Aberrant allocations of inner cell mass and trophectoderm cells in bovine nuclear transfer blastocysts.
Abortions of nuclear transfer (NT) embryos are mainly due to insufficient placentation. We hypothesized that the primary cause might be the aberrant allocations of two different cell lineages of the blastocyst stage embryos, the inner cell mass (ICM) and the trophectoderm (TE) cells. The potential for development of NT embryos to blastocysts was similar to that for in vitro fertilized (IVF) embryos. No difference in the total cell number was detected between NT and IVF blastocysts, but both types of embryos had fewer total cells than did in vivo-derived embryos (P < 0.05). The NT blastocysts showed a higher ratio of ICM:total cells than did IVF or in vivo-derived embryos (P < 0.05). Individual blastocysts were assigned to four subgroups (I: <20%, II: 20-40%, III: 40-60%, IV: >60%) according to the ratio of ICM:total cells. Most NT blastocysts were placed in groups III and IV, whereas most IVF and in vivo-derived blastocysts were distributed in group II. Our findings suggest that placental abnormalities or early fetal losses in the present cloning system may be due to aberrant allocations of NT embryos to the ICM and TE cells during early development.
Animal Developmental Biotechnology Laboratory, Korea Research Institute of Bioscience and Biotechnology, Yusong, Daejeon 305-600, Korea.
Deog-Bon
DB
Koo
Yong-Kook
YK
Kang
Young-Hee
YH
Choi
Jung Sun
JS
Park
Ha-Na
HN
Kim
Keon Bong
KB
Oh
Dong-Soo
DS
Son
Humdai
H
Park
Kyung-Kwang
KK
Lee
Yong-Mahn
YM
Han
D000818:Animals; D001755:Blastocyst / Q000166:cytology*; D002417:Cattle; D002452:Cell Count; D002467:Cell Nucleus / Q000235:genetics*; D004396:Coloring Agents; D003470:Culture Media; D004475:Ectoderm / Q000166:cytology*; D010064:Embryo Implantation / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro; D066298:In Vitro Techniques; D009865:Oocytes / Q000502:physiology; D010920:Placenta / Q000502:physiology; D011247:Pregnancy; D014327:Trophoblasts / Q000166:cytology*
D004396:Coloring Agents; D003470:Culture Media