Project description:Most available knowledge on fungal arginine metabolism is derived from studies on Saccharomyces cerevisiae, in which arginine catabolism is initiated by releasing urea via the arginase reaction. Orthologs of the S. cerevisiae genes encoding the first three enzymes in the arginase pathway were cloned from Kluyveromyces lactis and shown to functionally complement the corresponding deletion in S. cerevisiae. Surprisingly, deletion of the single K. lactis arginase gene KlCAR1 did not completely abolish growth on arginine as nitrogen source. Growth rate of mutant strongly increased during serial transfer in shake-flask cultures. A combination of RNAseq-based transcriptome analysis and 13C-15N-based flux analysis was used to elucidate the arginase-independent pathway. Isotopic 13C15N-enrichment in ?-aminobutyrate revealed succinate as the entry point in the TCA cycle of the alternative pathway. Transcript analysis combined with enzyme activity measurements indicated increased expression in the Klcar1? mutant of a guanidinobutyrase (EC.3.5.3.7), an enzyme not previously demonstrated in fungi. Expression of the K. lactis KLLA0F27995g (renamed KlGBU1) encoding guanidinobutyrase enabled S. cerevisiae to use guanidinobutyrate as sole nitrogen source and its deletion in K. lactis almost completely abolish growth on this nitrogen source. Phylogenetic analysis suggests that this enzyme activity is widespread in fungi. The goal of the present study was to characterize arginine catabolism in K. lactis. To this end, CAR1, CAR2 and PRO3 orthologs in K. lactis were identified and functionally analysed by deletion, expression in S. cerevisiae and enzyme activity assays. Since deletion of the arginase gene in K. lactis was found not to completely abolish growth on arginine as a sole nitrogen source, the alternative pathway for arginine catabolism operating in this yeast was studied by a combination of transcriptome analysis, 13C and 15N isotope-based flux analysis and enzyme activity assays in cell extracts. To investigate arginine metabolism in the arginase-negative K. lactis strain, strains GG1632 (Klku80? KlCAR1 reference strain) and IMS0367 (Klcar1? Arg+) were grown in aerobic bioreactor batch cultures on glucose chemically defined medium with arginine as sole nitrogen source. RNA sequencing of samples taken during the exponential phase of growth on glucose-arginine media of the reference strain G1631 and the arginase less strain IMS0367 were compared resulting in the characterization of a new function.

Project description:To ensure that the pool of precursor amino acids utilized for protein synthesis is completely labeled prior to the first labeling time-point, we conducted an isotopomer analysis. After adaption to media, cells were plated at a density of 500,000 cells per 10 cm plate. 8 days after plating, the confluent quiescent cultures were switched to 15N labeling medium. Cells were collected after 0h, 6h, 1d, 2d, 4d of labeling, washed with PBS and cell pellets were frozen prior to further analysis. 15N labeling medium was made from “Cell free” Amino Acid Mix (20AA, U-15N, 96-98%)(Cambridge Isotope Laboratories) and supplemented with 15% dialyzed fetal bovine serum (Thermo Scientific), 100U/mL penicillin, 100U/mL streptomycin. 1g is used for making 702mL labeling medium. The final amino acids concentrations in 15N labeling medium are as following: Alanine: 0.1140 g/L, Arginine: 0.0499 g/L, Asparagine: 0.0940 g/L, Aspartic acid: 0.1353 g/L, Cystine: 0.01140 g/L, Glutamic acid: 0.1852 g/L, Glutamine: 0.0869 g/L, Glycine: 0.0698 g/L, Histidine: 0.0157 g/L, Isoleucine: 0.0698 g/L, Leucine: 0.1211 g/L, Lysine: 0.0527 g/L, Methionine: 0.0228 g/L, Phenylalanine: 0.0541 g/L, Proline: 0.0299 g/L, Serine: 0.0541 g/L, Threonine: 0.0741 g/L, Tryptophan: 0.0456 g/L, Tyrosine: 0.0613g/L, Valine: 0.0798 g/L. LC-MS/MS and quantitative analysis of isotopic envelopes and 15N incorporation of peptides was conducted as described in (Zhang et al., 2014). The data indicate that when exposed to fully 15N-labeled media (where all 20 natural amino acids are isotopically labeled), the fraction of proteins that are synthesized within the first day are almost fully labeled. Thus, the extent of fractional labeling is almost exclusively influenced by the kinetics of protein turnover rather than amino acid uptake and recycling within the cell. Table of files Cells Time points Labeling Fractionation Raw Data Filenames Wildtype 0d, 1d,2d,4d,7d13C 6Lys, 6Arg& 15N No 0d.raw 1d.raw 2d.raw 4d.raw 7d.raw

Project description:Whereas cloning mammals by direct somatic cell nuclear transfer has been successful using a wide range of donor cell types, neurons from adult brain remain M-bM-^@M-^\unclonableM-bM-^@M-^] for unknown reasons. Here we examined whether neurons from adult mice could be cloned, using a combination of two epigenetic approaches. First, we used a specific antibody to discover cell types with reduced amounts of a repressive histone mark - dimethylated histone H3 lysine 9 (H3K9me2) - and identified CA1 pyramidal cells in the hippocampus and Purkinje cells in the cerebellum as candidates. Second, reconstructed embryos were treated with trichostatin A (TSA), a potent histone deacetylase inhibitor. Using CA1 cells, cloned offspring were obtained at high rates, reaching 10.2% and 4.6% (per embryos transferred) for male and female donors, respectively. Cerebellar Purkinje cell nuclei were too large to maintain their genetic integrity during nuclear transfer, leading to developmental arrest of embryos. However, gene expression analysis using cloned blastocysts corroborated a high rate of genomic reprogrammability of CA1 pyramidal and Purkinje cells. Neurons from the hippocampal dentate gyrus and cerebral cortex, which had higher amounts of H3K9me2, could also be used for producing cloned offspring, but the efficiencies were low. A more thorough analysis revealed that TSA treatment was essential for cloning adult neuronal cells. This study demonstrated for the first time that adult neurons could be cloned by nuclear transfer. Furthermore, our data imply that reduced amounts of H3K9me2 and increased histone acetylation appear to act synergistically to improve the development of cloned embryos. Comparative gene expression analyses using blastocysts of cloned embryos were performed by microarray. Cloned embryos were produced with three different types of donor cells (neonatal Sertoli cells, CA1 pyramidal cells and Purkinje cells) and all cloned embryos were treated with Trichostatin A (TSA). Each embryos were cultured for 96 h and blastocysts derived from each donor cell types were subjected to gene expression microarray. For comparison of gene expression, the data sets of control sex- and genotype-matched embryos produced by in vitro fertilization and SCNT-derived blastocysts from cumulus cells treated with TSA from our previous paper (Inoue K. et al. Science 2010) were also used.

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Incorporation of isotopically labeled amino acids in live mouse zygotes as means to understand the oocyte to embryo transition

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