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Numerical chromosome errors in day 7 somatic nuclear transfer bovine blastocysts
Paul J Booth1, Dorthe Viuff, Shijian Tan
1Section of Reproductive Biology, Department of Animal Breeding and Genetics, Danish Institute of Agricultural Sciences, 8830 Tjele, Denmark. chpabo@vestamt.dk
Biology of Reproduction
|February 27, 2003
Summary
Somatic nuclear transfer (NT) in cattle produces a high rate of mixoploid embryos, with tetraploidy being the most common abnormality. These ploidy errors are not linked to donor granulosa cells but inversely correlate with blastocyst cell number.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Genetics
Background:
- Somatic nuclear transfer (NT) in cattle is associated with significant embryonic and fetal loss.
- Numerical chromosome aberrations are a suspected cause of this reproductive inefficiency.
Purpose of the Study:
- To investigate the frequency and nature of numerical chromosome aberrations in bovine somatic NT embryos.
- To determine if ploidy errors originate from donor granulosa cells.
Main Methods:
- Bovine NT embryos were reconstructed using a zona-free method with granulosa cells.
- Embryos were cultured for 7 days, and nuclei were extracted for chromosome analysis.
- Dual-color fluorescent in situ hybridization (FISH) was used to evaluate chromosome aberrations (ploidy errors).
Main Results:
- A high incidence of mixoploidy (73.7%) and tetraploidy (10.0%) was observed in NT blastocysts.
- Ploidy distributions varied significantly between embryo clone families.
- Blastocyst quality was negatively correlated with the percentage of chromosome abnormalities.
Conclusions:
- Ploidy errors in bovine NT blastocysts are common, with mixoploidy being prevalent.
- The observed ploidy errors do not appear to originate from the donor granulosa cells.
- Chromosome abnormalities are inversely related to blastocyst cell number and embryo quality.