Diagnosis and severity criteria for sinusoidal obstruction syndrome/veno-occlusive disease in pediatric patients: a new classification from the European society for blood and marrow transplantation

The advances in hematopoietic cell transplantation (HCT) over the last decade have led to a transplant-related mortality below 15%. Hepatic sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD) is a life-threatening complication of HCT that belongs to a group of diseases increasingly identified as transplant-related, systemic endothelial diseases. In most cases, SOS/VOD resolves within weeks; however, severe SOS/VOD results in multi-organ dysfunction/failure with a mortality rate >80%. A timely diagnosis of SOS/VOD is of critical importance, given the availability of therapeutic options with favorable tolerability. Current diagnostic criteria are used for adults and children. However, over the last decade it has become clear that SOS/VOD is significantly different between the age groups in terms of incidence, genetic predisposition, clinical presentation, prevention, treatment and outcome. Improved understanding of SOS/VOD and the availability of effective treatment questions the use of the Baltimore and Seattle criteria for diagnosing SOS/VOD in children. The aim of this position paper is to propose new diagnostic and severity criteria for SOS/VOD in children on behalf of the European Society for Blood and Marrow Transplantation.

Stage-dependent remodeling of the nuclear envelope and lamina during rabbit early embryonic development

Utilizing 3D structured illumination microscopy, we investigated the quality and quantity of nuclear invaginations and the distribution of nuclear pores during rabbit early embryonic development and identified the exact time point of nucleoporin 153 (NUP153) association with chromatin during mitosis. Contrary to bovine early embryonic nuclei, featuring almost exclusively nuclear invaginations containing a small volume of cytoplasm, nuclei in rabbit early embryonic stages show additionally numerous invaginations containing a large volume of cytoplasm. Small-volume invaginations frequently emanated from large-volume nuclear invaginations but not vice versa, indicating a different underlying mechanism. Large- and small-volume nuclear envelope invaginations required the presence of chromatin, as they were restricted to chromatin-positive areas. The chromatin-free contact areas between nucleolar precursor bodies (NPBs) and large-volume invaginations were free of nuclear pores. Small-volume invaginations were not in contact with NPBs. The number of invaginations and isolated intranuclear vesicles per nucleus peaked at the 4-cell stage. At this stage, the nuclear surface showed highly concentrated clusters of nuclear pores surrounded by areas free of nuclear pores. Isolated intranuclear lamina vesicles were usually NUP153 negative. Cytoplasmic, randomly distributed NUP153-positive clusters were highly abundant at the zygote stage and decreased in number until they were almost absent at the 8-cell stage and later. These large NUP153 clusters may represent a maternally provided NUP153 deposit, but they were not visible as clusters during mitosis. Major genome activation at the 8- to 16-cell stage may mark the switch from a necessity for a deposit to on-demand production. NUP153 association with chromatin is initiated during metaphase before the initiation of the regeneration of the lamina. To our knowledge, the present study demonstrates for the first time major remodeling of the nuclear envelope and its underlying lamina during rabbit preimplantation development.

3D structured illumination microscopy of mammalian embryos and spermatozoa

Background

Super-resolution fluorescence microscopy performed via 3D structured illumination microscopy (3D-SIM) is well established on flat, adherent cells. However, blastomeres of mammalian embryos are non-adherent, round and large. Scanning whole mount mammalian embryos with 3D-SIM is prone to failure due to the movement during scanning and the large distance to the cover glass.

Results

Here we present a highly detailed protocol that allows performing 3D-SIM on blastomeres of mammalian embryos with an image quality comparable to scans in adherent cells. This protocol was successfully tested on mouse, rabbit and cattle embryos and on rabbit spermatozoa.

Conclusions

Our protocol provides detailed instructions on embryo staining, blastomere isolation, blastomere attachment, embedding, correct oil predictions, scanning conditions, and oil correction choices after the first scan. Finally, the most common problems are documented and solutions are suggested. To our knowledge, this protocol presents for the first time a highly detailed and practical way to perform 3D-SIM on mammalian embryos and spermatozoa.

Positional changes of a pluripotency marker gene during structural reorganization of fibroblast nuclei in cloned early bovine embryos

Cloned bovine preimplantation embryos were generated by somatic cell nuclear transfer (SCNT) of bovine fetal fibroblasts with a silent copy of the pluripotency reporter gene GOF, integrated at a single site of a chromosome 13. GOF combines the regulatory Oct4/Pou5f1 sequence with the coding sequence for EGFP. EGFP expression served as a marker for pluripotency gene activation and was consistently detected in preimplantation embryos with 9 and more cells. Three-dimensional radial nuclear positions of GOF, its carrier chromosome territory and non-carrier homolog were measured in nuclei of fibroblasts, and of day 2 and day 4 embryos, carrying 2 to 9 and 15 to 22 cells, respectively. We tested, whether transcriptional activation was correlated with repositioning of GOF toward the nuclear interior either with a corresponding movement of its carrier chromosome territory 13 or via the formation of a giant chromatin loop. A significant shift of GOF away from the nuclear periphery was observed in day 2 embryos together with both carrier and non-carrier chromosome territories. At day 4, GOF, its carrier chromosome territory 13 and the non-carrier homolog had moved back toward the nuclear periphery. Similar movements of both chromosome territories ruled out a specific GOF effect. Pluripotency gene activation was preceded by a transient, radial shift of GOF toward the nuclear interior. The persistent co-localization of GOF with its carrier chromosome territory rules out the formation of a giant chromatin loop during GOF activation.

Reprogramming of fibroblast nuclei in cloned bovine embryos involves major structural remodeling with both striking similarities and differences to nuclear phenotypes of in vitro fertilized embryos

Nuclear landscapes were studied during preimplantation development of bovine embryos, generated either by in vitro fertilization (IVF), or generated as cloned embryos by somatic cell nuclear transfer (SCNT) of bovine fetal fibroblasts, using 3-dimensional confocal laser scanning microscopy (3D-CLSM) and structured illumination microscopy (3D-SIM). Nuclear landscapes of IVF and SCNT embryonic nuclei were compared with each other and with fibroblast nuclei. We demonstrate that reprogramming of fibroblast nuclei in cloned embryos requires changes of their landscapes similar to nuclei of IVF embryos. On the way toward the 8-cell stage, where major genome activation occurs, a major lacuna, enriched with splicing factors, was formed in the nuclear interior and chromosome territories (CTs) were shifted toward the nuclear periphery. During further development the major lacuna disappeared and CTs were redistributed throughout the nuclear interior forming a contiguous higher order chromatin network. At all stages of development CTs of IVF and SCNT embryonic nuclei were built up from chromatin domain clusters (CDCs) pervaded by interchromatin compartment (IC) channels. Quantitative analyses revealed a highly significant enrichment of RNA polymerase II and H3K4me3, a marker for transcriptionally competent chromatin, at the periphery of CDCs. In contrast, H3K9me3, a marker for silent chromatin, was enriched in the more compacted interior of CDCs. Despite these striking similarities, we also detected major differences between nuclear landscapes of IVF and cloned embryos. Possible implications of these differences for the developmental potential of cloned animals remain to be investigated. We present a model, which integrates generally applicable structural and functional features of the nuclear landscape.

Ultra-Structural Alterations in In Vitro Produced Four-Cell Bovine Embryos Following Controlled Slow Freezing or Vitrification

Cryopreservation is the process of freezing and preserving cells and tissues at low temperatures. Controlled slow freezing and vitrification have successfully been used for cryopreservation of mammalian embryos. We investigated the effect of these two cryopreservation methods on in vitro produced four-cell stage bovine embryos which were classified according to their quality and separated into three groups. The first group was maintained as untreated controls (n = 350). Embryos of the second (n = 385) and the third (n = 385) groups were cryopreserved either by controlled slow freezing or by vitrification. Embryos in groups 2 and 3 were thawed after 1 day. Hundred embryos were randomly selected from the control group, and 100 morphologically intact embryos from the second and third group were thawed after 1 day and cultured to observe the development up to the blastocyst stage. The blastocyst development rate was 22% in the control group, 1% in the slow-freezing group and 3% in the vitrification group. Remaining embryos of all three groups were examined by light microscopy, transmission electron microscopy and immunofluorescence confocal microscopy with subsequent histological staining procedures. Cryopreservation caused degenerative changes at the ultra-structural level. Compared with vitrification, slow freezing caused an increased mitochondrial degeneration, cytoplasmic vacuolization, disruption of the nuclear and plasma membrane integrity, organelle disintegration, cytoskeletal damage, a reduced thickness of the zona pellucida and a formation of fractures in the zona pellucida. Further studies are required to understand and decrease the harmful effects of cryopreservation.

Remodeling of the Nuclear Envelope and Lamina during Bovine Preimplantation Development and Its Functional Implications

The present study demonstrates a major remodeling of the nuclear envelope and its underlying lamina during bovine preimplantation development. Up to the onset of major embryonic genome activation (MGA) at the 8-cell stage nuclei showed a non-uniform distribution of nuclear pore complexes (NPCs). NPCs were exclusively present at sites where DNA contacted the nuclear lamina. Extended regions of the lamina, which were not contacted by DNA, lacked NPCs. In post-MGA nuclei the whole lamina was contacted rather uniformly by DNA. Accordingly, NPCs became uniformly distributed throughout the entire nuclear envelope. These findings shed new light on the conditions which control the integration of NPCs into the nuclear envelope. The switch from maternal to embryonic production of mRNAs was accompanied by multiple invaginations covered with NPCs, which may serve the increased demands of mRNA export and protein import. Other invaginations, as well as interior nuclear segments and vesicles without contact to the nuclear envelope, were exclusively positive for lamin B. Since the abundance of these invaginations and vesicles increased in concert with a massive nuclear volume reduction, we suggest that they reflect a mechanism for fitting the nuclear envelope and its lamina to a shrinking nuclear size during bovine preimplantation development. In addition, a deposit of extranuclear clusters of NUP153 (a marker for NPCs) without associated lamin B was frequently observed from the zygote stage up to MGA. Corresponding RNA-Seq data revealed deposits of spliced, maternally provided NUP153 mRNA and little unspliced, newly synthesized RNA prior to MGA, which increased strongly at the initiation of embryonic expression of NUP153 at MGA.

82 STRUCTURAL REMODELLING OF THE NUCLEAR ENVELOPE IN BOVINE PRE-IMPLANTATION EMBRYOS

In the present study, we investigated the changes of the nuclear envelope and its underlying lamina, as well as features of higher order chromatin organisation in bovine embryos generated by in vitro fertilization during pre-implantation development. We used super-resolution, 3-dimensional structured illumination microscopy combined with 2-colour immunostaining of the nucleoporin Nup153 and lamin B serving as markers for nuclear pore complexes (NPC) and the nuclear lamina, respectively. DNA was counterstained with 4′,6-diamidino-2-phenylindole (DAPI). We examined 20 nuclei for the zygote (10 male pronuclei and 10 female pronuclei; n = 10) and the blastocyst (10 trophectoderm and 10 inner cell mass nuclei; n = 1) stage, and 10 nuclei for each the 2-cell (n = 5), 4-cell (n = 3), 8-cell (n = 2), 19-cell (n = 1), and morula (n = 1) stages. We report 4 major findings: (1) At the onset of major genome activation (MGA) nuclei showed a peripheral location of chromosome territories (CT), separated by wide IC channels and surrounding a major lacuna depleted of chromatin. The NPC were exclusively present at sites where DAPI-stained DNA contacted the nuclear lamina, whereas extended lamina regions without such contacts lacked NPC. In post-MGA nuclei, the CT formed a higher order chromatin network distributed throughout the entire nuclear space and the major lacuna disappeared. In line with a switch to a ubiquitous lining of DNA at the lamina, NPC were also uniformly distributed throughout the entire nuclear envelope. These findings shed new light on the conditions that control the integration of NPC into the nuclear envelope. (2) The switch from maternal to embryonic production of mRNA was accompanied by an increased amount of nuclear lamina invaginations covered with NPC, which may serve the increased demands of mRNA export and protein import. (3) Other invaginations, as well as interior nuclear segments and vesicles without contact to the nuclear envelope, were exclusively positive for lamin B. Because an increase in these lamin B positive structures occurred in concert with a massive nuclear volume reduction, we suggest that they reflect a mechanism for fitting the nuclear envelope and its lamina to a shrinking nuclear size throughout bovine pre-implantation development. (4) Throughout the cytoplasm, randomly distributed extranuclear clusters of Nup153 without associated lamin B were frequently observed from the zygote stage up to MGA. These clusters may represent a deposit of maternal Nup153 and likely other nucleoporines not studied here. Corresponding RNA-Seq data revealed deposits of spliced, maternally provided NUP153 mRNA and little unspliced RNA before MGA, which increased strongly at the initiation of embryonic NUP153 expression at MGA. After MGA, these clusters were exclusively located at or near the nuclear border and were no longer present at the morula stage and later. In conclusion, our findings demonstrate the dynamic adaptation of the nuclear envelope to the special needs of bovine pre-implantation development and show the necessity of chromatin association for the integration of nuclear pores into the nuclear envelope.

92 NUCLEAR INVAGINATIONS ADAPT TO RABBIT EARLY EMBRYONIC DEVELOPMENT

Nuclear invaginations carrying nuclear pores may facilitate increased mRNA export and protein import to areas inside the nucleus remote from the nuclear border. In this study on rabbit embryos, we investigated whether large early embryonic nuclei and the increased import/export demands around major embryonic genome activation (MGA) at the 8-cell stage affected the quantity of nuclear invaginations carrying nuclear pores. To achieve this objective, we used super-resolution 3-dimensional structured illumination microscopy on 10 pronuclei or nuclei per stage of 23 in vivo-fertilized and in vitro-cultured embryos stained with antibodies for the nucleoporin NUP153 and lamin B and stained with 4′,6-diamidino-2-phenylindole (DAPI) for chromatin. Statistical comparisons between stages were performed using the Wilcoxon rank-sum test. At the zygote stage, the female pronucleus displayed on average 16.5 and the male pronucleus featured on average 15.25 wide and narrow nuclear envelope invaginations, carrying large or tiny amounts of cytoplasm. Subsequent stages showed predominantly wide invaginations targeting nucleoli. The contact areas between nucleoli and invaginations were free of nuclear pores. In contrast, narrow invaginations, which are the almost exclusive type of invaginations during cattle and mouse pre-implantation development, were not in contact with nucleoli. At the 2-cell stage, the number of invaginations increased to an average of 27.3 invaginations per nucleus (P < 0.05) and increased again to peak at the 4-cell stage with 51.2 invaginations per nucleus (P < 0.01). At the 8-cell stage (MGA), the amount of nuclear invaginations was reduced to 25.4 invaginations per nucleus (P < 0.01). The reduced number of nuclear invaginations at the 8-cell stage could be associated with a significant decrease in average nuclear volume from 2593 µm3 at the 4-cell stage to 960 µm3 at the 8-cell stage (P < 0.001) and a subsequent reduced average distance from areas inside the nucleus to the nuclear border. Nuclear invagination numbers continued their decline at the 21-cell stage with 5.2 invaginations per nucleus (P < 0.001), whereas nuclear volumes decreased to 618 µm3 (P < 0.001). The morula stage, with 6.9 invaginations per nucleus (P = 0.9), and the blastocyst stage, with 4.5 invaginations per nucleus (P = 0.5), showed no more significant changes. Large NUP153 cytoplasmic clusters present before MGA may represent a maternally provided NUP153 deposit. MGA may mark the switch from the use of a NUP153 deposit to on-demand production. Additionally, over- and under-representation analyses on mitotic blastomeres revealed that NUP153 association with chromatin is initiated during metaphase before the initiation of the regeneration of the lamina (P < 0.001; chi-squared goodness-of-fit test). In conclusion, rabbit embryonic development is accompanied by stage-dependent changes of the amount of nuclear invaginations carrying nuclear pores. Although cattle and mouse embryos almost exclusively feature narrow invaginations restricted to the nuclear periphery and not in contact with nucleoli, rabbit embryos feature additional wide invaginations that can reach across the nucleus and target nucleoli.

67 CORRELATION OF ARCHITECTURAL AND FUNCTIONAL REPROGRAMMING OF NUCLEI DURING EMBRYONIC GENOME ACTIVATION OF EARLY BOVINE EMBRYOS GENERATED BY IVF AND SCNT

Development of mammalian pre-implantation embryos provides an excellent model to explore interactions of nuclear organisation and nuclear functions. Based on light optical sectioning with confocal laser scanning microscopy and structured illumination microscopy, we performed a quantitative three-dimensional image analysis of nuclei in early bovine embryos generated by in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT) of bovine fibroblast nuclei. The same sequence of changes was observed in nuclei of both IVF and SCNT embryos during embryonic genome activation (EGA) is that typically achieved in embryos between 8 and 16 cells. In both pre-EGA IVF and SCNT embryos, chromosome territories (CT) were assembled as spatially distinct entities at the nuclear periphery, whereas the nuclear interior was typically occupied by a mostly chromatin free lacuna enriched with splicing factors. Detection of H3K4m3 demonstrates the presence of transcriptionally competent chromatin before EGA, which was correlated with large-scale movements of CT into the nuclear interior and a several-fold decrease of nuclear volumes. Post-EGA nuclei are characterised by a conventional nuclear architecture with chromatin distributed throughout the nuclear space, heterochromatin enriched with histone markers for transcriptionally silent chromatin beneath the nuclear lamina and around nucleoli, as well as heterochromatin clusters and chromocenters throughout the nuclear interior. Pre- and post-EGA nuclei were recorded with the superior resolution of structured illumination microscopy to allow a quantitative analysis of the nuclear topography of H3K4me3 and RNAP II signals. These signals were highly significantly enriched in the perichromatin region (PR) surrounding the compact, transcriptionally silent interior of megabase-sized chromatin domains, which form the basic structural units of CT. The PR is in direct contact with interchromatin compartment (IC) channels starting at nuclear pores, permeating the nuclear space and harboring nuclear bodies in IC lacunas. Our findings support a model for the functional nuclear architecture based on spatially distinct, but co-aligned three-dimensional networks of an active and an inactive nuclear compartment. The active nuclear compartment is built up from the structurally and functionally interacting IC and PR, whereas the inactive nuclear compartment consists of the compact, transcriptionally silent core of chromatin domain clusters. This work is supported by the DFG (ZA 425/1-3, CR 59/29-2).

106 STUDIES OF NUCLEAR ARCHITECTURE IN MAMMALIAN PRE-IMPLANTATION EMBRYOS AND EMBRYONIC STEM CELLS USING SUPER-RESOLUTION FLUORESCENCE MICROSCOPY

Three-dimensional (3-D) super-resolution fluorescence microscopy has allowed major progress in studies of the functional nuclear organization (Markaki et al. 2010 Cold Spring Harb. Symp. Quant. Biol. 75, 475–492; Markaki et al. 2012 Bioessays 34, 412–426). We have exploited these new possibilities to explore nuclear organization at different stages of bovine pre-implantation development (4-cell, 8-cell, 16-cell, morula, and blastocyst stage). In particular, we studied the topography of RNA polymerase II and the distribution of transcriptionally competent and noncompetent chromatin using antibodies against H3K4me3 and H3K27me3, respectively. For comparison, we have started analyses of mouse pre-implantation embryos and embryonic stem cells as well. Our results support the chromosome territory-interchromatin compartment (CT-IC) model (Cremer and Cremer 2010 Cold Spring Harb. Perspect. Biol. 2, a003889; Cremer et al. 2012 In: Epigenetic Regulation and Epigenomics 451–483). In all cell types, the nuclear space is occupied by chromosome territories (CTs; Koehler et al. 2009 Exp. Cell Res. 315, 2053–2063), the interchromatin compartment (IC), and one or several nucleoli. The CTs are built up from interconnected, megabase-sized chromatin domains (CDs). These ~1-Mbp CDs may consist of a series of ~100-kbp CDs (Cremer et al. 2000 Crit. Rev. Eukaryot. Gene Expr. 10, 179–212), which globally form a compact chromatin core surrounded by a layer of decondensed chromatin, called the perichromatin region. Current evidence supports the hypothesis that the perichromatin region represents the nuclear compartment, where transcription, co-transcriptional splicing, DNA-replication, and DNA-repair take place (Rouquette et al. 2010 Int. Rev. Cell Mol. Biol. 282, 1–90). The IC provides a contiguous, crowded compartment, which starts with channels at nuclear pores and pervades the chromatin compartment both between and within CTs. Small-scale chromatin loops of the perichromatin region can protrude into the interior of IC channels allowing direct contacts between CDs in cis and trans. At other sites the IC expands to wider, chromatin-free lacunas with splicing speckles and nuclear bodies. This model is in line with a fractal higher-order chromatin arrangement at all levels from CTs, chromosome arms and bands to ~1 Mbp CDs organized as fractal globules (Mirny 2011 Chromosome Res. 19, 37–51). This work is supported by the DFG (ZA 425/1-3, CR 59/29-2).

432 INHERITANCE OF LENTIVIRAL PHOSPHOGLYCERATE KINASE-ENHANCED GREEN FLUORESCENT PROTEIN (PGK-eGFP) INTEGRANTS OF TRANSGENIC CATTLE

An alternative approach to classic techniques for the generation of transgenic livestock is the use of viral vectors. Using lentiviral vectors (LV) we previously generated transgenic founder cattle with integrants carrying phosphoglycerate kinase (PGK) promoter-enhanced green fluorescent protein (eGFP) expression cassettes (Hofmann et al. 2004 Biol. Reprod. 71, 405-409). The aim of this work was to investigate the transmission of LV-PGK-eGFP integrants through the female and male germ line of transgenic founder cattle in resulting embryos, fetuses, and offspring. The female founder animal was superovulated and artificially inseminated with a nontransgenic bull. Six of the 16 embryos obtained were transferred to synchronized recipient heifers, resulting in 2 pregnancies and birth of 1 healthy male transgenic calf, expressing eGFP as detected by in vivo imaging and real-time PCR. Cryopreserved semen of the founder bull and matured COC of nontransgenic cows were used for in vitro embryo production as previously described by Hiendleder et al. (2004 Biol. Reprod. 71, 217-223). The rates of cleavage and development to blastocysts in vitro corresponded to 52.3 ± 3.8% and 23.5 ± 4.6%, respectively. In vivo expression of eGFP was observed at blastocyst stage (Day 7 after IVF) and was seen in 93.8% (198/211) of all blastocysts. Twenty-four eGFP-positive embryos were transferred to 9 synchronized recipients. Analysis of 2 embryos flushed on Day 15, 2 fetuses recovered on Day 45, and a healthy male transgenic calf revealed consistent high-level expression of eGFP in all tissues investigated. These observations show for the first time transmission of lentiviral integrants through the germ line of female and male transgenic founder cattle. Although eGFP transgenic cattle have been produced before by nuclear transfer from transfected cells, lentiviral transgenesis has the advantage that only one copy of the provirus is integrated at a particular chromosomal integration site. High-fidelity expression of eGFP in embryos, fetuses, and offspring of founders provides an interesting tool for developmental studies in cattle, including interactions of gametes, embryos, and fetuses with their maternal environment.

239 OOCYTE MATURATION IN VITRO: PROTEOME ALTERATIONS ANALYZED BY ULTRA-SENSITIVE FLUOROCHROME LABELING AND NANO-ESI-MS-MS

In mammals, oocytes are arrested in the diplotene stage of the first prophase until the beginning of the estrous cycle. Directly before ovulation, the oocyte completes the first meiotic division and progresses to metaphase II. This process is mimicked by oocyte maturation in vitro, which is critical in assisted reproduction techniques in humans and animals. A sensitive 2-dimensional (2D) difference gel electrophoresis (DIGE) saturation labeling approach including an internal pooled standard was used for quantitative proteome profiling of immature v. in vitro-matured bovine oocytes. A mixture of 0.25 µg of oocyte sample and 0.25 µg of the internal pooled standard was separated on each analytical 2D gel, corresponding to the protein content of approximately five oocytes. In total, the study comprised 48 2D gel images representing 24 DIGE experiments [6 independent samples � 2 gels per stage (immature/mature) � 2 pH gradients]. DeCyder differential in-gel analysis (DIA; Amersham Biosciences, Piscataway, NJ, USA) detected 2244 spots (SD = 100) in pH 4–7 images, and 1291 spots (SD = 65) in pH 6–9 images. In total, 38 spots with different intensity were detected (abundance ratio ≥2; Student's t-test, P ≤ 0.01). Differently abundant spots were identified by nano-LC-MS/MS analysis of matched spots in a preparative gel of saturation-labeled protein extract from 2200 immature oocytes. Ten spots could be unambiguously identified and comprised, e.g., interesting proteins such as clusterin, 14-3-3 ε, redox enzymes, and new polymorphic forms of glutathione-S-transferases. Clusterin is suggested to interact with components of the complement membrane attack complex, and 14-3-3 ε is a mediator of the activation of the maturation promoting factor, a key enzyme of the meiosis. Our study demonstrates the feasibility of differential oocyte proteomics using saturation labeling. Several of the proteins identified in this study are already known to play an important role in oocyte maturation, which reflects the relevance and reliability of our approach. Furthermore, we found proteins which are so far unknown in the context of oocyte development. A more detailed knowledge of the role of these candidates during oocyte maturation may help to optimize the in vitro-maturation process in order to increase the rate of successful in vitro fertilization and other assisted reproduction techniques in cattle and other mammals. This work was supported by grant Deutsche Forschungsgemeinschaft (FOR 478, GRK 1029).

169 AN OPTIMIZED PROTOCOL FOR EXTRACTING RNA FROM SINGLE BOVINE OOCYTES AND BLASTOMERES

Quantitative PCR (qPCR) analysis of gene expression in single bovine oocytes or blastomeres from early preimplantation embryos needs to meet optimized requirements for the isolation of the RNA, the reverse transcription reaction, and even the qPCR. Normally, large amounts of tissues are required for extracting RNA, but the RNA recovery per embryo is too low for a reliable detection of low expressed genes. Therefore an optimized isolation method is essential for obtaining sufficient RNA recoveries of (a) a group of embryos/oocytes (n = 10), (b) a single oocyte/embryo, or (c) single blastomeres without inhibition of the subsequent steps. For each experiment studied, the RNA was reverse-transcribed with ExtremeScript-OLS� (Omni Life Science, Inc., Raynham, MA, USA) following the manufacturer's instructions. The transcript levels were analyzed by the detection of the genes STAT3 and LEPR. First, we compared different isolation protocols from the literature for the isolation of oocyte RNA[TriZol� (Invitrogen, Carlsbad, CA, USA) and RNAPure™ (Peqlab Biotechnologie, Erlangen, Germany) for isolation of total RNA; magnetic beads and Absolutely RNA™ Nanoprep (Stratogene, La Jolla, CA, USA) for mRNA; n = 12 per protocol] by measurement of the total RNA concentration (TriZol and RNAPure) and qPCR analysis (all isolation techniques). The results showed that RNAPure provided the highest transcript numbers (100% RNAPure v. 78% TriZol, 25% Nanoprep, and 5% magnetic beads, respectively; P ≤ 0.001) and also the highest total RNA concentration (2.1 ng µL–1 v. TriZol 1.5 ng µL–1 total RNA per oocyte; P ≤ 0.05). In the second experiment, we analyzed the influence of a coprecipitant [glycogen, linear acrylamide, SeeDNA (Amersham Biosciences, Freiburg, Germany); n = 12] on the RNA recovery and the inhibition of the subsequent reverse transcription and PCR processes. In the third experiment, the collection/storage of single oocytes was compared [RNAlater� (Applied Biosystems, Darmstadt, Germany) or liquid nitrogen; n = 20]. The use of the coprecipitant linear acrylamide (100% v. 80% for glycogen and 58% for SeeDNA; P ≤ 0.05) and the storage in liquid nitrogen (100% v. 84% for RNAlater; P ≤ 0.001) showed the highest RNA recoveries without inhibition. Furthermore, we analyzed (with the now optimized protocol) single blastomeres derived from 8- (n = 6) and 16-cell (n = 6) IVF embryos by mechanical treatment. The aim of this experiment was to analyze the expression divergences in blastomeres from normal cultured embryos without synchronization and, further, how many single blastomeres per embryo are required to obtain a comparable expression level of all blastomeres. The results showed that nearly 50% of an embryo was required (at least 4 blastomeres from an 8-cell and 7 blastomeres from a 16-cell embryo). These findings are mainly caused by different cell cycle phases of the analyzed blastomeres. Further studies with synchronized blastomeres are in progress. In conclusion, the present study demonstrates an effective RNA isolation method for a reliable qPCR analysis of single blastomeres. This work was supported by grant of the Deutsche Forschungsgemeinschaft (DFG) (FOR 478/1).