David Robelin

The sheep genome illuminates biology of the rumen and lipid metabolism

A genome for ewe and ewe Sheep-specific genetic changes underlie differences in lipid metabolism between sheep and other mammals, and may have contributed to the production of wool. Jiang et al. sequenced the genome of two Texel sheep, a breed that produces high-value meat, milk, and wool. The genome information will provide an important resource for livestock production and aid in the understanding of mammalian evolution. Science, this issue p. 1168 A genomic analysis of sheep explains specializations in digestive system physiology and wool production. Sheep (Ovis aries) are a major source of meat, milk, and fiber in the form of wool and represent a distinct class of animals that have a specialized digestive organ, the rumen, that carries out the initial digestion of plant material. We have developed and analyzed a high-quality reference sheep genome and transcriptomes from 40 different tissues. We identified highly expressed genes encoding keratin cross-linking proteins associated with rumen evolution. We also identified genes involved in lipid metabolism that had been amplified and/or had altered tissue expression patterns. This may be in response to changes in the barrier lipids of the skin, an interaction between lipid metabolism and wool synthesis, and an increased role of volatile fatty acids in ruminants compared with nonruminant animals.

Pool-hmm: a Python program for estimating the allele frequency spectrum and detecting selective sweeps from next generation sequencing of pooled samples

Due to its cost effectiveness, next generation sequencing of pools of individuals (Pool‐Seq) is becoming a popular strategy for genome‐wide estimation of allele frequencies in population samples. As the allele frequency spectrum provides information about past episodes of selection, Pool‐seq is also a promising design for genomic scans for selection. However, no software tool has yet been developed for selection scans based on Pool‐Seq data. We introduce Pool‐hmm, a Python program for the estimation of allele frequencies and the detection of selective sweeps in a Pool‐Seq sample. Pool‐hmm includes several options that allow a flexible analysis of Pool‐Seq data, and can be run in parallel on several processors. Source code and documentation for Pool‐hmm is freely available at https://qgsp.jouy.inra.fr/.

Transcriptomic and nuclear architecture of immune cells after LPS activation

Changes in the nuclear positioning of specific genes, depending on their expression status, have been observed in a large diversity of physiological processes. However, gene position is poorly documented for immune cells which have been subjected to activation following bacterial infection. Using a pig model, we focused our study on monocyte-derived macrophages and neutrophils, as they are the first lines of defence against pathogens. We examined whether changes in gene expression due to LPS activation imply that genes have repositioned in the nuclear space. We first performed a transcriptomic analysis to identify the differentially expressed genes and then analysed the networks involved during lypopolysaccharide/interferon gamma activation in monocyte-derived macrophages. This allowed us to select four up-regulated (IL1β, IL8, CXCL10 and TNFα) and four down-regulated (VIM, LGALS3, TUBA3 and IGF2) genes. Their expression statuses were verified by quantitative real-time RT-PCR before studying their behaviour in the nuclear space during macrophage activation by means of 3D fluorescence in situ hybridization. No global correlation was found between gene activity and radial positioning. Only TNFα belonging to the highly transcribed MHC region on chromosome 7 became more peripherally localized in relation to the less decondensed state of its chromosome territory (CT) in activated macrophages. The analysis of gene positioning towards their CT revealed that IL8 increases significantly its tendency to be outside its CT during the activation process. In addition, the gene to CT edge distances increase for the three up-regulated genes (IL8, CXCL10 and TNFα) among the four analysed. Contrarily, the four down-regulated genes did not change their position. The analysis of gene behaviour towards their CT was extended to include neutrophils for three (TNFα, IL8 and IL1β) up- and two (IGF2 and TUBA3) down-regulated genes, and similar results were obtained. The analysis was completed by studying the four up-regulated genes in fibroblasts, not involved in immune response. Our data suggest that relocation in the nuclear space of genes that are differentially expressed in activated immune cells is gene and cell type specific but also closely linked to the entire up-regulation status of their chromosomal regions.

Nuclear architecture of resting and LPS-stimulated porcine neutrophils by 3D FISH

Neutrophils are essential components of the innate immune system due to their ability to kill and phagocytose invading microbes. They possess a lobulated nucleus and are capable of extensive and complex changes in response to bacterial stimulation. The aim of our study was to investigate whether the 3D nuclear organization of porcine neutrophils was modified upon stimulation. The organization of centromeres, telomeres, and chromosome territories (chromosomes 2, 3, 7, 8, 12, 13, and 17) was studied on structurally preserved nuclei using 3D fluorescence in situ hybridization, confocal microscopy, and image analysis. By differential labeling of centromeres of acrocentric and metacentric/submetacentric chromosomes, we showed that centromeres associated to form chromocenters but did so preferentially between chromosomes with the same morphology. Upon activation, some of these chromocenters dispersed. Telomeres were also found to form clusters, but their number remained unchanged in lipopolysaccharide-stimulated neutrophils. The analysis of the position of chromocenters and telomere clusters showed a more internal location of the latter compared to the former. The analysis of chromosome territories revealed that homologs were distributed randomly among lobes whatever the cell’s status. The volume of these territories was not proportional to chromosome length, and some chromosomes (chr 3, 12, 13, and 17) were more prone to decondensation when neutrophils were stimulated. Thus, our study demonstrated that activation of neutrophils resulted in several modifications of their nuclear architecture: a decrease in the number of non-acrocentric chromocenters and the decondensation of several chromosomes.

Accounting for Linkage Disequilibrium in genome scans for selection without individual genotypes : the local score approach

Detecting genomic footprints of selection is an important step in the understanding of evolution. Accounting for linkage disequilibrium in genome scans increases detection power, but haplotype‐based methods require individual genotypes and are not applicable on pool‐sequenced samples. We propose to take advantage of the local score approach to account for linkage disequilibrium in genome scans for selection, cumulating (possibly small) signals from single markers over a genomic segment, to clearly pinpoint a selection signal. Using computer simulations, we demonstrate that this approach detects selection with higher power than several state‐of‐the‐art single‐marker, windowing or haplotype‐based approaches. We illustrate this on two benchmark data sets including individual genotypes, for which we obtain similar results with the local score and one haplotype‐based approach. Finally, we apply the local score approach to Pool‐Seq data obtained from a divergent selection experiment on behaviour in quail and obtain precise and biologically coherent selection signals: while competing methods fail to highlight any clear selection signature, our method detects several regions involving genes known to act on social responsiveness or autistic traits. Although we focus here on the detection of positive selection from multiple population data, the local score approach is general and can be applied to other genome scans for selection or other genomewide analyses such as GWAS.

Livestock genome annotation: transcriptome and chromatin structure profiling in cattle, goat, chicken and pig.

Background Functional annotation of livestock genomes is a critical step to decipher the genotype-to-phenotype relationship underlying complex traits. As part of the Functional Annotation of Animal Genomes (FAANG) action, the FR-AgENCODE project aims at profiling the landscape of transcription (RNA-seq) and chromatin accessibility and conformation (ATAC-seq and Hi-C) in four livestock species representing ruminants (cattle, goat), monogastrics (pig) and birds (chicken), using three target samples related to metabolism (liver) and immunity (CD4+ and CD8+ T cells). Results Standardized protocols were applied to produce transcriptome and chromatin datasets for the four species. RNA-seq assays considerably extended the available catalog of protein-coding and non-coding transcripts. Gene expression profiles were consistent with known metabolic/immune functions and revealed differentially expressed transcripts with unknown function, including new lncRNAs in syntenic regions. The majority of ATAC-seq peaks of chromatin accessibility mapped to putative regulatory regions, with an enrichment of predicted transcription factor binding sites in differentially accessible peaks. Hi-C provided the first set of genome-wide maps of three-dimensional interactions across livestock and showed consistency with results from gene expression and chromatin accessibility in topological compartments of the genomes. Conclusions We report the first multi-species and multi-assay genome annotation results obtained by a FAANG pilot project. The global consistency between gene expression and chromatin structure data in these four livestock species confirms previous findings in model animals. Overall, these results emphasize the value of FAANG for research on domesticated animals and strengthen the importance of future meta-analyses of the reference datasets being generated by this community on different species.Abstract Background Functional annotation of livestock genomes is a critical step to decipher the genotype-to-phenotype relationship underlying complex traits. As part of the Functional Annotation of Animal Genomes (FAANG) action, the FR-AgENCODE project (http://www.fragencode.org) aimed to profile the landscape of transcription (RNA-seq), chromatin accessibility (ATAC-seq) and conformation (Hi-C) in four livestock species representing ruminants (cattle, goat), monogastrics (pig) and birds (chicken), using three target samples related to metabolism (liver) and immunity (CD4+ and CD8+ T cells). Results RNA-seq assays considerably extended the available catalog of annotated transcripts and identified differentially expressed genes with unknown function, including new syntenic lncRNAs. ATAC-seq highlighted an enrichment for transcription factor binding sites in differentially accessible regions of the chromatin. Comparative analyses revealed a core set of conserved regulatory regions across species. Topologically Associating Domains (TADs) and epigenetic A/B compartments annotated from Hi-C data were consistent with RNA-seq and ATAC-seq data. Multi-species comparisons showed that conserved TAD boundaries had stronger insulation properties than species-specific ones and that the genomic distribution of orthologous genes in A/B compartments was significantly conserved across species. Conclusions We report the first multi-species and multi-assay genome annotation results obtained by a FAANG project. Beyond the generation of reference annotations and the confirmation of previous findings on model animals, the integrative analysis of data from multiple assays and species sheds a new light on the multi-scale selective pressure shaping genome organization from birds to mammals. Overall, these results emphasize the value of FAANG for research on domesticated animals and reinforces the importance of future meta-analyses of the reference datasets being generated by this community on different species.

3D nuclear organization of the CMH complex in control and LPS-activated porcine macrophages

Chromosomal abnormalities in secondary bovine oocytes matured in vitro up to 48 hours Abstract Chromosomal abnormalities in secondary bovine oocytes matured in vitro up to 48 hours. 21st International Colloquium on Animal Cytogenetics and Gene Mapping Rubessa M., Pauciullo A., Peretti V., Iannuzzi L., Ramunno L., Di Berardino D.Edited by: L. Iannuzzi, A. Perucatti, A. Iannuzzi, A. Pauciullo, V. Genualdo, D. Incarnato, L. Keller (CNRISPAAM, Naples, Italy)Sister Chromatid exchange (SCE) test in river buffalo cells treated with Furocoumarins. / Iannuzzi A.; Perucatti A.; Genualdo V.; Pauciullo A.; Pucciarelli L.; Incarnato D.; Melis R.; Porqueddu C.; Marchetti M.; Iannuzzi L.. In: CHROMOSOME RESEARCH. ISSN 0967-3849. 22(2014), pp. 421-421. Original Citation: Sister Chromatid exchange (SCE) test in river buffalo cells treated with Furocoumarins.Comparative FISH-mapping of TNF, STAT5A and MNTR1A fecundity genes on river buffalo, cattle, sheep and goat. / Iannuzzi A.; Perucatti A.; Pauciullo A.; Genualdo V.; Incarnato D.; Pucciarelli L.; De Lorenzi L.; Parma P.; Iannuzzi L.. In: CHROMOSOME RESEARCH. ISSN 0967-3849. 22(2014), pp. 418-418. Original Citation: Comparative FISH-mapping of TNF, STAT5A and MNTR1A fecundity genes on river buffalo, cattle, sheep and goat.Multicolor FISH with 10 specific painting probes for the rapid identification of the sub-metacentric river buffalo autosomes (Bubalus bubalis, 2n=50) / Pauciullo A.; Perucatti A.; Iannuzzi A.; Incarnato D.; Genualdo V.; Pucciarelli L.; Di Berardino D.; Iannuzzi L.. In: CHROMOSOME RESEARCH. ISSN 0967-3849. 22(2014), pp. 410-410. Original Citation: Multicolor FISH with 10 specific painting probes for the rapid identification of the sub-metacentric river buffalo autosomes (Bubalus bubalis, 2n=50)