Does supplementation of oocytes with additional mtDNA influence developmental outcome?

Introducing extra mitochondrial DNA (mtDNA) into oocytes at fertilization can rescue poor quality oocytes. However, supplementation alters DNA methylation and gene expression profiles of preimplantation embryos. To determine if these alterations impacted offspring, we introduced mtDNA from failed-to-mature sister (autologous) or third party (heterologous) oocytes into mature oocytes and transferred zygotes into surrogates. Founders exhibited significantly greater daily weight gain (heterologous) and growth rates (heterologous and autologous) to controls. In weaners, cholesterol, bilirubin (heterologous and autologous), anion gap, and lymphocyte count (autologous) were elevated. In mature pigs, potassium (heterologous) and bicarbonate (autologous) were altered. mtDNA and imprinted gene analyses did not reveal aberrant profiles. Neither group exhibited gross anatomical, morphological, or histopathological differences that would lead to clinically significant lesions. Female founders were fertile and their offspring exhibited modified weight and height gain, biochemical, and hematological profiles. mtDNA supplementation induced minor differences that did not affect health and well-being.

Differential Methylation and Transcriptome Integration Analysis Identified Differential Methylation Annotation Genes and Functional Research Related to Hair Follicle Development in Sheep

Hair follicle growth and development are a complex and long-term physiological process, which is regulated by a variety of physical factors and signal pathways. Increasing the understanding of the epigenetic regulation and function of candidate genes related to hair follicle development will help to better understand the molecular regulatory mechanisms of hair follicle development. In this study, the methylated DNA immunoprecipitation sequencing (MeDIP-seq) was used to obtain the genome-wide methylation map of the hair follicular development of Super Merino sheep in six stages (fetal skin tissue at 65d, 85d, 105d, 135d, 7d, and 30d after birth). Combined with the results of previous RNA-sequencing, 65 genes were screened out that were both differential methylation and differential expression, including EDN1, LAMC2, NR1D1, RORB, MyOZ3, and WNT2 gene. Differential methylation genes were enriched in Wnt, TNF, TGF-beta, and other signaling pathways related to hair follicle development. The bisulfite sequencing PCR results and MeDIP-seq were basically consistent, indicating that the sequencing results were accurate. As a key gene in the Wnt signaling pathway, both differential methylation and expression gene identified by MeDIP-seq and RNA-seq, further exploration of the function of WNT2 gene revealed that the DNA methylation of exon 5 (CpG11 site) promoted the expression of WNT2 gene. The overexpression vector of lentivirus pLEX-MCS-WNT2 was constructed, and WNT2 gene effectively promoted the proliferation of sheep skin fibroblasts. The results showed that WNT2 gene could promote the growth and development of skin and hair follicles. The results of this study will provide a theoretical basis for further research on sheep hair follicle development and gene regulation mechanisms.

Genome-wide DNA methylation and transcription analysis in tongue and biceps femoris muscles of cloned pigs with macroglossia

Cloned animals are prone to abnormal phenotypes such as enlarged tongue, fetal oversize, and progeria. In the present study, whole-genome bisulfite sequencing and mRNA sequencing were performed on tongue and biceps femoris muscles of cloned piglets with and without macroglossia, in an attempt to elucidate the epigenetic causes of the macroglossia phenotype. We identified 14 958 and 18 752 differentially methylated regions in the tongue and biceps femoris muscles, respectively, of macroglossia piglets and these correspond to 4574 and 4772 differentially methylated genes compared with the control group (piglets without macroglossia). Larger methylation difference was found in tongue muscle than in biceps femoris muscle. In total, 114 genes in tongue and 72 genes in biceps femoris muscles were found to be differentially expressed between the two groups. Of these differentially expressed genes in tongue muscle, 31 were also differentially methylated genes, among which DIO3 and ZIC1 were imprinting or predicted imprinting genes. These two and another six overlapping genes (ALDH1A2, MKX, MAB21L2, CA3, RANBP3L, and MYL10) are crucial factors involved in embryonic development or tissue and organ development. GO enrichment analysis suggested possible alteration of these processes. Our study provides novel molecular insights into the formation of macroglossia in cloned pigs.

Assessment of the Growth and Reproductive Performance of Cloned Pietrain Boars

How to maximize the use of the genetic merits of the high-ranking boars (also called superior ones) is a considerable question in the pig breeding industry, considering the money and time spent on selection. Somatic cell nuclear transfer (SCNT) is one of the potential ways to answer the question, which can be applied to produce clones with genetic resources of superior boar for the production of commercial pigs. For practical application, it is essential to investigate whether the clones and their progeny keep behaving better than the "normal boars", considering that in vitro culture and transfer manipulation would cause a series of harmful effects to the development of clones. In this study, 59,061 cloned embryos were transferred into 250 recipient sows to produce the clones of superior Pietrain boars. The growth performance of 12 clones and 36 non-clones and the semen quality of 19 clones and 28 non-clones were compared. The reproductive performance of 21 clones and 25 non-clones were also tested. Furthermore, we made a comparison in the growth performance between 466 progeny of the clones and 822 progeny of the non-clones. Our results showed that no significant difference in semen quality and reproductive performance was observed between the clones and the non-clones, although the clones grew slower and exhibited smaller body size than the non-clones. The F1 progeny of the clones showed a greater growth rate than the non-clones. Our results demonstrated through the large animal population showed that SCNT manipulation resulted in a low growth rate and small body size, but the clones could normally produce F1 progeny with excellent growth traits to bring more economic benefits. Therefore, SCNT could be effective in enlarging the merit genetics of the superior boars and increasing the economic benefits in pig reproduction and breeding.

Whole-Genome Methylation Analysis Reveals Epigenetic Variation in Cloned and Donor Pigs

Somatic cloning has had a significant impact on the life sciences and is important in a variety of processes, including medical research and animal production. However, the application of somatic cloning has been limited due to its low success rate. Therefore, potential epigenetic variations between cloned and donor animals are still unclear. DNA methylation, one of the factors which is responsible for phenotypic differences in animals, is a commonly researched topic in epigenetic studies of mammals. To investigate the epigenetic variations between cloned and donor animals, we selected blood and ear fibroblasts of a donor pig and a cloned pig to perform whole-genome bisulfite sequencing (WGBS). A total of 215 and 707 differential methylation genes (DMGs) were identified in blood and ear fibroblasts, respectively. Functional annotation revealed that DMGs are enriched in many pathways, including T/B or natural killer (NK) cell differentiation, oocyte maturation, embryonic development, and reproductive hormone secretion. Moreover, 22 DMGs in the blood and 75 in the ear were associated with immune responses (e.g., CD244, CDK6, CD5, CD2, CD83, and CDC7). We also found that 18 DMGs in blood and 53 in ear fibroblasts were involved in reproduction. Understanding the expression patterns of DMGs, especially in relation to immune responses and reproduction, will reveal insights that will aid the advancement of future somatic cloning techniques in swine.

Characterization and comparative analyses of transcriptomes of cloned and in vivo fertilized porcine pre-implantation embryos

Somatic cell nuclear transfer (SCNT) is the only method known to rapidly reprogram differentiated cells into totipotent embryos. Most cloned embryos become arrested before implantation and the details of the underlying molecular mechanism remain largely unknown. Dynamic regulation of the transcriptome is a key molecular mechanism driving early embryonic development. Here, we report comprehensive transcriptomic analysis of cloned embryos (from Laiwu and Duroc pigs) and in vivo fertilized embryos (from Duroc pigs) using RNA-sequencing. Comparisons between gene expression patterns were performed according to differentially expressed genes, specific-expressed genes, first-expressed genes, pluripotency genes and pathway enrichment analysis. In addition, we closely analyzed the improperly expressed histone lysine methyltransferases and histone lysine demethylases during cell reprogramming in cloned embryos. In summary, we identified altered gene expression profiles in porcine cloned pre-implantation embryos in comparison to normal in vivo embryos. Our findings provide a substantial framework for further discovery of the epigenetic reprogramming mechanisms in porcine SCNT embryos.

Summary: Comparative transcriptome analyses of cloned and in vivo fertilized pre-implantation embryos: transcriptional defects and reprogramming barriers in porcine somatic cell nuclear reprogramming.

Genome-wide DNA methylation profiles in Tibetan and Yorkshire pigs under high-altitude hypoxia

Background

Tibetan pigs, which inhabit the Tibetan Plateau, exhibit distinct phenotypic and physiological characteristics from those of lowland pigs and have adapted well to the extreme conditions at high altitude. However, the genetic and epigenetic mechanisms of hypoxic adaptation in animals remain unclear.

Methods

Whole-genome DNA methylation data were generated for heart tissues of Tibetan pigs grown in the highland (TH, n = 4) and lowland (TL, n = 4), as well as Yorkshire pigs grown in the highland (YH, n = 4) and lowland (YL, n = 4), using methylated DNA immunoprecipitation sequencing.

Results

We obtained 480 million reads and detected 280679, 287224, 259066, and 332078 methylation enrichment peaks in TH, YH, TL, and YL, respectively. Pairwise TH vs. YH, TL vs. YL, TH vs. TL, and YH vs. YL comparisons revealed 6829, 11997, 2828, and 1286 differentially methylated regions (DMRs), respectively. These DMRs contained 384, 619, 192, and 92 differentially methylated genes (DMGs), respectively. DMGs that were enriched in the hypoxia-inducible factor 1 signaling pathway and pathways involved in cancer and hypoxia-related processes were considered to be important candidate genes for high-altitude adaptation in Tibetan pigs.

Conclusions

This study elucidates the molecular and epigenetic mechanisms involved in hypoxic adaptation in pigs and may help further understand human hypoxia-related diseases.

Transcriptome analysis reveals long intergenic non-coding RNAs involved in skeletal muscle growth and development in pig

Long intergenic non-coding RNAs (lincRNAs) play essential roles in numerous biological processes and are widely studied. The skeletal muscle is an important tissue that plays an essential role in individual movement ability. However, lincRNAs in pig skeletal muscles are largely undiscovered and their biological functions remain elusive. In this study, we assembled transcriptomes using RNA-seq data published in previous studies of our laboratory group and identified 323 lincRNAs in porcine leg muscle. We found that these lincRNAs have shorter transcript length, fewer exons and lower expression level than protein-coding genes. Gene ontology and pathway analyses indicated that many potential target genes (PTGs) of lincRNAs were involved in skeletal-muscle-related processes, such as muscle contraction and muscle system process. Combined our previous studies, we found a potential regulatory mechanism in which the promoter methylation of lincRNAs can negatively regulate lincRNA expression and then positively regulate PTG expression, which can finally result in abnormal phenotypes of cloned piglets through a certain unknown pathway. This work detailed a number of lincRNAs and their target genes involved in skeletal muscle growth and development and can facilitate future studies on their roles in skeletal muscle growth and development.

Quisinostat treatment improves histone acetylation and developmental competence of porcine somatic cell nuclear transfer embryos

Abnormal epigenetic modifications are considered a main contributing factor to low cloning efficiency. In the present study, we explored the effects of quisinostat, a novel histone deacetylase inhibitor, on blastocyst formation rate in porcine somatic-cell nuclear transfer (SCNT) embryos, on acetylation of histone H3 lysine 9 (AcH3K9), and on expression of POU5F1 protein and apoptosis-related genes BAX and BCL2. Our results showed that treatment with 10 nM quisinostat for 24 hr significantly improved the development of reconstructed embryos compared to the untreated group (19.0 ± 1.6% vs. 10.2 ± 0.9%; p < 0.05). Quisinostat-treated SCNT embryos also possessed significantly increased AcH3K9 at the pseudo-pronuclear stage (p < 0.05), as well as improved immunostaining intensity for POU5F1 at the blastocyst stage (p < 0.05). While no statistical difference in BAX expression was observed, BCL2 transcript abundance was significantly different in the quisinostat-treated compared to the untreated control group. Of the 457 quisinostat-treated cloned embryos transferred into three surrogates, six fetuses developed from the one sow that became pregnant. These findings suggested that quisinostat can regulate gene expression and epigenetic modification, facilitating nuclear reprogramming, and subsequently improving the developmental competence of pig SCNT embryos and blastocyst quality.