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1.  The Genome of the Alga-Associated Marine Flavobacterium Formosa agariphila KMM 3901T Reveals a Broad Potential for Degradation of Algal Polysaccharides 
Applied and Environmental Microbiology  2013;79(21):6813-6822.
In recent years, representatives of the Bacteroidetes have been increasingly recognized as specialists for the degradation of macromolecules. Formosa constitutes a Bacteroidetes genus within the class Flavobacteria, and the members of this genus have been found in marine habitats with high levels of organic matter, such as in association with algae, invertebrates, and fecal pellets. Here we report on the generation and analysis of the genome of the type strain of Formosa agariphila (KMM 3901T), an isolate from the green alga Acrosiphonia sonderi. F. agariphila is a facultative anaerobe with the capacity for mixed acid fermentation and denitrification. Its genome harbors 129 proteases and 88 glycoside hydrolases, indicating a pronounced specialization for the degradation of proteins, polysaccharides, and glycoproteins. Sixty-five of the glycoside hydrolases are organized in at least 13 distinct polysaccharide utilization loci, where they are clustered with TonB-dependent receptors, SusD-like proteins, sensors/transcription factors, transporters, and often sulfatases. These loci play a pivotal role in bacteroidetal polysaccharide biodegradation and in the case of F. agariphila revealed the capacity to degrade a wide range of algal polysaccharides from green, red, and brown algae and thus a strong specialization of toward an alga-associated lifestyle. This was corroborated by growth experiments, which confirmed usage particularly of those monosaccharides that constitute the building blocks of abundant algal polysaccharides, as well as distinct algal polysaccharides, such as laminarins, xylans, and κ-carrageenans.
PMCID: PMC3811500  PMID: 23995932
2.  The Dnmt2 RNA methyltransferase homolog of Geobacter sulfurreducens specifically methylates tRNA-Glu 
Nucleic Acids Research  2014;42(10):6487-6496.
Dnmt2 enzymes are conserved in eukaryotes, where they methylate C38 of tRNA-Asp with high activity. Here, the activity of one of the very few prokaryotic Dnmt2 homologs from Geobacter species (GsDnmt2) was investigated. GsDnmt2 was observed to methylate tRNA-Asp from flies and mice. Unexpectedly, it had only a weak activity toward its matching Geobacter tRNA-Asp, but methylated Geobacter tRNA-Glu with good activity. In agreement with this result, we show that tRNA-Glu is methylated in Geobacter while the methylation is absent in tRNA-Asp. The activities of Dnmt2 enzymes from Homo sapiens, Drosophila melanogaster, Schizosaccharomyces pombe and Dictyostelium discoideum for methylation of the Geobacter tRNA-Asp and tRNA-Glu were determined showing that all these Dnmt2s preferentially methylate tRNA-Asp. Hence, the GsDnmt2 enzyme has a swapped transfer ribonucleic acid (tRNA) specificity. By comparing the different tRNAs, a characteristic sequence pattern was identified in the variable loop of all preferred tRNA substrates. An exchange of two nucleotides in the variable loop of murine tRNA-Asp converted it to the corresponding variable loop of tRNA-Glu and led to a strong reduction of GsDnmt2 activity. Interestingly, the same loss of activity was observed with human DNMT2, indicating that the variable loop functions as a specificity determinant in tRNA recognition of Dnmt2 enzymes.
PMCID: PMC4041430  PMID: 24711368
3.  Targeted Methylation of the Epithelial Cell Adhesion Molecule (EpCAM) Promoter to Silence Its Expression in Ovarian Cancer Cells 
PLoS ONE  2014;9(1):e87703.
The Epithelial Cell Adhesion Molecule (EpCAM) is overexpressed in many cancers including ovarian cancer and EpCAM overexpression correlates with decreased survival of patients. It was the aim of this study to achieve a targeted methylation of the EpCAM promoter and silence EpCAM gene expression using an engineered zinc finger protein that specifically binds the EpCAM promoter fused to the catalytic domain of the Dnmt3a DNA methyltransferase. We show that transient transfection of this construct increased the methylation of the EpCAM promoter in SKOV3 cells from 4–8% in untreated cells to 30%. Up to 48% methylation was observed in stable cell lines which express the chimeric methyltransferase. Control experiments confirmed that the methylation was dependent on the fusion of the Zinc finger and the methyltransferase domains and specific for the target region. The stable cell lines with methylated EpCAM promoter showed a 60–80% reduction of EpCAM expression as determined at mRNA and protein level and exhibited a significantly reduced cell proliferation. Our data indicate that targeted methylation of the EpCAM promoter could be an approach in the therapy of EpCAM overexpressing cancers.
PMCID: PMC3906225  PMID: 24489952
4.  Ups and downs of a transcriptional landscape shape iron deficiency associated chlorosis of the maize inbreds B73 and Mo17 
BMC Plant Biology  2013;13:213.
Improving nutrient homeostasis is a major challenge of a sustainable maize cultivation, and cornerstone to ensure food supply for a growing world population. Although, iron constitutes an important nutrient, iron availability is limited. In this respect, iron deficiency associated chlorosis causes severe yield losses every year. Natural variation of the latter trait has yet not been addressed in maize and was therefore studied in the present analysis.
In this study, we i) report about the contrasting chlorosis phenotypes of the inbreds B73 and Mo17 at 10 and 300 μM iron regime, ii) identified over 400 significantly regulated transcripts (FDR < 0.05) within both inbreds at these growth conditions by deep RNA-Sequencing, iii) linked the gained knowledge with QTL information about iron deficiency related traits within the maize intermated B73 by Mo17 (IBM) population, and iv) highlighted contributing molecular pathways. In this respect, several genes within methionine salvage pathway and phytosiderophore synthesis were found to present constitutively high expression in Mo17, even under sufficient iron supply. Moreover, the same expression pattern could be observed for two putative bHLH transcription factors. In addition, a number of differentially expressed genes showed a co-localisation with QTL confidence intervals for iron deficiency related traits within the IBM population.
Our study highlights differential iron deficiency associated chlorosis between B73 and Mo17 and represents a valuable resource for differentially expressed genes upon iron limitation and chlorosis response. Besides identifying two putative bHLH transcription factors, we propose that methionine salvage pathway and sterol metabolism amongst others; underlie the contrasting iron deficiency related chlorosis phenotype of both inbreds. Altogether, this study emphasizes a contribution of selected genes and pathways on natural trait variation within the IBM population.
PMCID: PMC3881016  PMID: 24330725
Chlorosis; Iron deficiency; IBM population; Natural variation; QTL; RNA-Seq; Zea mays
5.  Roseobacter clade bacteria are abundant in coastal sediments and encode a novel combination of sulfur oxidation genes 
The ISME Journal  2012;6(12):2178-2187.
Roseobacter clade bacteria (RCB) are abundant in marine bacterioplankton worldwide and central to pelagic sulfur cycling. Very little is known about their abundance and function in marine sediments. We investigated the abundance, diversity and sulfur oxidation potential of RCB in surface sediments of two tidal flats. Here, RCB accounted for up to 9.6% of all cells and exceeded abundances commonly known for pelagic RCB by 1000-fold as revealed by fluorescence in situ hybridization (FISH). Phylogenetic analysis of 16S rRNA and sulfate thiohydrolase (SoxB) genes indicated diverse, possibly sulfur-oxidizing RCB related to sequences known from bacterioplankton and marine biofilms. To investigate the sulfur oxidation potential of RCB in sediments in more detail, we analyzed a metagenomic fragment from a RCB. This fragment encoded the reverse dissimilatory sulfite reductase (rDSR) pathway, which was not yet found in RCB, a novel type of sulfite dehydrogenase (SoeABC) and the Sox multi-enzyme complex including the SoxCD subunits. This was unexpected as soxCD and dsr genes were presumed to be mutually exclusive in sulfur-oxidizing prokaryotes. This unique gene arrangement would allow a metabolic flexibility beyond known sulfur-oxidizing pathways. We confirmed the presence of dsrA by geneFISH in closely related RCB from an enrichment culture. Our results show that RCB are an integral part of the microbial community in marine sediments, where they possibly oxidize inorganic and organic sulfur compounds in oxic and suboxic sediment layers.
PMCID: PMC3504970  PMID: 22739490
geneFISH; Roseobacter ; sediment; sulfur oxidation
6.  Transcriptome sequencing and microarray design for functional genomics in the extremophile Arabidopsis relative Thellungiella salsuginea (Eutrema salsugineum) 
BMC Genomics  2013;14:793.
Most molecular studies of plant stress tolerance have been performed with Arabidopsis thaliana, although it is not particularly stress tolerant and may lack protective mechanisms required to survive extreme environmental conditions. Thellungiella salsuginea has attracted interest as an alternative plant model species with high tolerance of various abiotic stresses. While the T. salsuginea genome has recently been sequenced, its annotation is still incomplete and transcriptomic information is scarce. In addition, functional genomics investigations in this species are severely hampered by a lack of affordable tools for genome-wide gene expression studies.
Here, we report the results of Thellungiella de novo transcriptome assembly and annotation based on 454 pyrosequencing and development and validation of a T. salsuginea microarray. ESTs were generated from a non-normalized and a normalized library synthesized from RNA pooled from samples covering different tissues and abiotic stress conditions. Both libraries yielded partially unique sequences, indicating their necessity to obtain comprehensive transcriptome coverage. More than 1 million sequence reads were assembled into 42,810 unigenes, approximately 50% of which could be functionally annotated. These unigenes were compared to all available Thellungiella genome sequence information. In addition, the groups of Late Embryogenesis Abundant (LEA) proteins, Mitogen Activated Protein (MAP) kinases and protein phosphatases were annotated in detail. We also predicted the target genes for 384 putative miRNAs. From the sequence information, we constructed a 44 k Agilent oligonucleotide microarray. Comparison of same-species and cross-species hybridization results showed superior performance of the newly designed array for T. salsuginea samples. The developed microarrays were used to investigate transcriptional responses of T. salsuginea and Arabidopsis during cold acclimation using the MapMan software.
This study provides the first comprehensive transcriptome information for the extremophile Arabidopsis relative T. salsuginea. The data constitute a more than three-fold increase in the number of publicly available unigene sequences and will greatly facilitate genome annotation. In addition, we have designed and validated the first genome-wide microarray for T. salsuginea, which will be commercially available. Together with the publicly available MapMan software this will become an important tool for functional genomics of plant stress tolerance.
PMCID: PMC3832907  PMID: 24228715
Arabidopsis thaliana; Cold acclimation; Gene annotation; LEA proteins; MAP kinases; Microarray design; microRNAs; Protein phosphatases; Thellungiella salsuginea; Transcriptome sequencing
7.  mRNA-Seq and microarray development for the Grooved carpet shell clam, Ruditapes decussatus: a functional approach to unravel host -parasite interaction 
BMC Genomics  2013;14:741.
The Grooved Carpet shell clam Ruditapes decussatus is the autochthonous European clam and the most appreciated from a gastronomic and economic point of view. The production is in decline due to several factors such as Perkinsiosis and habitat invasion and competition by the introduced exotic species, the manila clam Ruditapes philippinarum. After we sequenced R. decussatus transcriptome we have designed an oligo microarray capable of contributing to provide some clues on molecular response of the clam to Perkinsiosis.
A database consisting of 41,119 unique transcripts was constructed, of which 12,479 (30.3%) were annotated by similarity. An oligo-DNA microarray platform was then designed and applied to profile gene expression in R. decussatus heavily infected by Perkinsus olseni. Functional annotation of differentially expressed genes between those two conditionswas performed by gene set enrichment analysis. As expected, microarrays unveil genes related with stress/infectious agents such as hydrolases, proteases and others. The extensive role of innate immune system was also analyzed and effect of parasitosis upon expression of important molecules such as lectins reviewed.
This study represents a first attempt to characterize Ruditapes decussatus transcriptome, an important marine resource for the European aquaculture. The trancriptome sequencing and consequent annotation will increase the available tools and resources for this specie, introducing the possibility of high throughput experiments such as microarrays analysis. In this specific case microarray approach was used to unveil some important aspects of host-parasite interaction between the Carpet shell clam and Perkinsus, two non-model species, highlighting some genes associated with this interaction. Ample information was obtained to identify biological processes significantly enriched among differentially expressed genes in Perkinsus infected versus non-infected gills. An overview on the genes related with the immune system on R. decussatus transcriptome is also reported.
PMCID: PMC4007648  PMID: 24168212
8.  Alternative Processing as Evolutionary Mechanism for the Origin of Novel Nonprotein Coding RNAs 
Genome Biology and Evolution  2013;5(11):2061-2071.
The evolution of new genes can ensue through either gene duplication and the neofunctionalization of one of the copies or the formation of a de novo gene from hitherto nonfunctional, neutrally evolving intergenic or intronic genomic sequences. Only very rarely are entire genes created de novo. Mostly, nonfunctional sequences are coopted as novel parts of existing genes, such as in the process of exonization whereby introns become exons through changes in splicing. Here, we report a case in which a novel nonprotein coding RNA evolved by intron-sequence recruitment into its structure. cDNAs derived from rat brain small RNAs, revealed a novel small nucleolar RNA (snoRNA) originating from one of the Snord115 copies in the rat Prader–Willi syndrome locus. We suggest that a single-point substitution in the Snord115 region led to the expression of a longer snoRNA variant, designated as L-Snord115. Cell culture and footprinting experiments confirmed that a single nucleotide substitution at Snord115 position 67 destabilized the kink-turn motif within the canonical snoRNA, while distal intronic sequences provided an alternate D-box region. The exapted sequence displays putative base pairing to 28S rRNA and mRNA targets.
PMCID: PMC3845636  PMID: 24132753
evolution of novel nonprotein coding RNA variants; Prader-Willi syndrome (PWS); rat Snord115; processing mutant; snoRNA biogenesis; K-turn motif
9.  Plasticity of Animal Genome Architecture Unmasked by Rapid Evolution of a Pelagic Tunicate 
Science (New York, N.Y.)  2010;330(6009):1381-1385.
Genomes of animals as different as sponges and humans show conservation of global architecture. Here we show that multiple genomic features including transposon diversity, developmental gene repertoire, physical gene order, and intron-exon organization are shattered in the tunicate Oikopleura, belonging to the sister group of vertebrates and retaining chordate morphology. Ancestral architecture of animal genomes can be deeply modified and may therefore be largely nonadaptive. This rapidly evolving animal lineage thus offers unique perspectives on the level of genome plasticity. It also illuminates issues as fundamental as the mechanisms of intron gain.
PMCID: PMC3760481  PMID: 21097902
10.  A Rapid Transcriptome Response Is Associated with Desiccation Resistance in Aerially-Exposed Killifish Embryos 
PLoS ONE  2013;8(5):e64410.
Delayed hatching is a form of dormancy evolved in some amphibian and fish embryos to cope with environmental conditions transiently hostile to the survival of hatchlings or larvae. While diapause and cryptobiosis have been extensively studied in several animals, very little is known concerning the molecular mechanisms involved in the sensing and response of fish embryos to environmental cues. Embryos of the euryhaline killifish Fundulus heteroclitus advance dvelopment when exposed to air but hatching is suspended until flooding with seawater. Here, we investigated how transcriptome regulation underpins this adaptive response by examining changes in gene expression profiles of aerially incubated killifish embryos at ∼100% relative humidity, compared to embryos continuously flooded in water. The results confirm that mid-gastrula embryos are able to stimulate development in response to aerial incubation, which is accompanied by the differential expression of at least 806 distinct genes during a 24 h period. Most of these genes (∼70%) appear to be differentially expressed within 3 h of aerial exposure, suggesting a broad and rapid transcriptomic response. This response seems to include an early sensing phase, which overlaps with a tissue remodeling and activation of embryonic development phase involving many regulatory and metabolic pathways. Interestingly, we found fast (0.5–1 h) transcriptional differences in representatives of classical “stress” proteins, such as some molecular chaperones, members of signalling pathways typically involved in the transduction of sensor signals to stress response genes, and oxidative stress-related proteins, similar to that described in other animals undergoing dormancy, diapause or desiccation. To our knowledge, these data represent the first transcriptional profiling of molecular processes associated with desiccation resistance during delayed hatching in non-mammalian vertebrates. The exceptional transcriptomic plasticity observed in killifish embryos provides an important insight as to how the embryos are able to rapidly adapt to non-lethal desiccation conditions.
PMCID: PMC3669298  PMID: 23741328
11.  High-Resolution Transcriptome Maps Reveal Strain-Specific Regulatory Features of Multiple Campylobacter jejuni Isolates 
PLoS Genetics  2013;9(5):e1003495.
Campylobacter jejuni is currently the leading cause of bacterial gastroenteritis in humans. Comparison of multiple Campylobacter strains revealed a high genetic and phenotypic diversity. However, little is known about differences in transcriptome organization, gene expression, and small RNA (sRNA) repertoires. Here we present the first comparative primary transcriptome analysis based on the differential RNA–seq (dRNA–seq) of four C. jejuni isolates. Our approach includes a novel, generic method for the automated annotation of transcriptional start sites (TSS), which allowed us to provide genome-wide promoter maps in the analyzed strains. These global TSS maps are refined through the integration of a SuperGenome approach that allows for a comparative TSS annotation by mapping RNA–seq data of multiple strains into a common coordinate system derived from a whole-genome alignment. Considering the steadily increasing amount of RNA–seq studies, our automated TSS annotation will not only facilitate transcriptome annotation for a wider range of pro- and eukaryotes but can also be adapted for the analysis among different growth or stress conditions. Our comparative dRNA–seq analysis revealed conservation of most TSS, but also single-nucleotide-polymorphisms (SNP) in promoter regions, which lead to strain-specific transcriptional output. Furthermore, we identified strain-specific sRNA repertoires that could contribute to differential gene regulation among strains. In addition, we identified a novel minimal CRISPR-system in Campylobacter of the type-II CRISPR subtype, which relies on the host factor RNase III and a trans-encoded sRNA for maturation of crRNAs. This minimal system of Campylobacter, which seems active in only some strains, employs a unique maturation pathway, since the crRNAs are transcribed from individual promoters in the upstream repeats and thereby minimize the requirements for the maturation machinery. Overall, our study provides new insights into strain-specific transcriptome organization and sRNAs, and reveals genes that could modulate phenotypic variation among strains despite high conservation at the DNA level.
Author Summary
Many species have evolved into diverse strains with phenotypic and genotypic variations that facilitate adaptation to different ecological niches and, in the case of pathogens, to different hosts. Whereas comparison of genome sequences reveals differences and similarities among strains, the consequences of genomic variations can be tracked by studying the functional output from the genome. RNA sequencing has been revolutionizing transcriptome analyses of both pro- and eukaryotes. However, the bioinformatics-based analysis is still lagging behind, and transcriptome features are often manually annotated, which is laborious and time-consuming. This is even more compounded for the analyses of multiple strains. Here we compared the primary transcriptomes of four isolates of Campylobacter jejuni, the leading cause of bacterial gastroenteritis in humans, and provide genome-wide transcriptional start site (TSS) maps using a novel automated annotation method. Our comparative RNA–seq showed that most TSS are conserved in multiple strains, but we also observed SNP–dependent promoter usage. Furthermore, we identified a novel minimal RNA–based CRISPR immune system as well as strain-specific small RNA repertoires. Our automated, comparative TSS annotation will facilitate and improve transcriptome annotation for a wider range of organisms and provides insights into the contribution of transcriptome differences to phenotypic variation among closely related species.
PMCID: PMC3656092  PMID: 23696746
12.  Complete Genome Sequence of Methylocystis sp. Strain SC2, an Aerobic Methanotroph with High-Affinity Methane Oxidation Potential 
Journal of Bacteriology  2012;194(21):6008-6009.
Methylocystis sp. strain SC2 is an aerobic type II methanotroph isolated from a highly polluted aquifer in Germany. A specific trait of the SC2 strain is the expression of two isozymes of particulate methane monooxygenase with different methane oxidation kinetics. Here we report the complete genome sequence of this methanotroph that contains not only a circular chromosome but also two large plasmids.
PMCID: PMC3486114  PMID: 23045511
13.  Complete genome sequence of Desulfocapsa sulfexigens, a marine deltaproteobacterium specialized in disproportionating inorganic sulfur compounds 
Standards in Genomic Sciences  2013;8(1):58-68.
Desulfocapsa sulfexigens SB164P1 (DSM 10523) belongs to the deltaproteobacterial family Desulfobulbaceae and is one of two validly described members of its genus. This strain was selected for genome sequencing, because it is the first marine bacterium reported to thrive on the disproportionation of elemental sulfur, a process with a unresolved enzymatic pathway in which elemental sulfur serves both as electron donor and electron acceptor. Furthermore, in contrast to its phylogenetically closest relatives, which are dissimilatory sulfate-reducers, D. sulfexigens is unable to grow by sulfate reduction and appears metabolically specialized in growing by disproportionating elemental sulfur, sulfite or thiosulfate with CO2 as the sole carbon source. The genome of D. sulfexigens contains the set of genes that is required for nitrogen fixation. In an acetylene assay it could be shown that the strain reduces acetylene to ethylene, which is indicative for N-fixation. The circular chromosome of D. sulfexigens SB164P1 comprises 3,986,761 bp and harbors 3,551 protein-coding genes of which 78% have a predicted function based on auto-annotation. The chromosome furthermore encodes 46 tRNA genes and 3 rRNA operons.
PMCID: PMC3739170  PMID: 23961312
Sulfur-cycle; thiosulfate; sulfite; sulfur disproportionation; marine; sediment
14.  Spread of a Distinct Stx2-Encoding Phage Prototype among Escherichia coli O104:H4 Strains from Outbreaks in Germany, Norway, and Georgia 
Journal of Virology  2012;86(19):10444-10455.
Shiga toxin 2 (Stx2)-producing Escherichia coli (STEC) O104:H4 caused one of the world's largest outbreaks of hemorrhagic colitis and hemolytic uremic syndrome in Germany in 2011. These strains have evolved from enteroaggregative E. coli (EAEC) by the acquisition of the Stx2 genes and have been designated enteroaggregative hemorrhagic E. coli. Nucleotide sequencing has shown that the Stx2 gene is carried by prophages integrated into the chromosome of STEC O104:H4. We studied the properties of Stx2-encoding bacteriophages which are responsible for the emergence of this new type of E. coli pathogen. For this, we analyzed Stx bacteriophages from STEC O104:H4 strains from Germany (in 2001 and 2011), Norway (2006), and the Republic of Georgia (2009). Viable Stx2-encoding bacteriophages could be isolated from all STEC strains except for the Norwegian strain. The Stx2 phages formed lysogens on E. coli K-12 by integration into the wrbA locus, resulting in Stx2 production. The nucleotide sequence of the Stx2 phage P13374 of a German STEC O104:H4 outbreak was determined. From the bioinformatic analyses of the prophage sequence of 60,894 bp, 79 open reading frames were inferred. Interestingly, the Stx2 phages from the German 2001 and 2011 outbreak strains were found to be identical and closely related to the Stx2 phages from the Georgian 2009 isolates. Major proteins of the virion particles were analyzed by mass spectrometry. Stx2 production in STEC O104:H4 strains was inducible by mitomycin C and was compared to Stx2 production of E. coli K-12 lysogens.
PMCID: PMC3457275  PMID: 22811533
15.  A de novo assembly of the newt transcriptome combined with proteomic validation identifies new protein families expressed during tissue regeneration 
Genome Biology  2013;14(2):R16.
Notophthalmus viridescens, an urodelian amphibian, represents an excellent model organism to study regenerative processes, but mechanistic insights into molecular processes driving regeneration have been hindered by a paucity and poor annotation of coding nucleotide sequences. The enormous genome size and the lack of a closely related reference genome have so far prevented assembly of the urodelian genome.
We describe the de novo assembly of the transcriptome of the newt Notophthalmus viridescens and its experimental validation. RNA pools covering embryonic and larval development, different stages of heart, appendage and lens regeneration, as well as a collection of different undamaged tissues were used to generate sequencing datasets on Sanger, Illumina and 454 platforms. Through a sequential de novo assembly strategy, hybrid datasets were converged into one comprehensive transcriptome comprising 120,922 non-redundant transcripts with a N50 of 975. From this, 38,384 putative transcripts were annotated and around 15,000 transcripts were experimentally validated as protein coding by mass spectrometry-based proteomics. Bioinformatical analysis of coding transcripts identified 826 proteins specific for urodeles. Several newly identified proteins establish novel protein families based on the presence of new sequence motifs without counterparts in public databases, while others containing known protein domains extend already existing families and also constitute new ones.
We demonstrate that our multistep assembly approach allows de novo assembly of the newt transcriptome with an annotation grade comparable to well characterized organisms. Our data provide the groundwork for mechanistic experiments to answer the question whether urodeles utilize proprietary sets of genes for tissue regeneration.
PMCID: PMC4054090  PMID: 23425577
16.  The genome sequence of Atlantic cod reveals a unique immune system 
Nature  2011;477(7363):207-210.
Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture1,2. Here we present the genome sequence of Atlantic cod, showing evidence for complex thermal adaptations in its haemoglobin gene cluster and an unusual immune architecture compared to other sequenced vertebrates. The genome assembly was obtained exclusively by 454 sequencing of shotgun and paired-end libraries, and automated annotation identified 22,154 genes. The major histocompatibility complex (MHC) II is a conserved feature of the adaptive immune system of jawed vertebrates3,4, but we show that Atlantic cod has lost the genes for MHCII, CD4 and Ii that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions5. We find a highly expanded number of MHCI genes and a unique composition of its Toll-like receptor (TLR) families. This suggests how the Atlantic cod immune system has evolved compensatory mechanisms within both adaptive and innate immunity in the absence of MHCII. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates.
PMCID: PMC3537168  PMID: 21832995
17.  CCDC103 mutations cause primary ciliary dyskinesia by disrupting assembly of ciliary dynein arms 
Nature genetics  2012;44(6):714-719.
Cilia are essential for fertilization, respiratory clearance, cerebrospinal fluid circulation, and to establish laterality1. Cilia motility defects cause Primary Ciliary Dyskinesia (PCD, MIM 242650), a disorder affecting 1:15-30,000 births. Cilia motility requires the assembly of multisubunit dynein arms that drive cilia bending2. Despite progress in understanding the genetic basis of PCD, mutations remain to be identified for several PCD linked loci3. Here we show that the zebrafish cilia paralysis mutant schmalhanstn222 (smh) mutant encodes the coiled-coil domain containing 103 protein (Ccdc103), a foxj1a regulated gene. Screening 146 unrelated PCD families identified patients in six families with reduced outer dynein arms, carrying mutations in CCDC103. Dynein arm assembly in smh mutant zebrafish was rescued by wild-type but not mutant human CCDC103. Chlamydomonas Ccdc103 functions as a tightly bound, axoneme-associated protein. The results identify Ccdc103 as a novel dynein arm attachment factor that when mutated causes Primary Ciliary Dyskinesia.
PMCID: PMC3371652  PMID: 22581229
18.  Complete Sequence Analysis of Two Methanotroph-Specific repABC-Containing Plasmids from Methylocystis sp. Strain SC2 
Applied and Environmental Microbiology  2012;78(12):4373-4379.
The complete nucleotide sequences of two large, low-copy-number plasmids of 229.6 kb (pBSC2-1) and 143.5 kb (pBSC2-2) were determined during assembly of the whole-genome shotgun sequences of the methane-oxidizing bacterium Methylocystis sp. strain SC2. The physical existence of the two plasmids in strain SC2 was confirmed by pulsed-field gel electrophoresis followed by Southern hybridization. Both plasmids have a conserved replication module of the repABC system and carry genes involved in their faithful maintenance and conjugation. In addition, they contain genes that might be involved in essential metabolic processes. These include several heavy metal resistance genes and copper transport genes in pBSC2-1 and a complete nitrous oxide reductase operon and a pmoC singleton in pBSC2-2, the latter encoding the PmoC subunit of particulate methane monooxygenase.
PMCID: PMC3370566  PMID: 22504811
19.  Onset of Immune Senescence Defined by Unbiased Pyrosequencing of Human Immunoglobulin mRNA Repertoires 
PLoS ONE  2012;7(11):e49774.
The immune system protects us from foreign substances or pathogens by generating specific antibodies. The variety of immunoglobulin (Ig) paratopes for antigen recognition is a result of the V(D)J rearrangement mechanism, while a fast and efficient immune response is mediated by specific immunoglobulin isotypes obtained through class switch recombination (CSR). To get a better understanding on how antibody-based immune protection works and how it changes with age, the interdependency between these two parameters need to be addressed. Here, we have performed an in depth analysis of antibody repertoires of 14 healthy donors representing different gender and age groups. For this task, we developed a unique pyrosequencing approach, which is able to monitor the expression levels of all immunoglobulin V(D)J recombinations of all isotypes including subtypes in an unbiased and quantitative manner. Our results show that donors have individual immunoglobulin repertoires and cannot be clustered according to V(D)J recombination patterns, neither by age nor gender. However, after incorporating isotype-specific analysis and considering CSR information into hierarchical clustering the situation changes. For the first time the donors cluster according to age and separate into young adults and elderly donors (>50). As a direct consequence, this clustering defines the onset of immune senescence at the age of fifty and beyond. The observed age-dependent reduction of CSR ability proposes a feasible explanation why reduced efficacy of vaccination is seen in the elderly and implies that novel vaccine strategies for the elderly should include the “Golden Agers”.
PMCID: PMC3511497  PMID: 23226220
20.  Physiological and Proteomic Adaptation of “Aromatoleum aromaticum” EbN1 to Low Growth Rates in Benzoate-Limited, Anoxic Chemostats 
Journal of Bacteriology  2012;194(9):2165-2180.
“Aromatoleum aromaticum” EbN1 was cultivated at different growth rates in benzoate-limited chemostats under nitrate-reducing conditions. Physiological characteristics, proteome dynamics, phospholipid-linked fatty acid (PLFA) composition, and poly(3-hydroxybutyrate) (PHB) content were analyzed in steady-state cells at low (μlow) (0.036 h−1), medium (μmed) (0.108 h−1), and high (μhigh) (0.180 h−1) growth rates. A positive correlation to growth rate was observed for cellular parameters (cell size, and DNA and protein contents). The free energy consumed for biomass formation steadily increased with growth rate. In contrast, the energy demand for maintenance increased only from μlow to μmed and then remained constant until μhigh. The most comprehensive proteomic changes were observed at μlow compared to μhigh. Uniformly decreased abundances of protein components of the anaerobic benzoyl coenzyme A (benzoyl-CoA) pathway, central carbon metabolism, and information processing agree with a general deceleration of benzoate metabolism and cellular processes in response to slow growth. In contrast, increased abundances were observed at μlow for diverse catabolic proteins and components of uptake systems in the absence of the respective substrate (aromatic or aliphatic compounds) and for proteins involved in stress responses. This potential catabolic versatility and stress defense during slow growth may be interpreted as preparation for future needs.
PMCID: PMC3347066  PMID: 22366417
21.  Diversity, Molecular Characterization and Expression of T Cell Receptor γ in a Teleost Fish, the Sea Bass (Dicentrarchus labrax, L) 
PLoS ONE  2012;7(10):e47957.
Two lineages of T cells, expressing either the αβ T cell receptor (TR) or the γδ TR, exist in Gnathostomes. The latter type of T cells account for 1–10 % of T cells in blood and up to 30 % in the small intestine. They may recognize unconventional antigens (phosphorylated microbial metabolites, lipid antigens) without the need of major histocompatibility class I (MH1) or class II (MH2) presentation. In this work we have described cloning and structural characterization of TR -chain (TRG) from the teleost Dicentrarchus labrax. Further, by means of quantitative PCR analysis, we analyzed TRG expression levels both in poly I:C stimulated leukocytes in vitro, and following infection with betanodavirus in vivo. Two full length cDNAs relative to TRG, with the highest peptide and nucleotide identity with Japanese flounder, were identified. A multiple alignment analysis showed the conservation of peptides fundamental for TRG biological functions, and of the FGXG motif in the FR4 region, typical of most TR and immunoglobulin light chains. A 3D structure consisting of two domains mainly folded as beta strands with a sandwich architecture for each domain was also reported. TRG CDR3 of 8–18 AA in length and diversity in the TRG rearrangements expressed in thymus and intestine for a given V/C combination were evidenced by junction length spectratyping. TRG mRNA expression levels were high in basal conditions both in thymus and intestine, while in kidney and gut leukocytes they were up-regulated after in vitro stimulation by poly I:C. Finally, in juveniles the TRG expression levels were up-regulated in the head kidney and down-regulated in intestine after in vivo infection with betanodavirus. Overall, in this study the involvement of TRG-bearing T cells during viral stimulation was described for the first time, leading to new insights for the identification of T cell subsets in fish.
PMCID: PMC3485050  PMID: 23133531
22.  Maternal 3’UTRs: from egg to onset of zygotic transcription in Atlantic cod 
BMC Genomics  2012;13:443.
Zygotic transcription in fish embryos initiates around the time of gastrulation, and all prior development is initiated and controlled by maternally derived messenger RNAs. Atlantic cod egg and embryo viability is variable, and it is hypothesized that the early development depends upon the feature of these maternal RNAs. Both the length and the presence of specific motifs in the 3’UTR of maternal RNAs are believed to regulate expression and stability of the maternal transcripts. Therefore, the aim of this study was to characterize the overall composition and 3’UTR structure of the most common maternal RNAs found in cod eggs and pre-zygotic embryos.
22229 Sanger-sequences were obtained from 3’-end sequenced cDNA libraries prepared from oocyte, 1-2 cell, blastula and gastrula stages. Quantitative PCR revealed that EST copy number below 9 did not reflect the gene expression profile. Consequently genes represented by less than 9 ESTs were excluded from downstream analyses, in addition to sequences with low-quality gene hits. This provided 12764 EST sequences, encoding 257 unique genes, for further analysis. Mitochondrial transcripts accounted for 45.9-50.6% of the transcripts isolated from the maternal stages, but only 12.2% of those present at the onset of zygotic transcription. 3’UTR length was predicted in nuclear sequences with poly-A tail, which identified 191 3’UTRs. Their characteristics indicated a more complex regulation of transcripts that are abundant prior to the onset of zygotic transcription. Maternal and stable transcripts had longer 3’UTR (mean 187.1 and 208.8 bp) and more 3’UTR isoforms (45.7 and 34.6%) compared to zygotic transcripts, where 15.4% had 3’UTR isoforms and the mean 3’UTR length was 76 bp. Also, diversity and the amount of putative polyadenylation motifs were higher in both maternal and stable transcripts.
We report on the most pronounced processes in the maternally transferred cod transcriptome. Maternal stages are characterized by a rich abundance of mitochondrial transcripts. Maternal and stable transcripts display longer 3'UTRs with more variation of both polyadenylation motifs and 3'UTR isoforms. These data suggest that cod eggs possess a complex array of maternal RNAs which likely act to tightly regulate early developmental processes in the newly fertilized egg.
PMCID: PMC3462720  PMID: 22937762
3’UTR; Sequence/EST filtering; External spiking; Transcriptome; Teleost; Embryonic development
23.  Role of Prostaglandin Pathway and Alendronate-Based Carriers to Enhance Statin-induced Bone 
Molecular pharmaceutics  2011;8(4):1035-1042.
This study investigated the role of the prostaglandin (PG) pathway in locally-applied, simvastatin-induced oral bone growth. The possibility of enhancing long-term bone augmentation with an alendronate-based carrier was initiated.
Mandibles of 44 mature female rats were treated bilaterally with the following combinations: 2 mg simvastatin in ethanol (SIM-EtOH), EtOH, 2 mg simvastatin acid complexed with alendronate-beta-cyclodextrin conjugate (SIM/ALN-CD), ALN-CD, or ALN. Bone wash technology (injection of PBS and recollection by suction) was used to sample injection sites at baseline (day 0), and 3, 7, 14 and 21 days post-treatment. After 21-24 or 48 days, histomorphometric analysis was done. The amount of PGE2 in bone wash fluid was measured by ELISA, normalized by total protein, and compared between high and low bone growth groups (ANOVA) and correlated with subsequent bone histology at 21 days (Spearman). SIM-stimulated PGE2 synthase and EP4 receptor mRNA in murine osteoblast and fibroblast cell lines were evaluated with real-time PCR.
Single injections of 2 mg SIM-EtOH induced significantly more new bone than control side after 21 days. PGE2/protein ratios peaked at day 7 and were correlated with the subsequent 21-day new bone width. The correlations at day 14 between PGE2 and new bone width changed to a negative relationship in the test group. SIM-stimulated osteoblasts expressed increased mRNA levels of PGE receptor EP4, while SIM activated PGE synthesis in fibroblasts. SIM/ALN-CD tended to preserve bone long-term.
Findings suggest that PGE pathway activation and higher levels of PGE2 during the first week following SIM-induced bone growth are desirable, and alendronate-beta-cyclodextrin conjugates not only act as tissue-specific carriers, but preserve new bone.
PMCID: PMC3148302  PMID: 21438610
PGE2; simvastatin; alendronate; cyclodextrin; bone growth
24.  High-throughput polymorphism detection and genotyping in Brassica napus using next-generation RAD sequencing 
BMC Genomics  2012;13:281.
The complex genome of rapeseed (Brassica napus) is not well understood despite the economic importance of the species. Good knowledge of sequence variation is needed for genetics approaches and breeding purposes. We used a diversity set of B. napus representing eight different germplasm types to sequence genome-wide distributed restriction-site associated DNA (RAD) fragments for polymorphism detection and genotyping.
More than 113,000 RAD clusters with more than 20,000 single nucleotide polymorphisms (SNPs) and 125 insertions/deletions were detected and characterized. About one third of the RAD clusters and polymorphisms mapped to the Brassica rapa reference sequence. An even distribution of RAD clusters and polymorphisms was observed across the B. rapa chromosomes, which suggests that there might be an equal distribution over the Brassica oleracea chromosomes, too. The representation of Gene Ontology (GO) terms for unigenes with RAD clusters and polymorphisms revealed no signature of selection with respect to the distribution of polymorphisms within genes belonging to a specific GO category.
Considering the decreasing costs for next-generation sequencing, the results of our study suggest that RAD sequencing is not only a simple and cost-effective method for high-density polymorphism detection but also an alternative to SNP genotyping from transcriptome sequencing or SNP arrays, even for species with complex genomes such as B. napus.
PMCID: PMC3442993  PMID: 22726880
Brassica napus; Restriction-site associated DNA; Next-generation sequencing; Single nucleotide polymorphism; Genotyping by sequencing; Genetic diversity
25.  Serum Bone Biomarkers and Oral/Systemic Bone Loss in Humans 
Journal of dental research  2011;90(6):747-751.
We recently reported that subantimicrobial dose doxycycline (SDD) significantly reduced serum bone-resorption biomarkers in subgroups of postmenopausal women. We hypothesize that changes in serum bone biomarkers are associated not only with systemic bone mineral density (BMD) changes, but also with alveolar bone changes over time. One hundred twenty-eight eligible postmenopausal women with periodontitis and systemic osteopenia were randomly assigned to receive SDD or placebo tablets twice daily for two years adjunctive to periodontal maintenance. Sera were analyzed for bone biomarkers. As expected, two-year changes in a serum bone biomarker were significantly associated with systemic BMD loss at the lumbar spine (osteocalcin, bone turnover biomarker, p=0.0002) and femoral neck (osteocalcin p=0.0025). Two year changes in serum osteocalcin and serum pyridinoline-crosslink fragment of type I collagen (ICTP; bone-resorption biomarker) were also significantly associated with alveolar bone density loss (p<0.0001) and alveolar bone height loss (p=0.0008), respectively. Thus, we have shown that serum bone biomarkers are associated with not only systemic BMD loss, but with alveolar bone loss as well.
PMCID: PMC3092793  PMID: 21422479
subantimicrobial dose doxycycline; periodontitis; osteopenia; serum biomarkers; bone; postmenopausal

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