Deregulated Expression of Mitochondrial Proteins Mfn2 and Bcnl3L in Placentae from Sheep Somatic Cell Nuclear Transfer (SCNT) Conceptuses

Abstract

In various animal species, the main cause of pregnancy loss in conceptuses obtained by somatic cell nuclear transfer (SCNT) are placental abnormalities. Most abnormalities described in SCNT pregnancies (such as placentomegaly, reduced vascularisation, hypoplasia of trophoblastic epithelium) suggest that placental cell degeneration may be triggered by mitochondrial failure. We hypothesized that placental abnormalities of clones obtained by SCNT are related to mitochondrial dysfunction. To test this, early SCNT and control (CTR, from pregnancies obtained by in vitro fertilization) placentae were collected from pregnant ewes (at day 20 and 22 of gestation) and subjected to morphological, mRNA and protein analysis. Here, we demonstrated swollen and fragmented mitochondria and low expression of mitofusin 2 (Mfn2), the protein which plays a crucial role in mitochondrial functionality, in SCNT early placentae. Furthermore, reduced expression of the Bcnl3L/Nix protein, which plays a crucial role in selective elimination of damaged mitochondria, was observed and reflected by the accumulation of numerous damaged mitochondria in SCNT placental cells. Likely, this accumulation of damaged organelles led to uncontrolled apoptosis in SCNT placentae, as demonstrated by the high number of apoptotic bodies, fragmented cytoplasm, condensed chromatin, lack of integrity of the nuclear membrane and the perturbed mRNA expression of apoptotic genes (BCL2 and BAX). In conclusion, our data indicate that deregulated expression of Mfn2 and Bcnl3L is responsible for placental abnormalities in SCNT conceptuses. Our results suggest that some nuclear genes, that are involved in the regulation of mitochondrial function, do not work well and consequently this influence the function of mitochondria.

Somatic cell nuclear transfer: failures, successes and the challenges ahead

“…The strategies put forth to improve its efficiency have had a negligible effect in farm animals, and minimal advancements have been achieved only in the mouse. Moreover, the unexpected mitochondrial dysfunctions in cloned embryos, reported for the first time by our group (Czernik et al, 2017), adds a further level of complication to cloning research. Clearly, it appears unlikely that all the biological constraints impairing cloning could be removed by a single treatment/protocol.…”

“…Additionally, it has been shown that low expression of MFN2 in human placentas is associated with mitochondrial damage in placental cells and unexplained miscarriage (Pang et al, 2013). Recently, Czernik et al, (2017) reported that deregulated expression of mitochondrial proteins (MFN2 and BCNL3L) cause abnormalities in early pregnancy placenta in sheep. Abnormalities were mainly presented as damaged and malformed mitochondria, as well as swollen endo-plasmic reticula (Czernik et al, 2017).…”

“…Recently, Czernik et al, (2017) reported that deregulated expression of mitochondrial proteins (MFN2 and BCNL3L) cause abnormalities in early pregnancy placenta in sheep. Abnormalities were mainly presented as damaged and malformed mitochondria, as well as swollen endo-plasmic reticula (Czernik et al, 2017). Similar findings were also reported by Wakisaka and colleagues in mouse cloned placentas (Wakisaka et al, 2008).…”

Animal cloning and consumption of its by-products: A scientific and Islamic perspectives

“…Besides the already existing complications, the unexpected mitochondrial dysfunctions in cloned embryos complicate the cloning process. Thus, it reduces the success rate ( Czernik et al, 2017 ). Several initiatives have, therefore, been implemented to boost the effectiveness of SCNT.…”

CircRNA expression profile of bovine placentas in late gestation with aberrant SCNT fetus

“…Placental research by RNA-seq for abortion and aberrant pregnancy in livestock mainly focused on early gestation or postnatal. [6][7][8][9] little about which However, few studies have looked at the placenta during the third trimester, when large quantity of SCNT fetal abortion occur.…”