Improving heterochromatin remodelling of cloned embryos: a key to cloning efficiency?
Résumé
The organization of centromeric and pericentric heterochromatin in 1-cell fertilized mouse embryos is completely different from the organization observed in somatic cells. This unique organization is also observed in 60% of embryos obtained by nuclear transfer using embryonic stem cell (ESNT). Here, we show that remodelling into a zygotic-like organization also occurs after somatic cell nuclear transfer (SCNT), supporting the hypothesis that reorganization of constitutive heterochromatin can occur regardless of the source and differentiation state of the starting material. However, remodelling efficiency in SCNT embryos appears lower than in ESNT embryos and is accompanied by a lower developmental potential. Interestingly, treatment of SCNT embryos with the deacetylase inhibitor trichostatin A (TSA)improves nuclear remodelling at the first cell stage as well as development to term, but not to blastocyst. Together, the results suggest that proper organization of constitutive heterochromatin in early embryos has long-term effects, especially in cloning procedures.