Infodoc : Sciences, Techniques et Culture

Reprogramming of a somatic nucleus by nuclear transfer (NT) leads to embryonic stem cells (ESCs) that have been shown to be equivalent to their fertilized (FT) counterparts. However, many embryos display abnormal developmental features after NT, mainly related to defects occuring in the trophoblast. As the cross-talk between trophoblast and epiblast is crucial to the correct patterning and maintenance of the latter, we wondered whether such abnormal reprogramming in the trophoblast may by turn affect the fate of the epiblast. Pluripotent stem cells can also be derived in vitro from the late epiblast of post-implantation embryos. Therefore, we derived and characterized epiblast stem cells from NT embryos (NT-EpiSCs). We showed that FT-EpiSCs and NT-EpiSCs expressed the same set of mark[...]

Reprogramming of a somatic nucleus by nuclear transfer (NT) leads to embryonic stem cells (ESCs) that have been shown to be equivalent to their fertilized (FT) counterparts. However, many embryos display abnormal developmental features after NT, mainly related to defects occuring in the trophoblast. As the cross-talk between trophoblast and epiblast is crucial to the correct patterning and maintenance of the latter, we wondered whether such abnormal reprogramming in the trophoblast may by turn affect the fate of the epiblast. Pluripotent stem cells can also be derived in vitro from the late epiblast of post-implantation embryos. Therefore, we derived and characterized epiblast stem cells from NT embryos (NT-EpiSCs). We showed that FT-EpiSCs and NT-EpiSCs expressed the same set of markers and differentiated in vitro into derivatives of the three lineages. However, gene expression profiles frequently differed between FT and NT-EpiSC, with a majority of differentially expressed genes being down-regulated in the latter. Surprisingly, we observed a bias in the distribution of the dysregulated genes, with about 30% of them localized on chromosome 11. In conclusion, contrary to FT and NT-ESCs that are equivalent at the functional and transcriptional level, EpiSC derivation after nuclear transfer can lead to cell lines incorrectly reprogrammed in which the chromosome 11 seems to be a favorite target of reprogramming errors [...]
La reprogrammation d'un noyau somatique par transfert nucléaire (NT) permet la dérivation de cellules embryonnaires souches (ESCs) qui ont été démontrées comme équivalentes à leurs homologues issues d'embryons fécondés (FT). Cependant, une majorité des embryons clonés par NT souffrent d'anomalies du développement, pour la plupart dues à des défauts dans le trophoblaste. Etant donné que les échanges entre trophoblaste et épiblaste sont cruciaux pour le développement et le maintien de ce dernier, des anomalies dans la reprogrammation du trophoblaste pourraient in fine affecter l'épiblaste. Puisque des cellules souches pluripotentes peuvent être produites in vitro à partir de l'épiblaste d'embryons post-implantatoires, nous avons dérivé et caractérisé des cellules souches épiblastiques (EpiSCs) issues d'embryons clonés (NT-EpiSCs). Nous avons démontré que FT-EpiSCs et NT-EpiSCs exprimaient les mêmes marqueurs et pouvaient être différenciées in vitro en tissus appartenant aux 3 lignages primordiaux. Cependant, l'étude des profils transcriptomiques a fait apparaître des différences entre FT et NT-EpiSCs, avec une majorité de gènes sous-régulés dans ces dernières. De manière surprenante, nous avons pu observer un biais dans la distribution des gènes dé-régulés puisque environ 30% de ceux-ci se situent sur le chromosome 11.