timing.
- NT-MEF embryos showed delayed protein activation, while NT-HM1 embryos exhibited delays in both targeting and activation.
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