Nucleologenesis and embryonic genome activation are defective in interspecies cloned embryos between bovine ooplasm and rhesus monkey somatic cells.
BACKGROUND
Interspecies somatic cell nuclear transfer (iSCNT) has been proposed as a tool to address basic developmental questions and to improve the feasibility of cell therapy. However, the low efficiency of iSCNT embryonic development is a crucial problem when compared to in vitro fertilization (IVF) and intraspecies SCNT. Thus, we examined the effect of donor cell species on the early development of SCNT embryos after reconstruction with bovine ooplasm.


RESULTS
No apparent difference in cleavage rate was found among IVF, monkey-bovine (MB)-iSCNT, and bovine-bovine (BB)-SCNT embryos. However, MB-iSCNT embryos failed to develop beyond the 8- or 16-cell stages and lacked expression of the genes involved in embryonic genome activation (EGA) at the 8-cell stage. From ultrastructural observations made during the peri-EGA period using transmission electron microscopy (TEM), we found that the nucleoli of MB-iSCNT embryos were morphologically abnormal or arrested at the primary stage of nucleologenesis. Consistent with the TEM analysis, nucleolar component proteins, such as upstream binding transcription factor, fibrillarin, nucleolin, and nucleophosmin, showed decreased expression and were structurally disorganized in MB-iSCNT embryos compared to IVF and BB-SCNT embryos, as revealed by real-time PCR and immunofluorescence confocal laser scanning microscopy, respectively.


CONCLUSIONS
The down-regulation of housekeeping and imprinting genes, abnormal nucleolar morphology, and aberrant patterns of nucleolar proteins during EGA resulted in developmental failure in MB-iSCNT embryos. These results provide insight into the unresolved problems of early embryonic development in iSCNT embryos.
Song
Bong-Seok
BS
Development and Differentiation Research Center, Korea Research Institute of Bioscience and Biotechnology, Gwahangno, Yuseong-gu, Daejeon, Republic of Korea. sbs6401@hanmail.net
Lee
Sang-Hee
SH
Kim
Sun-Uk
SU
Kim
Ji-Su
JS
Park
Jung Sun
JS
Kim
Cheol-Hee
CH
Chang
Kyu-Tae
KT
Han
Yong-Mahn
YM
Lee
Kyung-Kwang
KK
Lee
Dong-Seok
DS
Koo
Deog-Bon
DB
D000818:Animals; D002417:Cattle / Q000196:embryology*; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism; D047108:Embryonic Development; D016678:Genome; D008253:Macaca mulatta / Q000196:embryology*; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000166:cytology