Single-cell Map of Diverse Immune Phenotypes Driven by the Tumor Microenvironment, bioRxiv, 2017-11-26
SUMMARYKnowledge of immune cell phenotypes in the tumor microenvironment is essential for understanding mechanisms of cancer progression and immunotherapy response. We created an immune map of breast cancer using single-cell RNA-seq data from 45,000 immune cells from eight breast carcinomas, as well as matched normal breast tissue, blood, and lymph node. We developed a preprocessing pipeline, SEQC, and a Bayesian clustering and normalization method, Biscuit, to address computational challenges inherent to single-cell data. Despite significant similarity between normal and tumor tissue-resident immune cells, we observed continuous tumor-specific phenotypic expansions driven by environmental cues. Analysis of paired single-cell RNA and T cell receptor (TCR) sequencing data from 27,000 additional T cells revealed the combinatorial impact of TCR utilization on phenotypic diversity. Our results support a model of continuous activation in T cells and do not comport with the macrophage polarization model in cancer, with important implications for characterizing tumor-infiltrating immune cells.
biorxiv immunology 100-200-users 20175-Formylcytosine controls nucleosome positioning through covalent histone-DNA interaction, bioRxiv, 2017-11-25
Nucleosomes are the basic unit of chromatin that ensure genome integrity and control access to the genetic information. The organization of nucleosomes is influenced by the underlying DNA sequence itself, transcription factors or other transcriptional machinery associated proteins and chromatin remodeling complexes (1–4). Herein, we show that the naturally occurring DNA modification, 5-formylcytosine (5fC) contributes to the positioning of nucleosomes. We show that the ability of 5fC to position nucleosomes in vitro is associated with the formation of covalent interactions between histone residues and 5fC in the form of Schiff bases. We demonstrate that similar interactions can occur in a cellular environment and define their specific genomic loci in mouse embryonic stem cells. Collectively, our findings identify 5fC as a determinant of nucleosomal organization in which 5fC plays a role in establishing distinct regulatory regions that are linked to gene expression Our study provides a previously unknown molecular mechanism, involving the formation of reversible-covalent bonds between chromatin and DNA that supports a molecular linkage between DNA sequence, DNA base modification and chromatin structure.
biorxiv genomics 0-100-users 2017Experimental evidence that female rhesus macaques (Macaca mulatta) perceive variation in male facial masculinity, bioRxiv, 2017-11-25
AbstractAmong many primate species, face shape is sexually dimorphic, and male facial masculinity has been proposed to influence female mate choice and male-male competition by signalling competitive ability. However, whether conspecifics pay attention to facial masculinity has only been assessed in humans. In a study of free-ranging rhesus macaques, Macaca mulatta, we used a two-alternative look-time experiment to test whether females perceive male facial masculinity. We presented 107 females with pairs of images of male faces – one with a more masculine shape and one more feminine – and recorded their looking behaviour. Females looked at the masculine face longer than at the feminine face in more trials than predicted by chance. Although there was no overall difference in average look-time between masculine and feminine faces across all trials, females looked significantly longer at masculine faces in a subset of trials for which the within-pair difference in masculinity was most pronounced. Additionally, the proportion of time subjects looked toward the masculine face increased as the within-pair difference in masculinity increased. This study provides evidence that female macaques perceive variation in male facial shape, a necessary condition for intersexual selection to operate on such a trait. It also highlights the potential impact of perceptual thresholds on look-time experiments.
biorxiv animal-behavior-and-cognition 0-100-users 2017Sensory cortex is optimised for prediction of future input, bioRxiv, 2017-11-25
Neurons in sensory cortex are tuned to diverse features in natural scenes. But what determines which features neurons become selective to? Here we explore the idea that neuronal selectivity is optimised to represent features in the recent past of sensory input that best predict immediate future inputs. We tested this hypothesis using simple feedforward neural networks, which were trained to predict the next few video or audio frames in clips of natural scenes. The networks developed receptive fields that closely matched those of real cortical neurons, including the oriented spatial tuning of primary visual cortex, the frequency selectivity of primary auditory cortex and, most notably, in their temporal tuning properties. Furthermore, the better a network predicted future inputs the more closely its receptive fields tended to resemble those in the brain. This suggests that sensory processing is optimised to extract those features with the most capacity to predict future input.Impact statementPrediction of future input explains diverse neural tuning properties in sensory cortex.
biorxiv neuroscience 0-100-users 2017Expressed Exome Capture Sequencing (EecSeq) a method for cost-effective exome sequencing for all organisms with or without genomic resources, bioRxiv, 2017-11-24
AbstractExome capture is an effective tool for surveying the genome for loci under selection. However, traditional methods require annotated genomic resources. Here, we present a method for creating cDNA probes from expressed mRNA, which are then used to enrich and capture genomic DNA for exon regions. This approach, called “EecSeq”, eliminates the need for costly probe design and synthesis. We tested EecSeq in the eastern oyster, Crassostrea virginica, using a controlled exposure experiment. Four adult oysters were heat shocked at 36° C for 1 hour along with four control oysters kept at 14° C. Stranded mRNA libraries were prepared for two individuals from each treatment and pooled. Half of the combined library was used for probe synthesis and half was sequenced to evaluate capture efficiency. Genomic DNA was extracted from all individuals, enriched via captured probes, and sequenced directly. We found that EecSeq had an average capture sensitivity of 86.8% across all known exons and had over 99.4% sensitivity for exons with detectable levels of expression in the mRNA library. For all mapped reads, over 47.9% mapped to exons and 37.0% mapped to expressed targets, which is similar to previously published exon capture studies. EecSeq displayed relatively even coverage within exons (i.e. minor “edge effects”) and even coverage across exon GC content. We discovered 5,951 SNPs with a minimum average coverage of 80X, with 3,508 SNPs appearing in exonic regions. We show that EecSeq provides comparable, if not superior, specificity and capture efficiency compared to costly, traditional methods.
biorxiv genomics 0-100-users 2017Computational haplotype recovery and long-read validation identifies novel isoforms of industrially relevant enzymes from natural microbial communities, bioRxiv, 2017-11-23
AbstractPopulation-level diversity of natural microbiomes represent a biotechnological resource for biomining, biorefining and synthetic biology but requires the recovery of the exact DNA sequence (or “haplotype”) of the genes and genomes of every individual present. Computational haplotype reconstruction is extremely difficult, complicated by environmental sequencing data (metagenomics). Current approaches cannot choose between alternative haplotype reconstructions and fail to provide biological evidence of correct predictions. To overcome this, we present Hansel and Gretel a novel probabilistic framework that reconstructs the most likely haplotypes from complex microbiomes, is robust to sequencing error and uses all available evidence from aligned reads, without altering or discarding observed variation. We provide the first formalisation of this problem and propose “metahaplome” as a definition for the set of haplotypes for any genomic region of interest within a metagenomic dataset. Finally, we demonstrate using long-read sequencing, biological evidence of novel haplotypes of industrially important enzymes computationally predicted from a natural microbiome.
biorxiv bioinformatics 0-100-users 2017