Biology subjects

Luis B Barreiro

Publications and source records attributed to Luis B Barreiro.

4 recordsLinked to original sources

bioRxiv2016

Genetic and transcriptional analysis of human host response to healthy gut microbiome

Many studies have demonstrated the importance of the gut microbiome in healthy and disease states. However, establishing the causality of host-microbiome interactions in humans is still challenging. Here, we describe a novel experimental system to define the transcriptional response induced by the microbiome in human cells and to shed light on the molecular mechanisms underlying host-gut microbiome interactions. In primary human colonic epithelial cells, we identified over 6,000 genes that change expression at various time points following co-culturing with the gut microbiome of a healthy individual. The differentially expressed genes are enriched for genes associated with several microbiome-related diseases, such as obesity and colorectal cancer. In addition, our experimental system allowed us to identify 87 host SNPs that show allele-specific expression in 69 genes. Furthermore, for 12 SNPs in 12 different genes, allele-specific expression is conditional on the exposure to the microbiome. Of these 12 genes, eight have been associated with diseases linked to the gut microbiome, specifically colorectal cancer, obesity and type 2 diabetes. Our study demonstrates a scalable approach to study host-gut microbiome interactions and can be used to identify putative mechanisms for the interplay between host genetics and microbiome in health and disease.

Genomics↗

bioRxiv2016

Adaptively introgressed Neandertal haplotype at the OAS locus functionally impacts innate immune responses in humans.

The 2-5 oligoadenylate synthetase (OAS) locus encodes for three OAS enzymes (OAS1-3) involved in innate immune response. This region harbors high amounts of Neandertal ancestry in non-African populations; yet, strong evidence of positive selection in the OAS region is still lacking. Here we used a broad array of selection tests in concert with neutral coalescent simulations to firmly demonstrate a signal of adaptive introgression at the OAS locus. Furthermore, we characterized the functional consequences of the Neandertal haplotype in the transcriptional regulation of OAS genes at baseline and infected conditions. We found that cells from people with the Neandertal-like haplotype express lower levels of OAS3 upon infection, as well as distinct isoforms of OAS1 and OAS2. Notably, the Neandertal-introgressed haplotype reintroduced an ancestral splice variant of OAS1 encoding a more active protein, suggesting that adaptive introgression occurred as a means to resurrect adaptive variation that had been lost outside Africa.

Evolutionary Biology↗

bioRxiv2015

Widespread shortening of 3’ untranslated regions and increased exon inclusion characterize the human macrophage response to infection

The contribution of pre-mRNA processing mechanisms to the regulation of immune responses remains poorly studied despite emerging examples of their role as regulators of immune defenses. Here, we used mRNA sequencing to quantify gene expression and isoform abundances in primary macrophages from 60 individuals, before and after infection with two live bacteria. In response to both bacteria we identified thousands of genes that significantly change isoform usage in response to infection, and found global shifts towards (i) the inclusion of cassette exons and (ii) shorter 3 UTRs. Using complementary data collected in non-human primates, we show that these features are evolutionarily conserved among primates. Finally, our results suggest that the pervasive usage of shorter 3 UTRs is a mechanism for particular genes to evade repression by immune-activated miRNAs. Collectively, our results show that dynamic changes in RNA processing play a key role in the regulation of innate immune responses.

Genomics↗

bioRxiv2015

Mycobacterial infection induces a specific human innate immune response

The innate immune system provides the first response to pathogen infection and orchestrates the activation of the adaptive immune system. Though a large component of the innate immune response is common to all infections, pathogen-specific responses have been documented as well. The innate immune response is thought to be especially critical for fighting infection with Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB). While TB can be deadly, only 5-10% of individuals infected with MTB develop active disease. The risk for disease susceptibility is, at least partly, heritable. Studies of inter-individual variation in the innate immune response to MTB infection may therefore shed light on the genetic basis for variation in susceptibility to TB. Yet, to date, we still do not know which properties of the innate immune response are specific to MTB infection and which represent a general response to pathogen infection. To begin addressing this gap, we infected macrophages with eight different bacteria, including different MTB strains and related mycobacteria, and studied the transcriptional response to infection. Although the ensued gene regulatory responses were largely consistent across the bacterial infection treatments, we were able to identify a novel subset of genes whose regulation was affected specifically by infection with mycobacteria. Genetic variants that are associated with regulatory differences in these genes should be considered candidate loci for explaining inter-individual susceptibility TB.\n\nAuthor SummaryTuberculosis (TB) is a deadly disease responsible for millions of deaths annually. It is caused by infection with Mycobacterium tuberculosis (MTB), an ancient human pathogen. Approximately a third of the worlds population is infected with MTB, yet only an estimated 5-10% of individuals will develop an active form of the disease. While this variation in TB susceptibility has been demonstrated to be heritable, we still know little about its underlying genetic basis. The genetic variation that affects TB susceptibility likely involves the innate immune system, which is our first line of defense against invading pathogens, because infection with MTB does not prevent future infections. However, we do not fully understand how the innate immune system differs in its response to MTB versus other bacteria. To investigate this further, we infected macrophages with MTB, related mycobacteria, and other bacteria, and measured how their gene expression levels changed in response. We identified a subset of genes that respond preferentially to infection with mycobacterial species. These genes provide insight into the interactions between MTB and the innate immune system and are candidate loci for explaining inter-individual susceptibility to TB.

Genomics↗