Evaluation of the quality of porcine somatic cell nuclear transfer embryo by gene transcription profiles

Positive correlation between the efficiency of induced pluripotent stem cells and the development rate of nuclear transfer embryos when the same porcine embryonic fibroblast lines are used as donor cells

Induced pluripotent stem cells (iPSCs) and nuclear transfer (NT) are two of the primary routes to reprogram differentiated cells back to the pluripotent state. However, it is still unknown whether there is any correlation between the reprogramming efficiency of iPSCs and NT if the same donor cells are employed. In this study, six porcine embryonic fibroblast (PEF) lines from Landrace (L1, L6, L9) or Congjiang local pigs (C4, C5, C6) were used for iPSC induction and NT. Furthermore, the resultant iPSCs from four PEF lines (L1, L6, C4, and C5) were used for NT (iPSC-NT), and the expression of exogenous genes was detected in iPSC-NT embryos by real-time PCR. The results showed that the efficiency of iPSC lines established from different PEF lines were significantly different. When the same PEF lines were used as donor cells for NT, the blastocysts rates were also different among different PEF lines and positively related with iPSCs induction efficiency. When the iPSCs were used as donor cells for NT, compared with the source PEFs, the blastocysts rates were significantly decreased. Real-time PCR results indicated that exogenous genes (Oct4, c-Myc) continued to be expressed in iPSC-NT embryos. In summary, our results demonstrate that there was a positive correlation between iPSCs and NT reprogramming efficiency, although the mechanism of these two routes is different. This may provide a new method to select the appropriate donor cells for inducing iPSCs.

Gene expression profiling of the uterus with embryos cloned by somatic cell nuclear transfer on day 30 of pregnancy

Cloning by somatic cell nuclear transfer (SCNT) in pigs has great value for research and biomedical applications. However, cloning pigs is inefficient, and cloning procedures often lead to the birth of abnormal offspring because of the inadequate nuclear remodeling of donor cells as well as inadequate subsequent development. To understand the problems of the cloning process, it is necessary to understand how the uterus interacts with cloned embryo during pregnancy and supports placentation and fetal development. In this study, we compared gene expression profiles of the uterus with SCNT embryos to those of the uterus with normal embryos by natural mating. We obtained the uterine endometrial tissues on day 30 of pregnancy and conducted gene expression profiling using the Platinum Pig 13K oligonucleotide microarrays. Of the 13,610 genes analyzed, expression of 351 genes significantly increased or decreased in the uterine tissues with SCNT embryos compared to those with normal embryos. The differentially regulated genes included enzymes involved in steroidogenesis and extracellular matrix remodeling and uterine secretory proteins. Analyses of real-time reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization of selected genes confirmed the validity of the gene expression patterns observed in the microarray analysis. Results of this study showed that the transcriptional profile of the genes in the uterus with SCNT embryos was regulated differently indicating that the maternal responsiveness to the SCNT embryos was impaired, resulting in the altered gene expression in the uterus and, in turn, abnormal placental and fetal development and increased embryonic loss.

Expression of X-linked genes in deceased neonates and surviving cloned female piglets

Animal cloning through somatic cell nuclear transfer (NT) is very inefficient, probably due to insufficient reprogramming of the donor nuclei, which in turn would cause the dysregulation of gene expression. X-Chromosome inactivation (XCI) is a multi-step epigenetic process utilized by mammals to achieve dosage compensation in females. Our aim was to determine if any dysregulation of X-linked genes, which would be indicative of unfaithful reprogramming of donor nuclei, was present in cloned pigs. Real time reverse transcription polymerase chain reaction (RT-PCR) was performed to quantify the transcript levels of five X-linked genes, X inactivation-specific transcript (XIST), TSIX (the reverse spelling of XIST), hypoxanthine guanine phosphoribosyltransferase 1 (HPRT1), glucose-6-phosphate dehydrogenase (G6PD), V-raf murine sarcoma 3,611 viral oncogene homolog 1 (ARAF1), and one autosomal gene, alpha-1 type IV collagen (COL4A1) in major organs of neonatal deceased and surviving female cloned pigs as well as their age-matched control pigs from conventional breeding. Aberrant expression level of these genes was prevalent in the neonatal deceased clones, while it was only moderate in cloned pigs that survived after birth. These results suggest a correlation between the viability of the clones and the normality of their gene expression and provide a possible explanation for the death of a large portion of cloned animals around birth.

Differential gene expression patterns in porcine nuclear transfer embryos reconstructed with fetal fibroblasts and mesenchymal stem cells

The present study compared the developmental ability and gene expression pattern at 4-cell, 8-cell, morula, and blastocyst stages of porcine nuclear transfer (NT) embryos from fetal fibroblasts (FFs) and mesenchymal stem cells (MSCs), in vitro fertilized (IVF), and in vivo derived embryos. MSC-NT embryos showed enhanced blastocyst formation, higher total cell number, and a low incidence of apoptosis compared to FF-NT embryos. Alterations in the expression pattern of genes implicated in transcription and pluripotency (Oct4, Stat3, Nanog), DNA methylation (Dnmt1, Dnmt3a), histone deacetylation (Hdac2), growth factor signaling, and imprinting (Igf2, Igf2r) and apoptosis (Bax, Bcl2) regulation were observed in NT embryos. The expression of transcripts in MSC-NT embryos more closely followed that of the in vivo derived embryos compared with FF-NT embryos. In conclusion, MSCs with a relatively undifferentiated genome might serve as suitable donors that could be more efficiently reprogrammed to re-activate expression of early embryonic genes in porcine NT.

Developmental and molecular correlates of bovine preimplantation embryos

Expression of embryonic genes is altered in different culture conditions, which influence developmental potential both during preimplantation and fetal development. The objective of this study was to define the effects of culture conditions on: bovine embryonic development to blastocyst stage, blastocyst cell number, apoptosis and expression patterns of a panel of developmentally important genes. Bovine embryos were cultured in vitro in three culture media containing amino acids, namely potassium simplex optimization medium (KSOMaa), Charles Rosenkrans 1 (CR1aa) and synthetic oviductal fluid (SOFaa). Apoptosis in blastocysts was determined by TUNEL assay and expression profiles of developmentally important genes were assayed by real-time PCR. In vivo-produced bovine blastocysts were used as controls for experiments determining gene expression patterns. While the cleavage rates did not differ, embryos cultured in SOFaa had higher rates of development to blastocyst stage (P < 0.05). Mean cell numbers and percentages of apoptotic cells per blastocyst did not differ among the groups. Expression of the heat shock protein 70 (Hsp70) gene was significantly up-regulated in both CR1aa and KSOMaa when compared with SOFaa (P < 0.001). DNA methyltransferase 3a (Dnmt3a) expression was higher in embryos cultured in CR1aa than in those cultured in SOFaa (P < 0.001). Expression of interferon tau (IF-tau) and insulin-like growth factor II receptor (Igf-2r) genes was significantly up-regulated in KSOMaa when compared with CR1aa (P < 0.001). Gene expression did not differ between in vivo-derived blastocysts and their in vitro-derived counterparts. In conclusion, SOFaa supports higher development to blastocyst stage than KSOMaa and CR1aa, and the culture conditions influence gene expression.

A growth-maturation system that enhances the meiotic and developmental competence of porcine oocytes isolated from small follicles

In livestock, most of the follicles on the ovarian surface are small follicles. A procedure that supports the in vitro growth and maturation of these small follicle-derived oocytes may offer a new source of useable oocytes for both biotechnological and fundamental research purposes. The objective of the current study was to test the hypothesis that providing a more growth-supporting and less maturation-promoting environment during the first phase of small follicle-derived oocyte maturation may improve oocyte competence for meiosis and embryo development upon activation. In our small follicle-derived oocyte growth-maturation system (SGM group), cumulus-oocyte complexes (COCs) from small follicles (1-3 mm) were first cultured in oocyte growth medium for 24 h, then in oocyte maturation medium for 20 h. As controls, COCs from small (SM group) and large (LM group) follicles were cultured using a conventional in vitro maturation (IVM) approach in which they were directly cultured in oocyte maturation medium. At 24 h of culture, the percentage of small follicle-derived oocytes that underwent germinal vesicle breakdown (GVBD) in the SGM group was comparable to that of large follicle-derived oocytes (LM group) but was significantly higher than that of the SM group (P < 0.05). At 44 h of culture, compared to 36% in the SM group, 55% of the SGM group oocytes reached metaphase II (MII; P < 0.05). In addition, the level of cyclin B in oocytes of the SGM group was comparable to that of oocytes from LM group and was significantly higher than that of oocytes from the SM group (P < 0.05). When activated and in vitro fertilized (IVF), 7.3 and 9.0 times more parthenogenetic and IVF embryos developed to blastocyst stage in the SGM group than in the SM group (P < 0.05). The mRNA expression levels of three developmentally important genes--DNA-methyltransferase 1, Pou domain class 5 transcription factor 1, and Fibroblast growth factor receptor 2--in embryos of the SGM group were comparable to those of embryos developed from the LM group, whereas they were significantly lower in those of the SM group (P < 0.05). Our data suggest that the oocyte growth-maturation system facilitates the final stage of oocyte growth and thus resulted in better oocyte nuclear, cytoplasmic maturation, and developmental competency compared with the conventional direct oocyte maturation system.