Aberrant levels of DNA methylation and H3K9 acetylation in the testicular cells of crossbred cattle-yak showing infertility

Although the interspecies hybridization of bovids, such as cattle-yak (Bos taurus × Bos grunniens), has heterosis benefits, the infertility of hybrid males affects the maintenance of dominant traits in subsequent generations. To achieve reproductive capacity, male germ cell development requires coordinated changes in gene expression, including DNA methylation and generalized histone modifications. Although gene expression-related mechanisms underlying hybrid male sterility have been investigated recently, information on the cell types and stage-specific controls remains limited. Here, we used immunohistochemistry and image analyses to evaluate the 5-methylcytosine (5MC) and acetyl-histone H3 Lys9 (AcK9) expression in all spermatogonia and testicular somatic cell types to determine their roles in cattle-yak spermatogenesis. Testicular tissues from yak (1-3 years old) and backcrossed hybrids (2 years old) were used. In yak, the AcK9 expression levels increased in all cell types during maturation, but the 5MC expression levels did not change until reaching 3 years when they increased in all testicular cell types, except spermatogonia. Cattle-yak hybrids showed higher 5MC expression levels and different AcK9 expression levels in all cell types compared to the same-aged yak. These results suggested that both gene modulation by AcK9 and constant levels of DNA methylation are required for spermatogenesis during maturation in yak. Therefore, inappropriate expression levels of both AcK9 and DNA methylation might be the major factors for disruption of normal germ cell development in cattle-yak. Additionally, various modulations occurred depending on the cell type. Further experiments are needed to identify the stage-specific gene expression modulations in each cell type in yak and cattle-yak to potentially solve the infertility issue in crossbreeding.

Genome-wide association study on milk production and somatic cell score for Thai dairy cattle using weighted single-step approach with random regression test-day model

Genome-wide association studies are a powerful tool to identify genomic regions and variants associated with phenotypes. However, only limited mutual confirmation from different studies is available. The objectives of this study were to identify genomic regions as well as genes and pathways associated with the first-lactation milk, fat, protein, and total solid yields; fat, protein, and total solid percentage; and somatic cell score (SCS) in a Thai dairy cattle population. Effects of SNPs were estimated by a weighted single-step GWAS, which back-solved the genomic breeding values predicted using single-step genomic BLUP (ssGBLUP) fitting a single-trait random regression test-day model. Genomic regions that explained at least 0.5% of the total genetic variance were selected for further analyses of candidate genes. Despite the small number of genotyped animals, genomic predictions led to an improvement in the accuracy over the traditional BLUP. Genomic predictions using weighted ssGBLUP were slightly better than the ssGBLUP. The genomic regions associated with milk production traits contained 210 candidate genes on 19 chromosomes [Bos taurus autosome (BTA) 1 to 7, 9, 11 to 16, 20 to 21, 26 to 27 and 29], whereas 21 candidate genes on 3 chromosomes (BTA 11, 16, and 21) were associated with SCS. Many genomic regions explained a small fraction of the genetic variance, indicating polygenic inheritance of the studied traits. Several candidate genes coincided with previous reports for milk production traits in Holstein cattle, especially a large region of genes on BTA14. We identified 141 and 5 novel genes related to milk production and SCS, respectively. These novel genes were also found to be functionally related to heat tolerance (e.g., SLC45A2, IRAG1, and LOC101902172), longevity (e.g., SYT10 and LOC101903327), and fertility (e.g., PAG1). These findings may be attributed to indirect selection in our population. Identified biological networks including intracellular cell transportation and protein catabolism implicate milk production, whereas the immunological pathways such as lymphocyte activation are closely related to SCS. Further studies are required to validate our findings before exploiting them in genomic selection.

Molecular signature and colony morphology affect in vitro pluripotency of porcine induced pluripotent stem cells

Overall efficiency of cell reprogramming for porcine fibroblasts into induced pluripotent stem cells (iPSCs) is currently poor, and few cell lines have been established. This study examined gene expression during early phase of cellular reprogramming in the relationship to the iPSC colony morphology and in vitro pluripotent characteristics. Fibroblasts were reprogrammed with OCT4, SOX2, KLF4 and c-MYC. Two different colony morphologies referred to either compact (n = 10) or loose (n = 10) colonies were further examined for proliferative activity, gene expression and in vitro pluripotency. A total of 1,697 iPSC-like colonies (2.34%) were observed after gene transduction. The compact colonies contained with tightly packed cells with a distinct-clear border between the colony and feeder cells, while loose colonies demonstrated irregular colony boundary. For quantitative expression of genes responsible for early phase cell reprogramming, the Dppa2 and EpCAM were significantly upregulated while NR0B1 was downregulated in compact colonies compared with loose phenotype (p < .05). Higher proportion of compact iPSC phenotype (5 of 10, 50%) could be maintained in undifferentiated state for more than 50 passages compared unfavourably with loose morphology (3 of 10, 30%). All iPS cell lines obtained from these two types of colony morphologies expressed pluripotent genes and proteins (OCT4, NANOG and E-cadherin). In addition, they could aggregate and form three-dimensional structure of embryoid bodies. However, only compact iPSC colonies differentiated into three germ layers. Molecular signature of early phase of cell reprogramming coupled with primary colony morphology reflected the in vitro pluripotency of porcine iPSCs. These findings can be simply applied for pre-screening selection of the porcine iPSC cell line.

Rabbit induced pluripotent stem cells retain capability of in vitro cardiac differentiation

Stem cells are promising cell source for treatment of multiple diseases as well as myocardial infarction. Rabbit model has essentially used for cardiovascular diseases and regeneration but information on establishment of induced pluripotent stem cells (iPSCs) and differentiation potential is fairly limited. In addition, there is no report of cardiac differentiation from iPSCs in the rabbit model. In this study, we generated rabbit iPSCs by reprogramming rabbit fibroblasts using the 4 transcription factors (OCT3/4, SOX2, KLF4, and c-Myc). Three iPSC lines were established. The iPSCs from all cell lines expressed genes (OCT3/4, SOX2, KLF4 and NANOG) and proteins (alkaline phosphatase, OCT-3/4 and SSEA-4) essentially described for pluripotency (in vivo and in vitro differentiation). Furthermore, they also had ability to form embryoid body (EB) resulting in three-germ layer differentiation. However, ability of particular cell lines and cell numbers at seeding markedly influenced on EB formation and also their diameters. The cell density at 20,000 cells per EB was selected for cardiac differentiation. After plating, the EBs attached and cardiac-like beating areas were seen as soon as 11 days of culture. The differentiated cells expressed cardiac progenitor marker FLK1 (51 ± 1.48%) on day 5 and cardiac troponin-T protein (10.29 ± 1.37%) on day 14. Other cardiac marker genes (cardiac ryanodine receptors (RYR2), α-actinin and PECAM1) were also expressed. This study concluded that rabbit iPSCs remained their in vitro pluripotency with capability of differentiation into mature-phenotype cardiomyocytes. However, the efficiency of cardiac differentiation is still restricted.

Generation of porcine induced-pluripotent stem cells from Sertoli cells

Induced pluripotent stem cells (iPSCs) are generated by reprogramming of somatic cells using four transcription factors: OCT4, SOX2, KLF-4, and c-MYC (OSKM). However, reprogramming efficiency of iPSCs is currently poor. In this study, we used the Sertoli line as a novel cell source for somatic cell reprogramming. Neonatal testes were collected from 1-week-old piglets. The testes were digested by a two-step enzymatic method to isolate Sertoli cells. The latter were transfected with retroviral vectors expressing OSKM. The Sertoli iPSC-like colonies were subjected to morphological analysis, alkaline phosphatase staining, RT-PCR, G-banding karyotyping, in vitro differentiation, and in vivo differentiation. Primary Sertoli cells had polygon-shaped morphology and manifested phagocytic activity as determined by a fluorescent bead assay. Sertoli cells also expressed the anti-Müllerian hormone protein in the cytoplasm. According to RT-PCR results, these cells expressed Sertoli cell markers (FSHR, KRT18, and GATA6) and endogenous transcription factors genes (KLF4 and c-MYC). A total of 240 colonies (0.3% efficiency) were detected by day 7 after viral transduction of 72500 cells. The Sertoli iPSC-like colonies contained small cells with a high nucleus-to-cytoplasm ratio. These colonies tested positive for alkaline phosphatase staining, expressed endogenous pluripotency genes, and had a normal karyotype. All these cell lines could form in vitro three-dimensional aggregates that represented three germ layers of embryonic-like cells. A total of two cell lines used for in vivo differentiation produced high-efficiency teratoma. In conclusion, Sertoli cells can efficiently serve as a novel cell source for iPSC reprogramming.

186 Improving Success Rate of Establishment and Maintenance of Porcine Induced Pluripotent Stem Cells by Investigation of Colony Morphology

Induced pluripotent stem cells (iPS cells) are generated by reprogramming of somatic cells using ectopic introduction of 4 transcription factors, including OCT4, SOX2, KLF4, and c-MYC (OSKM). Fibroblast cells are the most commonly used as a primary cell source for iPS cells because they are easy to harvest and culture. However, reprogramming efficiency of porcine fibroblasts is poor (~0.1%). During reprogramming process, mixed populations of primary colonies become the major obstacle in iPS establishment. In this study, we characterised 2 different colony morphologies at colony pick-up (compact and loose iPS morphology). We hypothesised that compact colonies will proceed to long-term culture and pluripotency. The fibroblast cells were isolated from tails of piglets and transfected with retroviral vectors expressing OSKM. The primary colonies were counted on Day 7 after gene transduction. The iPS-like colonies were divided into compact (n = 10) and loose (n = 10) morphology at colony pick-up. The characteristics of iPS-like cell lines were analysed by morphology, alkaline phosphatase staining, G-banding karyotype, immunofluorescence staining (OCT4), pluripotent gene expression (RT-PCR), and embryoid body formation. A total of 1,697 iPS-like colonies (2.34%) were observed. The compact colonies contained with tightly packed cells with distinct border between iPS colony and feeder cells, while colonies with irregular shape and border were classified as loose colonies. These 2 types of iPS-like colonies expressed alkaline phosphatase and OCT4. A total 5 of 10 (50%) compact morphology cell lines could be maintained in the undifferentiated state for more than 50 passages. But only 3 of 10 (30%) loose morphology cell lines demonstrated pluripotent characteristics. G-Banding karyotype analysis revealed normal chromosome number (n = 38). All of the cell lines also expressed endogenous pluripotent genes, including OSKM and NANOG and formed three-dimensional aggregating masses. In this study, we found that the cell lines from compact morphology could be maintained for longer than those of the loose morphology. A high rate of differentiation of loose iPS colony may also indicate that this type of colony has different pluripotency signals or incomplete reprogramming compared with compact colony. In conclusion, selection of compact colony morphology at colony pick-up is simple and reflects long-term propagation of porcine iPS cell lines. This information is important for improving the success rate of establishment and maintenance of porcine iPS cells.

184 Establishment of Porcine Induced Pluripotent Stem Cell Lines by Adding LIN 28 Transcription Factor

The establishment of porcine induced pluripotent stem cells (piPSC) is important in the field of human biomedical regenerative medicine. The pig model is a more representative model than current rodent models because it better mimics human physiology in different organ systems. The piPSC can be traditionally generated by reprogramming somatic cells using 4 transcription factors (4TF: OCT4, SOX2, KLF4, and c-MYC), similarly in human. However, it is difficult to maintain the pluripotent state of reprogrammed cells and they exhibit poor differentiation capacity. Hence, the 4TF may be not enough to reprogram porcine somatic cells. This study aimed to establish piPSC by adding LIN28 (referred to as 5TF) to the traditional 4TF, via retroviral vector. Here, we report the successful establishment of 3 piPSC lines by using the 5TF. All 5TF-piPSC lines exhibited a normal karyotype (38, XY) and a typical mouse embryonic stem cell (ESC) morphology, including tightly packed and dome-like shape, even after they were propagated over 40 passages. All 5TF-piPSC lines were positive for alkaline phosphatase staining and expressed high levels of ESC-like markers (OCT4, SOX2, NANOG, and SSEA-1). Importantly, the 5TF-piPSC lines showed pluripotent capacity, as evidenced by differentiation into 3 germ layers in vitro following cystic embryoid body formation, as well as by efficiently forming teratomas containing all 3 embryonic germ layers in vivo. Moreover, the 5TF-piPSC lines showed spontaneously contractile cardiomyocytes and expressed cardiomyocyte markers (cardiac troponin T) during spontaneous cardiac differentiation using cell aggregation into spherical-like structures referred to as embryoid bodies. Thus, the addition of LIN28 TF promoted long-term pluripotency of piPSC and enhanced the ability to differentiate towards 3 embryonic germ layers and cardiac lineage. This research project is supported by grants from the Mahidol University, Thailand.

341 FELINE EMBRYONIC STEM-LIKE CELLS DERIVED FROM IN VITRO-PRODUCED BLASTOCYSTS RETAIN IN VITRO DIFFERENTIATION POTENTIAL

Embryonic stem (ES) cells are pluripotent cells that can differentiate into all 3 germ layers, including endoderm, mesoderm, and ectoderm. Embryonic stem cells are generally divided into 2 types, naïve and primed-state, depending on their signaling pathways. Domestic cat is a useful animal model for the study of human diseases because many genetic and infectious diseases in the cat are analogous with similar aetiology to human diseases. The cat can also be used as a research model for reproductive physiology and conservation of wild felids. Until recently, information on establishment of feline ES cells is limited. The objectives of this study were to isolate cat ES cells from in vitro-produced blastocysts and to examine the effect of different concentrations of basic fibroblast growth factor (bFGF) on the expression of pluripotent genes. Inner cell masses (ICM) from cat blastocysts (n = 40, Day 7 after in vitro fertilization) that were matured, fertilized, and cultured entirely in vitro, were isolated by immunosurgery and plated on mitmycin-treated mouse embryonic fibroblasts. The ICM (n = 20) were then cultured in embryonic stem cell medium containing 1000 IU mL–1 of leukemia inhibitory factor (LIF) and different bFGF concentrations (0, 4, 10, and 20 ng mL–1). The ICM outgrowths at 7 days postplating were collected and analysed for expression of pluripotent genes (SOX-2, OCT-4, and NANOG). Results showed that transcription levels of all 3 pluripotent genes were higher in ICM outgrowths cultured in 20 ng mL–1 of bFGF compared with the lower concentrations. For isolation of ES cells, ICM (n = 20) were cultured in embryonic stem cell medium supplemented with 1000 IU mL–1 of LIF and 20 ng mL–1 of bFGF due to the results obtained from the above experiment. Established ES cells were characterised by detecting alkaline phosphatase (AP) activity and expression of ES markers (SOX-2, OCT-4, SSEA-4) at protein level, and karyotyped at passage 20 and 40. In vitro differentiation into embryoid bodies (EB) was induced by the hanging drop technique, and EB samples (n = 5 for each time point) were tested for the expression of TTR, AFP, T (Bracyury), NKX2.5, MAP-2, and NESTIN genes at 0, 7, and 14 days of culture. A total of 3 ES-like cell lines were established with a typical ES morphology, such as a well-defined colony, a large nucleus to cytoplasm ratio with 1 to 2 prominent nucleoli. The 3 ES-like cell lines were passaged up to 40 times with a normal diploid karyotype (n = 38). They were strongly positive for AP, SOX-2, OCT-4, and SSEA-4. Following EB culture, cell aggregation and cystic-like structure were observed. The EB samples also expressed all differentiation markers. This study reports that feline ES-like cell lines can be generated from in vitro-produced feline blastocysts. The ES cell lines can be repeatedly passaged indicating self-renewal ability, and gene expression of the EB demonstrates cellular differentiation into all 3 germ layers.