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).

Haplotyping of TNFalpha gene promoter using melting temperature analysis: detection of a novel -856(G/A) mutation

Tumor necrosis factor alpha (TNFalpha) is a potent cytokine with a wide range of pro-inflammatory activities and plays a critical role in the pathogenesis of a number of infectious, inflammatory, autoimmune, and metabolic diseases. We determined four single-nucleotide polymorphisms (SNPs), -1031(C/T), -863(C/A), -857(C/T), and -308(G/A) in the TNFalpha promoter region using melting temperature analysis, among 1451 geriatric autopsy samples. Two adjacent SNPs, -863(C/A) and -857(C/T), were directly assayed by a single probe reaction, which correctly determined three of four expected haplotypes. Sequence confirmation related that the most rare haplotype (8/2902 chromosomes, frequency: 0.26%) contains a novel mutation of -856(G/A), instead of the predicted haplotype. These results indicate that melting temperature analysis provides a robust method to determine the polymorphisms in the TNFalpha promoter.

Genotools SNP manager: a new software for automated high-throughput MALDI-TOF mass spectrometry SNP genotyping

Analysis of single nucleotide polymorphisms (SNPs) is a rapidly growing field of research that provides insights into the most common type of differences between individual genomes. The resulting information has a strong impact in the fields of pharmacogenomics, drug development, forensic medicine, and diagnostics of specific disease markers. The technique of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has been shown to be a highly suitable tool for the analysis of DNA. It supplies a very versatile method for addressing a high-throughput SNP genotyping approach. Here, we present the Bruker genotools SNP MANAGER, a new software tool suitable for highly automated MALDI-TOF MS SNP genotyping. The genotools SNP MANAGER administers the sample preparation data, calculates masses of allele-specific primer extension products, performs genotyping analysis, and displays the results. In the current study, we have used the genotools SNP MANAGER to perform an automated duplex SNP analysis of two biallelic markers from the promoter of the gene encoding the inflammatory mediator interleukin-6.

Overexpression of insulin-like growth factor-binding protein-2 in transgenic mice reduces postnatal body weight gain

Insulin-like growth factor (IGF)-binding protein-2 (IGFBP-2) has been shown to inhibit IGF-dependent cell proliferation in a number of in vitro studies. However, no in vivo model of IGFBP-2 overexpression has been established so far. Therefore, we have generated transgenic mice, in which expression of a mouse IGFBP-2 complementary DNA is controlled by the cytomegalovirus (CMV) promoter. In two independent transgenic strains, transgene expression was highest in pancreas and stomach, followed by skeletal muscle, heart, colon, spleen, adipose tissue, brain, and kidney. Within the pancreas, IGFBP-2 expression was found in the islets but not in the exocrine part. Serum IGFBP-2 levels of CMV-IGFBP-2 transgenic mice were about 3-fold (P < 0.05) increased, compared with controls, whereas serum levels of IGF-I and IGF-II were unaffected by IGFBP-2 overexpression. Fasted serum glucose and fasted insulin levels were slightly reduced in transgenic mice, compared with controls. Postprandial serum glucose insulin levels were not affected by the genotype. At days later than 23, body weights of transgenic mice were significantly (P < 0.05) reduced in both sexes, compared with nontransgenic littermates. This reduction in body weight was mainly attributable to significantly (P < 0.05) lower carcass weights of CMV-IGFBP-2 transgenic vs. control mice. In contrast, absolute organ weights were not (or only as a tendency) reduced, except for the weight of the spleen, which was significantly (P < 0.05) lower in male transgenic than in control mice. Our data suggest that IGFBP-2 represents a negative regulator of postnatal growth in mice, potentially by reducing the bioavailability of IGF-I.