Giancarlo Russo

Targeted Combinatorial Alternative Splicing Generates Brain Region-Specific Repertoires of Neurexins

Molecular diversity of surface receptors has been hypothesized to provide a mechanism for selective synaptic connectivity. Neurexins are highly diversified receptors that drive the morphological and functional differentiation of synapses. Using a single cDNA sequencing approach, we detected 1,364 unique neurexin-α and 37 neurexin-β mRNAs produced by alternative splicing of neurexin pre-mRNAs. This molecular diversity results from near-exhaustive combinatorial use of alternative splice insertions in Nrxn1α and Nrxn2α. By contrast, Nrxn3α exhibits several highly stereotyped exon selections that incorporate novel elements for posttranscriptional regulation of a subset of transcripts. Complexity of Nrxn1α repertoires correlates with the cellular complexity of neuronal tissues, and a specific subset of isoforms is enriched in a purified cell type. Our analysis defines the molecular diversity of a critical synaptic receptor and provides evidence that neurexin diversity is linked to cellular diversity in the nervous system.

The draft genome of Primula veris yields insights into the molecular basis of heterostyly

BackgroundThe flowering plant Primula veris is a common spring blooming perennial that is widely cultivated throughout Europe. This species is an established model system in the study of the genetics, evolution, and ecology of heterostylous floral polymorphisms. Despite the long history of research focused on this and related species, the continued development of this system has been restricted due the absence of genomic and transcriptomic resources.ResultsWe present here a de novo draft genome assembly of P. veris covering 301.8xa0Mb, or approximately 63% of the estimated 479.22xa0Mb genome, with an N50 contig size of 9.5 Kb, an N50 scaffold size of 164 Kb, and containing an estimated 19,507 genes. The results of a RADseq bulk segregant analysis allow for the confident identification of four genome scaffolds that are linked to the P. veris S-locus. RNAseq data from both P. veris and the closely related species P. vulgaris allow for the characterization of 113 candidate heterostyly genes that show significant floral morph-specific differential expression. One candidate gene of particular interest is a duplicated GLOBOSA homolog that may be unique to Primula (PveGLO2), and is completely silenced in L-morph flowers.ConclusionsThe P. veris genome represents the first genome assembled from a heterostylous species, and thus provides an immensely important resource for future studies focused on the evolution and genetic dissection of heterostyly. As the first genome assembled from the Primulaceae, the P. veris genome will also facilitate the expanded application of phylogenomic methods in this diverse family and the eudicots as a whole.

High‐resolution community profiling of arbuscular mycorrhizal fungi

Community analyses of arbuscular mycorrhizal fungi (AMF) using ribosomal small subunit (SSU) or internal transcribed spacer (ITS) DNA sequences often suffer from low resolution or coverage. We developed a novel sequencing based approach for a highly resolving and specific profiling of AMF communities. We took advantage of previously established AMF-specific PCR primers that amplify a c. 1.5-kb long fragment covering parts of SSU, ITS and parts of the large ribosomal subunit (LSU), and we sequenced the resulting amplicons with single molecule real-time (SMRT) sequencing. The method was applicable to soil and root samples, detected all major AMF families and successfully discriminated closely related AMF species, which would not be discernible using SSU sequences. In inoculation tests we could trace the introduced AMF inoculum at the molecular level. One of the introduced strains almost replaced the local strain(s), revealing that AMF inoculation can have a profound impact on the native community. The methodology presented offers researchers a powerful new tool for AMF community analysis because it unifies improved specificity and enhanced resolution, whereas the drawback of medium sequencing throughput appears of lesser importance for low-diversity groups such as AMF.

Post-mortem whole-exome analysis in a large sudden infant death syndrome cohort with a focus on cardiovascular and metabolic genetic diseases.

Sudden infant death syndrome (SIDS) is described as the sudden and unexplained death of an apparently healthy infant younger than one year of age. Genetic studies indicate that up to 35% of SIDS cases might be explained by familial or genetic diseases such as cardiomyopathies, ion channelopathies or metabolic disorders that remained undetected during conventional forensic autopsy procedures. Post-mortem genetic testing by using massive parallel sequencing (MPS) approaches represents an efficient and rapid tool to further investigate unexplained death cases and might help to elucidate pathogenic genetic variants and mechanisms in cases without a conclusive cause of death. In this study, we performed whole-exome sequencing (WES) in 161 European SIDS infants with focus on 192 genes associated with cardiovascular and metabolic diseases. Potentially causative variants were detected in 20% of the SIDS cases. The majority of infants had variants with likely functional effects in genes associated with channelopathies (9%), followed by cardiomyopathies (7%) and metabolic diseases (1%). Although lethal arrhythmia represents the most plausible and likely cause of death, the majority of SIDS cases still remains elusive and might be explained by a multifactorial etiology, triggered by a combination of different genetic and environmental risk factors. As WES is not substantially more expensive than a targeted sequencing approach, it represents an unbiased screening of the exome, which could help to investigate different pathogenic mechanisms within the genetically heterogeneous SIDS cohort. Additionally, re-analysis of the datasets provides the basis to identify new candidate genes in sudden infant death.

Long-term changes of bacterial and viral compositions in the intestine of a recovered Clostridium difficile patient after fecal microbiota transplantation

Fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infections (RCDIs). However, long-term effects on the patients’ gut microbiota and the role of viruses remain to be elucidated. Here, we characterized bacterial and viral microbiota in the feces of a cured RCDI patient at various time points until 4.5 yr post-FMT compared with the stool donor. Feces were subjected to DNA sequencing to characterize bacteria and double-stranded DNA (dsDNA) viruses including phages. The patients microbial communities varied over time and showed little overall similarity to the donor until 7 mo post-FMT, indicating ongoing gut microbiota adaption in this time period. After 4.5 yr, the patients bacteria attained donor-like compositions at phylum, class, and order levels with similar bacterial diversity. Differences in the bacterial communities between donor and patient after 4.5 yr were seen at lower taxonomic levels. C. difficile remained undetectable throughout the entire timespan. This demonstrated sustainable donor feces engraftment and verified long-term therapeutic success of FMT on the molecular level. Full engraftment apparently required longer than previously acknowledged, suggesting the implementation of year-long patient follow-up periods into clinical practice. The identified dsDNA viruses were mainly Caudovirales phages. Unexpectedly, sequences related to giant algae–infecting Chlorella viruses were also detected. Our findings indicate that intestinal viruses may be implicated in the establishment of gut microbiota. Therefore, virome analyses should be included in gut microbiota studies to determine the roles of phages and other viruses—such as Chlorella viruses—in human health and disease, particularly during RCDI.

SUSHI: an exquisite recipe for fully documented, reproducible and reusable NGS data analysis

BackgroundNext generation sequencing (NGS) produces massive datasets consisting of billions of reads and up to thousands of samples. Subsequent bioinformatic analysis is typically done with the help of open source tools, where each application performs a single step towards the final result. This situation leaves the bioinformaticians with the tasks to combine the tools, manage the data files and meta-information, document the analysis, and ensure reproducibility.ResultsWe present SUSHI, an agile data analysis framework that relieves bioinformaticians from the administrative challenges of their data analysis. SUSHI lets users build reproducible data analysis workflows from individual applications and manages the input data, the parameters, meta-information with user-driven semantics, and the job scripts. As distinguishing features, SUSHI provides an expert command line interface as well as a convenient web interface to run bioinformatics tools. SUSHI datasets are self-contained and self-documented on the file system. This makes them fully reproducible and ready to be shared. With the associated meta-information being formatted as plain text tables, the datasets can be readily further analyzed and interpreted outside SUSHI.ConclusionSUSHI provides an exquisite recipe for analysing NGS data. By following the SUSHI recipe, SUSHI makes data analysis straightforward and takes care of documentation and administration tasks. Thus, the user can fully dedicate his time to the analysis itself. SUSHI is suitable for use by bioinformaticians as well as life science researchers. It is targeted for, but by no means constrained to, NGS data analysis. Our SUSHI instance is in productive use and has served as data analysis interface for more than 1000 data analysis projects. SUSHI source code as well as a demo server are freely available.

Stable core virome despite variable microbiome after fecal transfer

ABSTRACT We recently described the 4.5-year time course of the enteric bacterial microbiota and virome of a patient cured from recurrent Clostridium difficile infection (rCDI) by fecal microbiota transplantation (FMT). Here, we extended the virome analyses and found the patients phage population to exhibit highly donor-similar characteristics following FMT, which remained stable for the whole period tested (up to 7 months). Moreover, the detected viral populations of donor and patient exhibited comparable diversity and richness. These findings were unexpected since enteric viromes are normally highly variable, assumed to influence the bacterial host community and change with environmental conditions. In contrast to the virome, the bacterial microbiota varied indeed for more than 7 months with ongoing dysbiosis before it reached donor similarity. Our findings that are based on sequence information and protein domain analysis seem to suggest that stable phage properties correlate with successful FMT better than the changing bacterial communities. We speculate that we here preferentially detected a stable core virome, which dominated over a variable flexible virome that may have been too heterogeneous for experimental detection or was underrepresented in the databases. It will be interesting to analyze whether the enteric virome allows predictions for the clinical outcome of FMT for rCDI and other diseases such as inflammatory bowel disease or obesity.

Candidate gene approach in genetic epidemiological studies of osteoarthritis-related pain.

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Cell Cycle Constraints and Environmental Control of Local DNA Hypomethylation in α-Proteobacteria.

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Highly sensitive, non-invasive detection of colorectal cancer mutations using single molecule, third generation sequencing

Heritable DNA methylation imprints are ubiquitous and underlie genetic variability from bacteria to humans. In microbial genomes, DNA methylation has been implicated in gene transcription, DNA replication and repair, nucleoid segregation, transposition and virulence of pathogenic strains. Despite the importance of local (hypo)methylation at specific loci, how and when these patterns are established during the cell cycle remains poorly characterized. Taking advantage of the small genomes and the synchronizability of α-proteobacteria, we discovered that conserved determinants of the cell cycle transcriptional circuitry establish specific hypomethylation patterns in the cell cycle model system Caulobacter crescentus. We used genome-wide methyl-N6-adenine (m6A-) analyses by restriction-enzyme-cleavage sequencing (REC-Seq) and single-molecule real-time (SMRT) sequencing to show that MucR, a transcriptional regulator that represses virulence and cell cycle genes in S-phase but no longer in G1-phase, occludes 5’-GANTC-3’ sequence motifs that are methylated by the DNA adenine methyltransferase CcrM. Constitutive expression of CcrM or heterologous methylases in at least two different α-proteobacteria homogenizes m6A patterns even when MucR is present and affects promoter activity. Environmental stress (phosphate limitation) can override and reconfigure local hypomethylation patterns imposed by the cell cycle circuitry that dictate when and where local hypomethylation is instated.