29 EFFECT OF EMBRYO CULTURE LENGTH ON PRODUCTION OF CLONED TRANSGENIC GOATS

The yield of blastocysts and hatched blastocysts using in vitro production (IVP) in goats are still low. The development of caprine embryos is frequently arrested at the 8- to 16-cell stage, indicating suboptimal culture conditions (Jimenez-Macedo et al. 2005 Theriogenology 64, 1249–1262). Our goal was to produce transgenic goats by somatic cell nuclear transfer (SCNT) and further determine whether the length of embryo culture has an effect on development to term. We compared the efficiency of transferring single-cell embryos 12 h post-activation to transferring 4- to 8-cell embryos cultured for 60 h post-activation. Nine transgenic goats from 2 cell lines were produced through SCNT. Somatic donor cells were obtained from 2 sources: adult fibroblasts and fetal fibroblasts. Adult fibroblasts were obtained from a transgenic doe skin biopsy. Fetal fibroblasts were isolated from a 25-day-old fetus and then electroporated with a pcDNA3.1DV5-MHC-TGF-β1cys33ser vector, followed by G418 selection, screening, and subsequent use for SCNT. Oocytes with >4 layers of cumulus cells were collected by slicing abattoir ovaries and matured in vitro for 21 to 23 h. After being denuded, oocytes presenting a first polar body were enucleated and received a donor cell from 1 of the 2 cell lines. Fused embryos were then activated for 5 min in 5 µM ionomycin, followed by 4 h in 2 mM DMAP with 5 µg of cycloheximide mL–1. Activated embryos were cultured in G1 medium with 5 mg of BSA mL–1 for either 12 or 60 h post-activation, followed by surgical transfer into the oviducts of recipients synchronized to show estrus within 12 h of SCNT. Overall, 376 embryos were transferred into 23 recipients. Pregnancy was examined by ultrasonography on Day 30 post-transfer. No pregnancy losses were observed after Day 30 of gestation. All kids were born live (42% of recipients receiving embryos cultured for 12 h gave birth, compared with only 9% when cultured for 60 h). The data (Table 1) suggest that a longer culture time in vitro significantly reduces viability of cloned embryos. Table 1.Twelve-hour versus 60-h embryo culture This work was supported by Utah Agricultural Experiment Station project no. 1100.

30 GENERATION OF CLONED TRANSGENIC GOATS WITH CARDIAC SPECIFIC OVEREXPRESSION OF TRANSFORMING GROWTH FACTOR β1

Transforming growth factor β1 (TGF-β1) has a potent profibrotic function and is central to signaling cascades involved in interstitial fibrosis, which plays a critical role in the pathobiology of cardiomyopathy and contributes to diastolic and systolic dysfunction. In addition, fibrotic remodeling is responsible for generation of re-entry circuits that promote arrhythmias (Bujak and Frangogiannis 2007 Cardiovasc. Res. 74, 184–195). Due to the small size of the heart, functional electrophysiology of transgenic mice is problematic. Large transgenic animal models have the potential to offer insights into conduction heterogeneity associated with fibrosis and the role of fibrosis in cardiovascular diseases. The goal of this study was to generate transgenic goats overexpressing an active form of TGFβ-1 under control of the cardiac-specific α-myosin heavy chain promoter (α-MHC). A pcDNA3.1DV5-MHC-TGF-β1cys33ser vector was constructed by subcloning the MHC-TGF-β1 fragment from the plasmid pUC-BM20-MHC-TGF-β1 (Nakajima et al. 2000 Circ. Res. 86, 571–579) into the pcDNA3.1D V5 vector. The Neon transfection system was used to electroporate primary goat fetal fibroblasts. After G418 selection and PCR screening, transgenic cells were used for SCNT. Oocytes were collected by slicing ovaries from an abattoir and matured in vitro in an incubator with 5% CO2 in air. Cumulus cells were removed at 21 to 23 h post-maturation. Oocytes were enucleated by aspirating the first polar body and nearby cytoplasm by micromanipulation in Hepes-buffered SOF medium with 10 µg of cytochalasin B mL–1. Transgenic somatic cells were individually inserted into the perivitelline space and fused with enucleated oocytes using double electrical pulses of 1.8 kV cm–1 (40 µs each). Reconstructed embryos were activated by ionomycin (5 min) and DMAP and cycloheximide (CHX) treatments. Cloned embryos were cultured in G1 medium for 12 to 60 h in vitro and then transferred into synchronized recipient females. Pregnancy was examined by ultrasonography on day 30 post-transfer. A total of 246 cloned embryos were transferred into 14 recipients that resulted in production of 7 kids. The pregnancy rate was higher in the group cultured for 12 h compared with those cultured 36 to 60 h [44.4% (n = 9) v. 20% (n = 5)]. The kidding rates per embryo transferred of these 2 groups were 3.8% (n = 156) and 1.1% (n = 90), respectively. The PCR results confirmed that all the clones were transgenic. Phenotype characterization [e.g. gene expression, electrocardiogram (ECG), and magnetic resonance imaging (MRI)] is underway. We demonstrated successful production of transgenic goat via SCNT. To our knowledge, this is the first transgenic goat model produced for cardiovascular research. This work was supported by the Utah Science Technology and Research Initiative, Utah Multidisciplinary Arrhythmia Consortium.

136 USE OF NANOFLUIDIC RT QUANTITATIVE POLYMERASE CHAIN REACTION TO STUDY VARIATION IN GENE EXPRESSION BETWEEN SINGLE BOVINE OOCYTE AND BLASTOCYST SAMPLES

Most research into gene expression of oocyte and pre-implantation-stage embryos has been on pooled samples. Little work has been done at the single oocyte or early embryo levels. Our hypothesis was that a large amount of variation exists in relative transcript abundance between individual oocytes/embryos, which may ultimately be associated with inherent developmental potential. Because most studies to date have been on pooled samples, only very limited data have been presented that explain whether such variation exists, or if most oocytes/embryos within a pool are similar in gene expression. To generate preliminary information about the amount of variation in gene expression that exists between single oocytes and blastocyst-stage embryos, 4 single oocyte and 8 single blastocyst samples were compared with pooled oocyte samples of 10 and 20 and a pooled blastocyst sample of 10. Oocyte maturation and embryo production were performed according to established protocols (see Aston et al. 2010 Cell Reprog.). The 24 genes selected for use in this analysis consisted mostly of pluripotency genes, imprinted genes and housekeeping genes. To analyse such small samples we used nanofluidic BioMark® quantitative PCR (qPCR) technology from Fluidigm (San Francisco, CA, USA). Complementary DNA was generated and preamplified by adding the samples listed above directly to a reverse-transcription/preamplification mix according to a prevalidated protocol from Fluidigm. Samples were run in duplicate on a single 48.48 microfluidic chip using intercalating dye qPCR technology. Each primer set was run in duplicate as well, resulting in 4 data points for each sample and primer set combination. Data were analysed using the relative standard curve method. We were able to produce preliminary data on how reproducible data generation is with this platform on single oocyte and blastocyst samples. Correlations between assay and sample replicates were high (R2 = 0.998 and R2 = 0.967, respectively). Among the oocyte samples, a fold change difference of 2 or more was found in 9 of the 24 primer sets. A similar analysis of the blastocyst samples yielded fold changes over 2 for 12 of the 24 primer sets. These preliminary data suggest that the use of nanofluidic qPCR technology may be useful for the study of gene expression variation among single oocyte and blastocyst samples. Funding was provided to S. C. Isom through the Utah Agricultural Experiment Station (program project #UTA00151).

246 EVIDENCE OF FOCAL ADHESION ASSEMBLY IN BOVINE OOCYTES

Integrins are located on the plasma membrane of bovine oocytes and have been implicated in bovine fertilization and activation (Campbell et al. 2000; Sessions et al. 2006). In response to signals from the extracellular matrix, activated integrins cluster at focal adhesions and interact with the cytoskeleton via signalling molecules, including focal adhesion kinase (FAK), α-actinin, phosphotyrosine, and talin. Immunohistochemistry was used to illustrate the formation of focal adhesions at the site of sperm binding in bovine oocytes during fertilization. To confirm antibody specificity, proteins were recovered from bovine oocyte lysate, separated by electrophoreses, and exposed to Western blotting. Specificity was confirmed based on antibody binding to the correctly sized bovine protein in the blot. Bovine oocytes were recovered, matured in vitro, and exposed to spermatozoa as described previously. Antibodies were then used to directly identify co-localization of FAK, α-actinin, phophotyrosine, and talin with each other in addition to localization with β-integrin isotypes within the bovine oocyte plasma membrane. Appropriate controls were performed in which all steps were duplicated with the elimination of the primary antibodies, to confirm that immunohistochemistry was specific for the proteins of interest. The results of immunohistochemistry indicate a co-localization of FAK protein clusters that involves specific oocyte membrane integrin proteins during fertilization. These findings illustrate the formation of focal adhesions via colocalization of signalling molecules with integrin β subunits in bovine oocytes and further support the hypothesis that induction of signalling pathways is initiated with sperm–oocyte binding in the bovine.

326 MICROINJECTIONS OF SMALL INTERFERING RNA AND COMPLEMENTARY RNA TO ELUCIDATE THE INVOLVEMENT OF ENDOGENOUS PHOSPHOLIPASE C ISOFORMS IN BOVINE OOCYTE ACTIVATION DURING FERTILIZATION

Phospholipase C (PLC) isoforms stimulate the hydrolysis of phosphatidyl inositol (4,5)-bisphosphate (PIP2) to produce diacylglycerol (DAG) and 1,4,5 inositol trisphosphate (IP3), with IP3 regulating the release of calcium (Ca2+) from the endoplasmic reticulum. This release of calcium is essential for oocyte activation, and a sperm-specific PLC isoform, PLCγ;, has been proposed as the primary agent that initiates the activation process. However, the oocyte contains many endogenous PLC isoforms (PLC β, γ, and δ) that could also be involved in regulating or initiating these calcium oscillations downstream of other initiating events. In order to better elucidate the involvement of endogenous PLC isoforms as well as the specific role of the sperm-specific form, small interfering RNA (siRNA) directed against the specific bovine PLC isoforms (PLCζ;, PLCγ1, PLCγ2, PLCδ1, PLCδ3, PLCδ4, PLCβ1, PLCβ3) were microinjected into bovine oocytes, and the subsequent effects on PLC mRNA levels and bovine fertilization were evaluated. Real-time PCR (qPCR) was used to quantify the levels of PLC message present in bovine oocytes at the time of injection (15 h post-maturation) and 6, 10, and 14 h post-injection. The qPCR results indicated a near-complete knockdown of mRNA levels in bovine oocytes 10 h post-injection for the isotypes PLCγ1, PLCγ2, PLCδ3, PLCδ4, PLCβ1, PLCβ3, but only partial knockdown of PLCS 1 mRNA. Oocytes microinjected with PLC siRNA were also fertilized and cultured in vitro according to our standard laboratory procedures (Reed et al. 1996 Theriogenology 45, 439-449). The oocytes microinjected with PLCζ;, PLCδ1, PLCδ3, PLCδ4, PLCβ1, PLCβ3 siRNA resulted in cleavage rates similar to the negative control siRNA, non-injected, and sham-injected treatment groups, whereas bovine oocytes microinjected with PLCγ1 and PLCγ2 siRNA had significantly lower cleavage rates compared with the controls. Additionally, complementary cRNA for each specific PLC isoform was microinjected into bovine oocytes to ascertain each isoform’s ability to induce parthenogenetic activation. Development was observed in oocytes microinjected with a variety of cRNAs, and the activating effects of the cRNA were negligible if the oocytes were microinjected with the corresponding siRNA before microinjection with cRNA. Interestingly, siRNA specific for PLCζ; failed to reduce cleavage when treated bovine oocytes were fertilized. These data illustrate the potential involvement of multiple endogenous PLC isoforms and not just the sperm-specific PLCζ; isoform in bovine oocyte activation during fertilization.

Effect of the time interval between fusion and activation on nuclear state and development in vitro and in vivo of bovine somatic cell nuclear transfer embryos

This study indicated that prolonged exposure of donor cell nuclei to oocyte cytoplasm before activation results in abnormal chromatin morphology, and reduced development to compacted morula/blastocyst stage in vitro. However, after transfer of embryos to recipients, there was no difference in pregnancy rates throughout gestation. Chromatin morphology was evaluated for embryos held 2, 3, 4 and 5 h between fusion and activation. In embryos held 2 h, 15/17 (88.2%) embryos contained condensed chromosomes, while only 12/24 (50.0%) embryos held 3 h exhibited this characteristic. The proportion of embryos with elongated or fragmented chromosomes tended to increase with increased hold time. While 15/19 (78.9%) of embryos held 2 h developed a single pronucleus 6 h after activation, only 8/22 (36.4%) had one pronucleus after a 4-h hold. Embryos held 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 h cleaved at rates of 207/281 (73.7%), 142/166 (85.5%), 655/912 (71.8%), 212/368 (57.6%), 406/667 (60.9%), 362/644 (56.2%) and 120/228 (52.6%) respectively. Further development to compacted morula/blastocyst stage occurred at rates of 78/281 (27.8%), 42/166 (25.3%), 264/912 (28.9%), 79/368 (21.5%), 99/667 (14.8%), 94/644 (14.6%) and 27/228 (11.8%) respectively. Embryos held less than 2.5 h between fusion and activation established pregnancies in 18/66 (27.3%) of recipients, while embryos held over 2.5 h established pregnancies at a rate of 17/57 (29.8%). This study indicates that holding bovine nuclear transfer embryos less than 2.5 h between fusion and activation results in improved nuclear morphology and increased development to compacted morula/blastocyst stage, and results in pregnancy rates equivalent to embryos held over 2.5 h.

Effects of amino acid substitutions in and around the arginine-glycine-aspartic acid (RGD) sequence on fertilization and parthenogenetic development in mature bovine oocytes

Integrins have been shown to be involved in the process of fertilization and many integrin-ligand interactions are mediated through the recognition of an arginine-glycine-aspartic acid (RGD) sequence. Despite the fact the RGD domain is a principal player in determining the functional characteristics of an adhesive protein, increasing evidence has accumulated implicating the amino acids flanking the RGD sequence in determining the functional properties of the RGD-containing protein. A set of linear peptides in which the amino acid sequence in and around the RGD tri-peptide was modified was synthesized to better understand the specificity of the RGD-receptor interaction. Mature oocytes were fertilized in vitro in the presence of RGD-containing and RGD-modified peptides. Both the RGD-containing and RGD-modified peptides impaired the ability of sperm to fertilize bovine oocytes, illustrated by a reduction in cleavage. The linear modified RGD containing peptides were also examined for their ability to induce parthenogenetic development with the objective of providing a linear RGD peptide with greater biological activity than the one (GRGDSPK) used previously (Campbell et al., 2000). The data demonstrate the specificity of the receptor for the RGD sequence, further implicate the involvement of integrins in the process of bovine fertilization, and illustrate the importance of the amino acids surrounding the RGD sequence in determining the binding and functional properties of RGD-containing peptides. The data support the findings that a linear RGD peptide can block fertilization and that amino acids around the RGD sequence have an impact on the biological activity of the receptor.