Factors and molecules that could impact cell differentiation in the embryo generated by nuclear transfer

Abstract

Somatic cell nuclear transfer is a technique to create an embryo using an enucleated oocyte and a donor nucleus. Nucleus of somatic cells must be reprogrammed in order to participate in normal development within an enucleated egg. Reprogramming refers to the erasing and remodeling of cellular epigenetic marks to a lower differentiation state. Somatic nuclei must be reprogrammed by factors in the oocyte cytoplasm to a rather totipotent state since the reconstructed embryo must initiate embryo development from the one cell stage to term. In embryos reconstructed by nuclear transfer, the donor genetic material must respond to the cytoplasmic environment of the cytoplast and recapitulate this normal developmental process. Enucleation is critically important for cloning efficiency because may affect the ultrastructure of the remaining cytoplast, thus resulting in a decline or destruction of its cellular compartments. Nonetheless, the effects of in vitro culturing are yet to be fully understood. In vitro oocyte maturation can affect the abundance of specific transcripts and are likely to deplete the developmental competence. The epigenetic modifications established during cellular differentiation are a major factor determining this low efficiency as they act as epigenetic barriers restricting reprogramming of somatic nuclei. In this review we discuss some factors that could impact cell differentiation in embryo generated by nuclear transfer.

Horse ooplasm supports in vitro preimplantation development of zebra ICSI and SCNT embryos without compromising YAP1 and SOX2 expression pattern

“…The low efficiency of SCNT has been primarily attributed to failures during nuclear reprogramming processes, which are necessary to restore the totipotency of the donor somatic cell nucleus [ 51 , 52 ]. In horses, several strategies were recently attempted to improve nuclear reprogramming, but non-significant differences were observed in development [ 53 ].…”

“…Thus, domestic equid females could be used as recipients for SCNT or ICSI zebra embryos, or potentially any other in vitro produced wild equid embryo, opening the possibility to deeply investigate the amazing features of equine pregnancy such as immunological tolerance, placentation, and pregnancy-related endocrinological functions. The low efficiency of SCNT has been primarily attributed to failures during nuclear reprogramming processes, which are necessary to restore the totipotency of the donor somatic cell nucleus [51,52]. In horses, several strategies were recently attempted to improve nuclear reprogramming, but non-significant differences were observed in development [53].…”

Biotechnological bases of the development of cloned pig embryos

“…At somatic cloning, instead of its own chromosomal material, the oocyte (cytoplast) acquires the nucleus of a somatic cell (karyoplast) from the animal, a genetic copy of which is to be obtained. The main stages of the cloning technology included the preparation (in vitro maturation) of the recipient oocyte and donor cells, removing nuclear material from the mature oocyte, reconstruction of the cytoplast obtained (fusion with karyoplasts), activation of the reconstructed oocyte and culture of the cloned embryo (Niemann et al, 2011;Simões, Santos, Jr., 2017).…”