Uncoupled embryonic and extra-embryonic tissues compromise blastocyst development after somatic cell nuclear transfer.
Somatic cell nuclear transfer (SCNT) is the most efficient cell reprogramming technique available, especially when working with bovine species. Although SCNT blastocysts performed equally well or better than controls in the weeks following embryo transfer at Day 7, elongation and gastrulation defects were observed prior to implantation. To understand the developmental implications of embryonic/extra-embryonic interactions, the morphological and molecular features of elongating and gastrulating tissues were analysed. At Day 18, 30 SCNT conceptuses were compared to 20 controls (AI and IVP: 10 conceptuses each); one-half of the SCNT conceptuses appeared normal while the other half showed signs of atypical elongation and gastrulation. SCNT was also associated with a high incidence of discordance in embryonic and extra-embryonic patterns, as evidenced by morphological and molecular "uncoupling". Elongation appeared to be secondarily affected; only 3 of 30 conceptuses had abnormally elongated shapes and there were very few differences in gene expression when they were compared to the controls. However, some of these differences could be linked to defects in microvilli formation or extracellular matrix composition and could thus impact extra-embryonic functions. In contrast to elongation, gastrulation stages included embryonic defects that likely affected the hypoblast, the epiblast, or the early stages of their differentiation. When taking into account SCNT conceptus somatic origin, i.e. the reprogramming efficiency of each bovine ear fibroblast (Low: 0029, Med: 7711, High: 5538), we found that embryonic abnormalities or severe embryonic/extra-embryonic uncoupling were more tightly correlated to embryo loss at implantation than were elongation defects. Alternatively, extra-embryonic differences between SCNT and control conceptuses at Day 18 were related to molecular plasticity (high efficiency/high plasticity) and subsequent pregnancy loss. Finally, because it alters re-differentiation processes in vivo, SCNT reprogramming highlights temporally and spatially restricted interactions among cells and tissues in a unique way.
INRA, UMR 1198 Biologie du Développement et Reproduction, Jouy-en-Josas, France.
Séverine A
SA
Degrelle
Florence
F
Jaffrezic
Evelyne
E
Campion
Kim-Anh
KA
Lê Cao
Daniel
D
Le Bourhis
Christophe
C
Richard
Nathalie
N
Rodde
Renaud
R
Fleurot
Robin E
RE
Everts
Jérôme
J
Lecardonnel
Yvan
Y
Heyman
Xavier
X
Vignon
Xiangzhong
X
Yang
Xiuchun C
XC
Tian
Harris A
HA
Lewin
Jean-Paul
JP
Renard
Isabelle
I
Hue
D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D016022:Case-Control Studies; D002417:Cattle; D002450:Cell Communication / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D004624:Embryo Transfer / Q000662:veterinary; D047108:Embryonic Development / Q000502:physiology*; D005321:Extraembryonic Membranes / Q000503:physiopathology* / Q000648:ultrastructure; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D053263:Gene Regulatory Networks / Q000235:genetics; D017403:In Situ Hybridization / Q000662:veterinary; D008855:Microscopy, Electron, Scanning / Q000662:veterinary; D053652:Nuclear Transfer Techniques / Q000009:adverse effects / Q000662:veterinary*; D011247:Pregnancy; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D012732:Sex Determination Analysis / Q000662:veterinary
D017931:DNA Primers