Global DNA methylation profiles of buffalo (Bubalus bubalis) preimplantation embryos produced by handmade cloning and in vitro fertilization

Comparative transcriptome profile of embryos at different developmental stages derived from somatic cell nuclear transfer (SCNT) and in-vitro fertilization (IVF) in riverine buffalo (Bubalus bubalis)

Somatic cell nuclear transfer (SCNT) is a very important reproductive technology with many diverse applications, such as fast multiplication of elite animals, the production of transgenic animals and embryonic stem (ES) cells. However, low cloning efficiency, a low live birth rate and the abnormally high incidence of abnormalities in the offspring born are attributed to incomplete or aberrant nuclear reprogramming. In SCNT embryos, the aberrant expression pattern of the genes throughout embryonic development is responsible for the incomplete nuclear reprogramming. The present study was carried out to identify the differential gene expression (DEGs) profile and molecular pathways of the SCNT and IVF embryos at different developmental stages (2 cell, 8 cell and blastocyst stages). In the present study, 1164 (2 cell), 1004 (8 cell) and 530 (blastocyst stage) DEGs were identified in the SCNT embryos as compared to IVF embryos. In addition, several genes such as ZEB1, GDF1, HSF5, PDE3B, VIM, TNNC, HSD3B1, TAGLN, ITGA4 and AGMAT were affecting the development of SCNT embryos as compared to IVF embryos. Further, Gene Ontology (GO) and molecular pathways analysis suggested, SCNT embryos exhibit variations compared to their IVF counterparts and affected the development of embryos throughout the different developmental stages. Apart from this, q-PCR analysis of the GDF1, TMEM114, and IGSF22 genes were utilized to validate the RNA-seq data. These findings contribute valuable insights about the different genes and molecular pathways underlying SCNT embryo development and offer crucial information for improving SCNT efficiency.

High Expression of ZFP42 Improves Early Development of Pig Embryos Produced by Handmade Cloning

Handmade Cloning (HMC) is a pivotal technique for cloning pig embryos. Despite its significance, the low efficiency of this method hampers its widespread application. Although numerous factors and signaling pathways influencing embryo development have been studied, the mechanisms underlying low developmental capacity and insufficient reprogramming of cloned embryos remain elusive. In the present study, we sought to elucidate key regulatory factors involved in the development of pig HMC embryos by comparing and analyzing the gene expression profiles of HMC embryos with those of naturally fertilized (NF) embryos at the 4-cell, 8-cell, and 16-cell stages. The results showed that ZFP42 expression is markedly higher in NF embryos than in cloned counterparts. Subsequent experiments involving the injection of ZFP42 messenger RNA (mRNA) into HMC embryos showed that ZFP42 could enhance the blastocyst formation rate, upregulate pluripotent genes and metabolic pathways. This highlights the potential of ZFP42 as a critical factor in improving the development of pig HMC embryos.

Effect of a low ethanol concentration during in vitro maturation of bovine oocytes and subsequent embryo development

The present study investigated the effects of low ethanol exposure on bovine oocytes. Cumulus-oocyte complexes (COCs) were aspirated for the antral follicles of slaughterhouse-derived ovaries. These COCs were incubated in maturation medium containing 0, 0.1, and 0.2% ethanol for 21 h and subjected to fertilization and in vitro development, and then the rates of nuclear maturation, mitochondrial DNA copy number (Mt-cn) and protein (TOMM40), ATP content and lipid content in oocyte, fertilization, and blastulation were examined. Furthermore, COCs were incubated with 0 or 0.1% ethanol and then mitochondrial membrane potential (MMP) and the glucose consumption of COCs was determined. In addition, gene expression in oocytes was examined by RNA sequencing. Ethanol (0.1 and 0.2%) increased Mt-cn and Mt-protein levels whereas 0.2% ethanol increased the blastulation rate and ATP content in oocytes and decreased lipid content in oocytes. Ethanol (0.1%) increased MMP in oocytes and decreased glucose consumption of COCs. Eight stage embryos derived from 0.1% ethanol treated oocytes had higher levels of trimethyl-H3K9 compared with that of nontreated counterpart. RNA sequencing revealed that differentially expressed genes were associated with glycolysis/gluconeogenesis, carbon metabolism, sphingolipid metabolism, amino acid metabolism, and fatty acid degradation pathways. In conclusion, even 0.1% concentrations of ethanol during in vitro maturation considerably affects oocyte metabolism and histone configuration of embryos.

Epigenetic manipulation to improve mouse SCNT embryonic development

Cloned mammals can be achieved through somatic cell nuclear transfer (SCNT), which involves reprogramming of differentiated somatic cells into a totipotent state. However, low cloning efficiency hampers its application severely. Cloned embryos have the same DNA as donor somatic cells. Therefore, incomplete epigenetic reprogramming accounts for low development of cloned embryos. In this review, we describe recent epigenetic barriers in SCNT embryos and strategies to correct these epigenetic defects and avoid the occurrence of abnormalities in cloned animals.