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1.
Life Sci Alliance ; 7(2)2024 02.
Article in English | MEDLINE | ID: mdl-37989525

ABSTRACT

The genome is organized in functional compartments and structural domains at the sub-megabase scale. How within these domains interactions between numerous cis-acting enhancers and promoters regulate transcription remains an open question. Here, we determined chromatin folding and composition over several hundred kb around estrogen-responsive genes in human breast cancer cell lines after hormone stimulation. Modeling of 5C data at 1.8 kb resolution was combined with quantitative 3D analysis of multicolor FISH measurements at 100 nm resolution and integrated with ChIP-seq data on transcription factor binding and histone modifications. We found that rapid estradiol induction of the progesterone gene expression occurs in the context of preexisting, cell type-specific chromosomal architectures encompassing the 90 kb progesterone gene coding region and an enhancer-spiked 5' 300 kb upstream genomic region. In response to estradiol, interactions between estrogen receptor α (ERα) bound regulatory elements are reinforced. Whereas initial enhancer-gene contacts coincide with RNA Pol 2 binding and transcription initiation, sustained hormone stimulation promotes ERα accumulation creating a regulatory hub stimulating transcript synthesis. In addition to implications for estrogen receptor signaling, we uncover that preestablished chromatin architectures efficiently regulate gene expression upon stimulation without the need for de novo extensive rewiring of long-range chromatin interactions.


Subject(s)
Breast Neoplasms , Estrogen Receptor alpha , Humans , Female , Estrogen Receptor alpha/genetics , Estrogen Receptor alpha/metabolism , Progesterone , Enhancer Elements, Genetic/genetics , Chromatin/genetics , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Estradiol/pharmacology
2.
Microbiome ; 10(1): 1, 2022 01 04.
Article in English | MEDLINE | ID: mdl-34980280

ABSTRACT

BACKGROUND: Previous evidence indicates associations between the female reproductive tract microbiome composition and reproductive outcome in infertile patients undergoing assisted reproduction. We aimed to determine whether the endometrial microbiota composition is associated with reproductive outcomes of live birth, biochemical pregnancy, clinical miscarriage or no pregnancy. METHODS: Here, we present a multicentre prospective observational study using 16S rRNA gene sequencing to analyse endometrial fluid and biopsy samples before embryo transfer in a cohort of 342 infertile patients asymptomatic for infection undergoing assisted reproductive treatments. RESULTS: A dysbiotic endometrial microbiota profile composed of Atopobium, Bifidobacterium, Chryseobacterium, Gardnerella, Haemophilus, Klebsiella, Neisseria, Staphylococcus and Streptococcus was associated with unsuccessful outcomes. In contrast, Lactobacillus was consistently enriched in patients with live birth outcomes. CONCLUSIONS: Our findings indicate that endometrial microbiota composition before embryo transfer is a useful biomarker to predict reproductive outcome, offering an opportunity to further improve diagnosis and treatment strategies. Video Abstract.


Subject(s)
Microbiota , Dysbiosis/microbiology , Embryo Transfer , Female , Humans , Live Birth , Microbiota/genetics , Pregnancy , RNA, Ribosomal, 16S/genetics
3.
J Orthop ; 25: 237-243, 2021.
Article in English | MEDLINE | ID: mdl-34099953

ABSTRACT

CLINICAL TRIAL NUMBER: NCT04580069. BACKGROUND: Total knee arthroplasty is associated with an elevated inflammatory response both at a local and systemic level. The main objective of this study is to demonstrate the effectiveness of lymphatic drainage and connective tissue techniques in modulating systemic inflammation. Another objective is to evaluate the existence, at baseline, of a correlation between the inflammation indices and the level of adherence to the Mediterranean diet. METHODS: 34 patients were recruited, and divided into three groups. The control group followed the normal rehabilitation protocol. The other two groups were subjected, in addition to the standard treatment, to manual lymphatic drainage treatment or connective tissue techniques. The outcomes were recorded in three stages: upon entering the hospital, 1 week after entry and at follow-up 21 days after surgery. RESULTS: The results of the study showed that both methods, compared with the standard treatment only, positively influenced the final outcomes. In regard to the systemic inflammation, lymphatic drainage and connective techniques showed equal efficacy and similar timing in modulating ESR, while they differ in how they affect CRP. With regard to the local inflammation, the effectiveness of both methods was confirmed with some differences in the location. Finally, analysis of the correlation between inflammatory T0 indices and adherence to the Mediterranean diet showed that patients with higher adhesion index have on average lower PCR, EDO and EDU values. CONCLUSIONS: The post-surgical inflammatory pattern can be positively modified by the rehabilitation methods analyzed, albeit with different methodologies and timing.The influence of the diet on inflammatory parameters, although less evident, seems to show encouraging results worth of further studies.

4.
Am J Obstet Gynecol ; 222(4): 296-305, 2020 04.
Article in English | MEDLINE | ID: mdl-32057732

ABSTRACT

Investigation of the microbial community in the female reproductive tract with the use of sequencing techniques has revealed that endometrial samples obtained through a transvaginal catheter are dominated by Lactobacillus species. Dysbiotic changes in the endometrial microbiota may be associated with implantation failure or early spontaneous abortion in patients who undergo assisted reproductive technology treatment. Whether or not there is an endometrial microbiota in early pregnancy is unknown. Herein we describe, the human endometrial microbiota in a patient who subsequently had an 8th week spontaneous clinical miscarriage with euploid embryos in the next cycle and, for the first time, during a successful pregnancy in which the endometrial fluid was sampled at 4 weeks of gestation. The microbial profile found on the endometrial sample before the spontaneous abortion had higher bacterial diversity and lower Lactobacillus abundance than the endometrial fluid from the healthy pregnancy. Functional metagenomics detected different Lactobacillus species between the 2 samples. Lactobacillus crispatus was present in the endometrium before the spontaneous abortion, as were other bacteria involved in dysbiosis, which had an unstable functional pattern characterized by transposases and insertion elements. Lactobacillus iners was the most prevalent microbe found in the endometrium during early pregnancy; its presence was associated with defense mechanisms and basal functions. These novel observations prompt future investigations to understand the potential implications of microbiology on healthy and pathologic human pregnancy.


Subject(s)
Abortion, Spontaneous/microbiology , Dysbiosis/microbiology , Endometrium/microbiology , Lactobacillus crispatus/isolation & purification , Lactobacillus/isolation & purification , Adult , Female , Humans , Lactobacillus/genetics , Lactobacillus crispatus/genetics , Metagenome , Pregnancy , Pregnancy Trimester, First
5.
Genetics ; 214(3): 651-667, 2020 03.
Article in English | MEDLINE | ID: mdl-31907200

ABSTRACT

The three-dimensional (3D) organization of chromosomes can influence transcription. However, the frequency and magnitude of these effects remain debated. To determine how changes in chromosome positioning affect transcription across thousands of genes with minimal perturbation, we characterized nuclear organization and global gene expression in budding yeast containing chromosome fusions. We used computational modeling and single-cell imaging to determine chromosome positions, and integrated these data with genome-wide transcriptional profiles from RNA sequencing. We find that chromosome fusions dramatically alter 3D nuclear organization without leading to strong genome-wide changes in transcription. However, we observe a mild but significant and reproducible increase in the expression of genes displaced away from the periphery. The increase in transcription is inversely proportional to the propensity of a given locus to be at the nuclear periphery; for example, a 10% decrease in the propensity of a gene to reside at the nuclear envelope is accompanied by a 10% increase in gene expression. Modeling suggests that this is due to both deletion of telomeres and to displacement of genes relative to the nuclear periphery. These data suggest that basal transcriptional activity is sensitive to radial changes in gene position, and provide insight into the functional relevance of budding yeast chromosome-level 3D organization in gene expression.


Subject(s)
Chromosomes, Fungal/genetics , Genome, Fungal/genetics , Molecular Conformation , Saccharomyces cerevisiae/genetics , Cell Nucleus/genetics , Cell Nucleus/ultrastructure , Chromosomes, Fungal/ultrastructure , Gene Expression Regulation, Fungal/genetics , Nuclear Envelope/genetics , Nuclear Envelope/ultrastructure , Saccharomyces cerevisiae/ultrastructure , Telomere/genetics , Telomere/ultrastructure
6.
Pathogens ; 8(4)2019 Oct 24.
Article in English | MEDLINE | ID: mdl-31653041

ABSTRACT

Investigation of the microbial community in the female reproductive tract has revealed that the replacement of a community dominated by Lactobacillus with pathogenic bacteria may be associated with implantation failure or early spontaneous abortion in patients undergoing assisted reproductive technology (ART) treatment. Herein we describe taxonomically and functionally the endometrial microbiome of an infertile patient with repeated reproductive failures (involving an ectopic pregnancy and two clinical miscarriages). The microbiological follow-up is presented over 18-month in which the microbiota was evaluated in six endometrial fluid samples. The microbial profile of 16S rRNA gene sequencing showed a persistent infection with Gardnerella and other bacterial taxa such as Atopobium and Bifidobacterium. In addition, taxonomic and functional analysis by whole metagenome sequencing in the endometrial fluid sample collected before one clinical miscarriage suggested the presence of multiple Gardnerella vaginalis clades with a greater abundance of clade 4, usually associated with metronidazole resistance. These results revealed a persistent G. vaginalis endometrial colonization presenting genetic features consistent with antimicrobial resistance, biofilm formation, and other virulence factors, which could be related to the reproductive failure observed.

7.
Am J Obstet Gynecol ; 218(6): 602.e1-602.e16, 2018 06.
Article in English | MEDLINE | ID: mdl-29477653

ABSTRACT

BACKGROUND: Chronic endometritis is a persistent inflammation of the endometrial mucosa caused by bacterial pathogens such as Enterobacteriaceae, Enterococcus, Streptococcus, Staphylococcus, Mycoplasma, and Ureaplasma. Although chronic endometritis can be asymptomatic, it is found in up to 40% of infertile patients and is responsible for repeated implantation failure and recurrent miscarriage. Diagnosis of chronic endometritis is based on hysteroscopy of the uterine cavity, endometrial biopsy with plasma cells being identified histologically, while specific treatment is determined based on microbial culture. However, not all microorganisms implicated are easily or readily culturable needing a turnaround time of up to 1 week. OBJECTIVE: We sought to develop a molecular diagnostic tool for chronic endometritis based on real-time polymerase chain reaction equivalent to using the 3 classic methods together, overcoming the bias of using any of them alone. STUDY DESIGN: Endometrial samples from patients assessed for chronic endometritis (n = 113) using at least 1 or several conventional diagnostic methods namely histology, hysteroscopy, and/or microbial culture, were blindly evaluated by real-time polymerase chain reaction for the presence of 9 chronic endometritis pathogens: Chlamydia trachomatis, Enterococcus, Escherichia coli, Gardnerella vaginalis, Klebsiella pneumoniae, Mycoplasma hominis, Neisseria gonorrhoeae, Staphylococcus, and Streptococcus. The sensitivity and specificity of the molecular analysis vs the classic diagnostic techniques were compared in the 65 patients assessed by all 3 recognized classic methods. RESULTS: The molecular method showed concordant results with histological diagnosis in 30 samples (14 double positive and 16 double negative) with a matching accuracy of 46.15%. Concordance of molecular and hysteroscopic diagnosis was observed in 38 samples (37 double positive and 1 double negative), with an accuracy of 58.46%. When the molecular method was compared to microbial culture, concordance was present in 37 samples (22 double positive and 15 double negative), a matching rate of 56.92%. When cases of potential contamination and/or noncultivable bacteria were considered, the accuracy increased to 66.15%. Of these 65 patients, only 27 patients had consistent histological + hysteroscopic diagnosis, revealing 58.64% of nonconcordant results. Only 13 of 65 patients (20%) had consistent histology + hysteroscopy + microbial culture results. In these cases, the molecular microbiology matched in 10 cases showing a diagnostic accuracy of 76.92%. Interestingly, the molecular microbiology confirmed over half of the isolated pathogens and provided additional detection of nonculturable microorganisms. These results were confirmed by the microbiome assessed by next-generation sequencing. In the endometrial samples with concordant histology + hysteroscopy + microbial culture results, the molecular microbiology diagnosis demonstrates 75% sensitivity, 100% specificity, 100% positive and 25% negative predictive values, and 0% false-positive and 25% false-negative rates. CONCLUSION: The molecular microbiology method describe herein is a fast and inexpensive diagnostic tool that allows for the identification of culturable and nonculturable endometrial pathogens associated with chronic endometritis. The results obtained were similar to all 3 classic diagnostic methods together with a degree of concordance of 76.92% providing an opportunity to improve the clinical management of infertile patients with a risk of experiencing this ghost endometrial pathology.


Subject(s)
Bacterial Infections/diagnosis , DNA, Bacterial/analysis , Endometritis/diagnosis , Endometrium/pathology , Hysteroscopy , Adult , Asymptomatic Infections , Bacterial Infections/microbiology , Bacterial Infections/pathology , Biopsy , Chlamydia Infections/diagnosis , Chlamydia Infections/microbiology , Chlamydia Infections/pathology , Chlamydia trachomatis/genetics , Chronic Disease , Culture Techniques , Endometritis/complications , Endometritis/microbiology , Endometritis/pathology , Endometrium/microbiology , Enterococcus/genetics , Escherichia coli/genetics , Escherichia coli Infections/diagnosis , Escherichia coli Infections/microbiology , Escherichia coli Infections/pathology , Female , Gardnerella vaginalis/genetics , Gonorrhea/diagnosis , Gonorrhea/microbiology , Gonorrhea/pathology , Gram-Positive Bacterial Infections/diagnosis , Gram-Positive Bacterial Infections/microbiology , Gram-Positive Bacterial Infections/pathology , High-Throughput Nucleotide Sequencing , Humans , Infertility, Female/complications , Klebsiella Infections/diagnosis , Klebsiella Infections/microbiology , Klebsiella Infections/pathology , Klebsiella pneumoniae/genetics , Middle Aged , Mycoplasma Infections/diagnosis , Mycoplasma Infections/microbiology , Mycoplasma Infections/pathology , Mycoplasma hominis/genetics , Neisseria gonorrhoeae/genetics , Pathology, Molecular , Plasma Cells/pathology , Real-Time Polymerase Chain Reaction , Sensitivity and Specificity , Sequence Analysis, DNA , Staphylococcal Infections/diagnosis , Staphylococcal Infections/microbiology , Staphylococcal Infections/pathology , Staphylococcus/genetics
8.
PLoS Comput Biol ; 13(7): e1005665, 2017 Jul.
Article in English | MEDLINE | ID: mdl-28723903

ABSTRACT

The sequence of a genome is insufficient to understand all genomic processes carried out in the cell nucleus. To achieve this, the knowledge of its three-dimensional architecture is necessary. Advances in genomic technologies and the development of new analytical methods, such as Chromosome Conformation Capture (3C) and its derivatives, provide unprecedented insights in the spatial organization of genomes. Here we present TADbit, a computational framework to analyze and model the chromatin fiber in three dimensions. Our package takes as input the sequencing reads of 3C-based experiments and performs the following main tasks: (i) pre-process the reads, (ii) map the reads to a reference genome, (iii) filter and normalize the interaction data, (iv) analyze the resulting interaction matrices, (v) build 3D models of selected genomic domains, and (vi) analyze the resulting models to characterize their structural properties. To illustrate the use of TADbit, we automatically modeled 50 genomic domains from the fly genome revealing differential structural features of the previously defined chromatin colors, establishing a link between the conformation of the genome and the local chromatin composition. TADbit provides three-dimensional models built from 3C-based experiments, which are ready for visualization and for characterizing their relation to gene expression and epigenetic states. TADbit is an open-source Python library available for download from https://github.com/3DGenomes/tadbit.


Subject(s)
Chromatin/genetics , Chromatin/ultrastructure , Computational Biology/methods , Drosophila melanogaster/genetics , Genome, Insect/genetics , Imaging, Three-Dimensional/methods , Software , Algorithms , Animals
9.
Nat Commun ; 8: 14665, 2017 03 08.
Article in English | MEDLINE | ID: mdl-28272414

ABSTRACT

DNA-binding proteins are central regulators of chromosome organization; however, in genome-reduced bacteria their diversity is largely diminished. Whether the chromosomes of such bacteria adopt defined three-dimensional structures remains unexplored. Here we combine Hi-C and super-resolution microscopy to determine the structure of the Mycoplasma pneumoniae chromosome at a 10 kb resolution. We find a defined structure, with a global symmetry between two arms that connect opposite poles, one bearing the chromosomal Ori and the other the midpoint. Analysis of local structures at a 3 kb resolution indicates that the chromosome is organized into domains ranging from 15 to 33 kb. We provide evidence that genes within the same domain tend to be co-regulated, suggesting that chromosome organization influences transcriptional regulation, and that supercoiling regulates local organization. This study extends the current understanding of bacterial genome organization and demonstrates that a defined chromosomal structure is a universal feature of living systems.


Subject(s)
Chromosomes, Bacterial/ultrastructure , DNA, Bacterial/ultrastructure , DNA, Superhelical/ultrastructure , Gene Expression Regulation, Bacterial , Genome, Bacterial/genetics , Mycoplasma pneumoniae/genetics , Chromosome Structures , Microscopy , Molecular Conformation , Mycoplasma pneumoniae/ultrastructure , Nucleic Acid Conformation
10.
Cell Rep ; 13(9): 1855-67, 2015 Dec 01.
Article in English | MEDLINE | ID: mdl-26655901

ABSTRACT

Mating-type switching in yeast occurs through gene conversion between the MAT locus and one of two silent loci (HML or HMR) on opposite ends of the chromosome. MATa cells choose HML as template, whereas MATα cells use HMR. The recombination enhancer (RE) located on the left arm regulates this process. One long-standing hypothesis is that switching is guided by mating-type-specific and possibly RE-dependent chromosome folding. Here, we use Hi-C, 5C, and live-cell imaging to characterize the conformation of chromosome III in both mating types. We discovered a mating-type-specific conformational difference in the left arm. Deletion of a 1-kb subregion within the RE, which is not necessary during switching, abolished mating-type-dependent chromosome folding. The RE is therefore a composite element with one subregion essential for donor selection during switching and a separate region involved in modulating chromosome conformation.


Subject(s)
Chromosomes, Fungal/metabolism , Regulatory Sequences, Nucleic Acid/genetics , Saccharomyces cerevisiae/genetics , Chromatin/metabolism , Chromosomes, Fungal/chemistry , Genetic Loci , Saccharomyces cerevisiae/metabolism
11.
FEBS Lett ; 589(20 Pt A): 2987-95, 2015 Oct 07.
Article in English | MEDLINE | ID: mdl-25980604

ABSTRACT

Chromosomes are large polymer molecules composed of nucleotides. In some species, such as humans, this polymer can sum up to meters long and still be properly folded within the nuclear space of few microns in size. The exact mechanisms of how the meters long DNA is folded into the nucleus, as well as how the regulatory machinery can access it, is to a large extend still a mystery. However, and thanks to newly developed molecular, genomic and computational approaches based on the Chromosome Conformation Capture (3C) technology, we are now obtaining insight on how genomes are spatially organized. Here we review a new family of computational approaches that aim at using 3C-based data to obtain spatial restraints for modeling genomes and genomic domains.


Subject(s)
Chromosomes/ultrastructure , Genome , Models, Genetic , Animals , Chromosomes/genetics , Computer Simulation , Gene Expression Regulation , Humans , Nucleic Acid Conformation
12.
Nucleic Acids Res ; 43(7): 3465-77, 2015 Apr 20.
Article in English | MEDLINE | ID: mdl-25800747

ABSTRACT

Restraint-based modeling of genomes has been recently explored with the advent of Chromosome Conformation Capture (3C-based) experiments. We previously developed a reconstruction method to resolve the 3D architecture of both prokaryotic and eukaryotic genomes using 3C-based data. These models were congruent with fluorescent imaging validation. However, the limits of such methods have not systematically been assessed. Here we propose the first evaluation of a mean-field restraint-based reconstruction of genomes by considering diverse chromosome architectures and different levels of data noise and structural variability. The results show that: first, current scoring functions for 3D reconstruction correlate with the accuracy of the models; second, reconstructed models are robust to noise but sensitive to structural variability; third, the local structure organization of genomes, such as Topologically Associating Domains, results in more accurate models; fourth, to a certain extent, the models capture the intrinsic structural variability in the input matrices and fifth, the accuracy of the models can be a priori predicted by analyzing the properties of the interaction matrices. In summary, our work provides a systematic analysis of the limitations of a mean-field restrain-based method, which could be taken into consideration in further development of methods as well as their applications.


Subject(s)
Genome , Models, Genetic
13.
Genes Dev ; 28(19): 2151-62, 2014 Oct 01.
Article in English | MEDLINE | ID: mdl-25274727

ABSTRACT

The human genome is segmented into topologically associating domains (TADs), but the role of this conserved organization during transient changes in gene expression is not known. Here we describe the distribution of progestin-induced chromatin modifications and changes in transcriptional activity over TADs in T47D breast cancer cells. Using ChIP-seq (chromatin immunoprecipitation combined with high-throughput sequencing), Hi-C (chromosome capture followed by high-throughput sequencing), and three-dimensional (3D) modeling techniques, we found that the borders of the ∼ 2000 TADs in these cells are largely maintained after hormone treatment and that up to 20% of the TADs could be considered as discrete regulatory units where the majority of the genes are either transcriptionally activated or repressed in a coordinated fashion. The epigenetic signatures of the TADs are homogeneously modified by hormones in correlation with the transcriptional changes. Hormone-induced changes in gene activity and chromatin remodeling are accompanied by differential structural changes for activated and repressed TADs, as reflected by specific and opposite changes in the strength of intra-TAD interactions within responsive TADs. Indeed, 3D modeling of the Hi-C data suggested that the structure of TADs was modified upon treatment. The differential responses of TADs to progestins and estrogens suggest that TADs could function as "regulons" to enable spatially proximal genes to be coordinately transcribed in response to hormones.


Subject(s)
Chromatin/drug effects , Gene Expression Regulation/drug effects , Progestins/pharmacology , Cell Line, Tumor , Chromatin/chemistry , Chromatin Assembly and Disassembly/drug effects , Hormones/pharmacology , Humans
14.
Methods ; 58(3): 300-6, 2012 Nov.
Article in English | MEDLINE | ID: mdl-22522224

ABSTRACT

The three-dimensional (3D) architecture of a genome determines the spatial localization of regulatory elements and the genes they regulate. Thus, elucidating the 3D structure of a genome may result in significant insights about how genes are regulated. The current state-of-the art in experimental methods, including light microscopy and cell/molecular biology, are now able to provide detailed information on the position of genes and their interacting partners. However, such methods by themselves are not able to determine the high-resolution 3D structure of genomes or genomic domains. Here we describe a computational module of the Integrative Modeling Platform (IMP, http://www.integrativemodeling.org) that uses chromosome conformation capture data to determine the 3D architecture of genomic domains and entire genomes at unprecedented resolutions. This approach, through the visualization of looping interactions between distal regulatory elements, allows characterizing global chromatin features and their relation to gene expression. We illustrate our work by outlining the determination of the 3D architecture of the α-globin domain in the human genome.


Subject(s)
Chromatin/genetics , Chromosome Mapping , Models, Molecular , Algorithms , Calibration , Chromatin/ultrastructure , Cluster Analysis , Epistasis, Genetic , Humans , Markov Chains , Models, Genetic , Nucleic Acid Conformation , Protein Structure, Tertiary , alpha-Globins/genetics
15.
Mol Cell ; 44(2): 252-64, 2011 Oct 21.
Article in English | MEDLINE | ID: mdl-22017872

ABSTRACT

We have determined the three-dimensional (3D) architecture of the Caulobacter crescentus genome by combining genome-wide chromatin interaction detection, live-cell imaging, and computational modeling. Using chromosome conformation capture carbon copy (5C), we derive ~13 kb resolution 3D models of the Caulobacter genome. The resulting models illustrate that the genome is ellipsoidal with periodically arranged arms. The parS sites, a pair of short contiguous sequence elements known to be involved in chromosome segregation, are positioned at one pole, where they anchor the chromosome to the cell and contribute to the formation of a compact chromatin conformation. Repositioning these elements resulted in rotations of the chromosome that changed the subcellular positions of most genes. Such rotations did not lead to large-scale changes in gene expression, indicating that genome folding does not strongly affect gene regulation. Collectively, our data suggest that genome folding is globally dictated by the parS sites and chromosome segregation.


Subject(s)
Caulobacter crescentus/genetics , Chromosomes, Bacterial/physiology , Genome, Bacterial , Chromatin/physiology , Chromosome Segregation/physiology , Computer Simulation
16.
Antimicrob Agents Chemother ; 55(12): 5718-22, 2011 Dec.
Article in English | MEDLINE | ID: mdl-21930879

ABSTRACT

PA-824 is a promising drug candidate for the treatment of tuberculosis (TB). It is in phase II clinical trials as part of the first newly designed regimen containing multiple novel antituberculosis drugs (PA-824 in combination with moxifloxacin and pyrazinamide). However, given that the genes involved in resistance against PA-824 are not fully conserved in the Mycobacterium tuberculosis complex (MTBC), this regimen might not be equally effective against different MTBC genotypes. To investigate this question, we sequenced two PA-824 resistance genes (fgd1 [Rv0407] and ddn [Rv3547]) in 65 MTBC strains representing major phylogenetic lineages. The MICs of representative strains were determined using the modified proportion method in the Bactec MGIT 960 system. Our analysis revealed single-nucleotide polymorphisms in both genes that were specific either for several genotypes or for individual strains, yet none of these mutations significantly affected the PA-824 MICs (≤ 0.25 µg/ml). These results were supported by in silico modeling of the mutations identified in Fgd1. In contrast, "Mycobacterium canettii" strains displayed a higher MIC of 8 µg/ml. In conclusion, we found a large genetic diversity in PA-824 resistance genes that did not lead to elevated PA-824 MICs. In contrast, M. canettii strains had MICs that were above the plasma concentrations of PA-824 documented so far in clinical trials. As M. canettii is also intrinsically resistant against pyrazinamide, new regimens containing PA-824 and pyrazinamide might not be effective in treating M. canettii infections. This finding has implications for the design of multiple ongoing clinical trials.


Subject(s)
Antitubercular Agents/pharmacology , Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Genetic Variation , Mycobacterium tuberculosis/drug effects , Nitroimidazoles/pharmacology , Humans , Microbial Sensitivity Tests/standards , Mycobacterium tuberculosis/classification , Mycobacterium tuberculosis/genetics , Polymorphism, Single Nucleotide , Sequence Analysis, DNA
17.
Curr Opin Cell Biol ; 23(3): 325-31, 2011 Jun.
Article in English | MEDLINE | ID: mdl-21489772

ABSTRACT

Recent technological advances in the field of chromosome conformation capture are facilitating tremendous progress in the ability to map the three-dimensional (3D) organization of chromosomes at a resolution of several Kb and at the scale of complete genomes. Here we review progress in analyzing chromosome organization in human cells by building 3D models of chromatin based on comprehensive chromatin interaction datasets. We describe recent experiments that suggest that long-range interactions between active functional elements are sufficient to drive folding of local chromatin domains into compact globular states. We propose that chromatin globules are commonly formed along chromosomes, in a cell type specific pattern, as a result of frequent long-range interactions among active genes and nearby regulatory elements. Further, we speculate that increasingly longer range interactions can drive aggregation of groups of globular domains. This process would yield a compartmentalized chromosome conformation, consistent with recent observations obtained with genome-wide chromatin interaction mapping.


Subject(s)
Chromosomes/chemistry , Models, Biological , Animals , Chromatin/chemistry , Chromosome Mapping , Gene Expression , Humans , Molecular Conformation
18.
Nat Struct Mol Biol ; 18(1): 107-14, 2011 Jan.
Article in English | MEDLINE | ID: mdl-21131981

ABSTRACT

We developed a general approach that combines chromosome conformation capture carbon copy (5C) with the Integrated Modeling Platform (IMP) to generate high-resolution three-dimensional models of chromatin at the megabase scale. We applied this approach to the ENm008 domain on human chromosome 16, containing the α-globin locus, which is expressed in K562 cells and silenced in lymphoblastoid cells (GM12878). The models accurately reproduce the known looping interactions between the α-globin genes and their distal regulatory elements. Further, we find using our approach that the domain folds into a single globular conformation in GM12878 cells, whereas two globules are formed in K562 cells. The central cores of these globules are enriched for transcribed genes, whereas nontranscribed chromatin is more peripheral. We propose that globule formation represents a higher-order folding state related to clustering of transcribed genes around shared transcription machineries, as previously observed by microscopy.


Subject(s)
Chromatin/chemistry , Chromosomes, Human, Pair 16/chemistry , alpha-Globins/genetics , Chromatin/ultrastructure , Chromosomes, Human, Pair 16/metabolism , Chromosomes, Human, Pair 16/ultrastructure , Humans , In Situ Hybridization, Fluorescence , K562 Cells , Models, Molecular , Nucleic Acid Conformation , alpha-Globins/chemistry
19.
Chromosome Res ; 19(1): 25-35, 2011 Jan.
Article in English | MEDLINE | ID: mdl-21190133

ABSTRACT

The three-dimensional (3D) architecture of a genome is non-random and known to facilitate the spatial colocalization of regulatory elements with the genes they regulate. Determining the 3D structure of a genome may therefore probe an essential step in characterizing how genes are regulated. Currently, there are several experimental and theoretical approaches that aim at determining the 3D structure of genomes and genomic domains; however, approaches integrating experiments and computation to identify the most likely 3D folding of a genome at medium to high resolutions have not been widely explored. Here, we review existing methodologies and propose that the integrative modeling platform (http://www.integrativemodeling.org), a computational package developed for structurally characterizing protein assemblies, could be used for integrating diverse experimental data towards the determination of the 3D architecture of genomic domains and entire genomes at unprecedented resolution. Our approach, through the visualization of looping interactions between distal regulatory elements, will allow for the characterization of global chromatin features and their relation to gene expression. We illustrate our work by outlining the recent determination of the 3D architecture of the α-globin domain in the human genome.


Subject(s)
Computational Biology/methods , Imaging, Three-Dimensional/methods , Models, Molecular , Chromatin/ultrastructure , Chromosomes, Human/ultrastructure , Genome, Human , Humans , Models, Biological , Protein Structure, Tertiary , alpha-Globins/chemistry , alpha-Globins/genetics
20.
BMC Struct Biol ; 9: 5, 2009 Jan 30.
Article in English | MEDLINE | ID: mdl-19183478

ABSTRACT

BACKGROUND: Prediction of protein structures from their sequences is still one of the open grand challenges of computational biology. Some approaches to protein structure prediction, especially ab initio ones, rely to some extent on the prediction of residue contact maps. Residue contact map predictions have been assessed at the CASP competition for several years now. Although it has been shown that exact contact maps generally yield correct three-dimensional structures, this is true only at a relatively low resolution (3-4 A from the native structure). Another known weakness of contact maps is that they are generally predicted ab initio, that is not exploiting information about potential homologues of known structure. RESULTS: We introduce a new class of distance restraints for protein structures: multi-class distance maps. We show that C alpha trace reconstructions based on 4-class native maps are significantly better than those from residue contact maps. We then build two predictors of 4-class maps based on recursive neural networks: one ab initio, or relying on the sequence and on evolutionary information; one template-based, or in which homology information to known structures is provided as a further input. We show that virtually any level of sequence similarity to structural templates (down to less than 10%) yields more accurate 4-class maps than the ab initio predictor. We show that template-based predictions by recursive neural networks are consistently better than the best template and than a number of combinations of the best available templates. We also extract binary residue contact maps at an 8 A threshold (as per CASP assessment) from the 4-class predictors and show that the template-based version is also more accurate than the best template and consistently better than the ab initio one, down to very low levels of sequence identity to structural templates. Furthermore, we test both ab-initio and template-based 8 A predictions on the CASP7 targets using a pre-CASP7 PDB, and find that both predictors are state-of-the-art, with the template-based one far outperforming the best CASP7 systems if templates with sequence identity to the query of 10% or better are available. Although this is not the main focus of this paper we also report on reconstructions of C alpha traces based on both ab initio and template-based 4-class map predictions, showing that the latter are generally more accurate even when homology is dubious. CONCLUSION: Accurate predictions of multi-class maps may provide valuable constraints for improved ab initio and template-based prediction of protein structures, naturally incorporate multiple templates, and yield state-of-the-art binary maps. Predictions of protein structures and 8 A contact maps based on the multi-class distance map predictors described in this paper are freely available to academic users at the url http://distill.ucd.ie/.


Subject(s)
Computational Biology/methods , Models, Molecular , Neural Networks, Computer , Proteins/chemistry , Algorithms , Databases, Protein
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