Characterisation of the global transcriptional response to heat shock and the impact of individual genetic variation

Abstract Background The heat shock transcriptional response is essential to effective cellular function under stress. This is a highly heritable trait but the nature and extent of inter-individual variation in heat shock response remains unresolved. Methods We determined global transcription profiles of the heat shock response for a panel of lymphoblastoid cell lines established from 60 founder individuals in the Yoruba HapMap population. We explore the observed differentially expressed gene sets following heat shock, establishing functional annotations, underlying networks and nodal genes involving heat shock factor 1 recruitment. We define a multivariate phenotype for the global transcriptional response to heat shock using partial least squares regression and map this quantitative trait to associated genetic variation in search of the major genomic modulators. Results A comprehensive dataset of differentially expressed genes following heat shock in humans is presented. We identify nodal genes downstream of heat shock factor 1 in this gene set, notably involving ubiquitin C and small ubiquitin-like modifiers together with transcription factors. We dissect a multivariate phenotype for the global heat shock response which reveals distinct clustering of individuals in terms of variance of the heat shock response and involves differential expression of genes involved in DNA replication and cell division in some individuals. We find evidence of genetic associations for this multivariate response phenotype that involves trans effects modulating expression of genes following heat shock, including HSF1 and UBQLN1. Conclusion This study defines gene expression following heat shock for a cohort of individuals, establishing insights into the biology of the heat shock response and hypotheses for how variation in this may be modulated by underlying genetic diversity

Genetic determinants of HSP70 gene expression following heat shock

The regulation of heat shock protein expression is of significant physiological and pathophysiological significance. Here we show that genetic diversity is an important determinant of heat shock protein 70 expression involving local, likely cis-acting, polymorphisms. We define DNA sequence variation for the highly homologous HSPA1A and HSPA1B genes in the major histocompatibility complex on chromosome 6p21 and establish quantitative and specific assays for determining transcript abundance. We show for lymphoblastoid cell lines established from individuals of African ancestry that following heat shock, expression of HSPA1B is associated with rs400547 (P 3.88 × 10−8) and linked single nucleotide polymorphisms (SNPs) located 62–93 kb telomeric to HSPA1B. This association was found to explain 31 and 29% of the variance in HSPA1B expression following heat shock or in resting cells, respectively. The associated SNPs show marked variation in minor allele frequency among populations, being more common in individuals of African ancestry, and are located in a region showing population-specific haplotypic block structure. The work illustrates how analysis of a heritable induced expression phenotype can be highly informative in defining functionally important genetic variation

Expression of the Multiple Sclerosis-Associated MHC Class II Allele HLA-DRB1*1501 Is Regulated by Vitamin D

Multiple sclerosis (MS) is a complex trait in which allelic variation in the MHC class II region exerts the single strongest effect on genetic risk. Epidemiological data in MS provide strong evidence that environmental factors act at a population level to influence the unusual geographical distribution of this disease. Growing evidence implicates sunlight or vitamin D as a key environmental factor in aetiology. We hypothesised that this environmental candidate might interact with inherited factors and sought responsive regulatory elements in the MHC class II region. Sequence analysis localised a single MHC vitamin D response element (VDRE) to the promoter region of HLA-DRB1. Sequencing of this promoter in greater than 1,000 chromosomes from HLA-DRB1 homozygotes showed absolute conservation of this putative VDRE on HLA-DRB1*15 haplotypes. In contrast, there was striking variation among non–MS-associated haplotypes. Electrophoretic mobility shift assays showed specific recruitment of vitamin D receptor to the VDRE in the HLA-DRB1*15 promoter, confirmed by chromatin immunoprecipitation experiments using lymphoblastoid cells homozygous for HLA-DRB1*15. Transient transfection using a luciferase reporter assay showed a functional role for this VDRE. B cells transiently transfected with the HLA-DRB1*15 gene promoter showed increased expression on stimulation with 1,25-dihydroxyvitamin D3 (P = 0.002) that was lost both on deletion of the VDRE or with the homologous “VDRE” sequence found in non–MS-associated HLA-DRB1 haplotypes. Flow cytometric analysis showed a specific increase in the cell surface expression of HLA-DRB1 upon addition of vitamin D only in HLA-DRB1*15 bearing lymphoblastoid cells. This study further implicates vitamin D as a strong environmental candidate in MS by demonstrating direct functional interaction with the major locus determining genetic susceptibility. These findings support a connection between the main epidemiological and genetic features of this disease with major practical implications for studies of disease mechanism and prevention

An immune dysfunction score for stratification of patients with acute infection based on whole-blood gene expression

Dysregulated host responses to infection can lead to organ dysfunction and sepsis, causing millions of global deaths each year. To alleviate this burden, improved prognostication and biomarkers of response are urgently needed. We investigated the use of whole-blood transcriptomics for stratification of patients with severe infection by integrating data from 3149 samples from patients with sepsis due to community-acquired pneumonia or fecal peritonitis admitted to intensive care and healthy individuals into a gene expression reference map. We used this map to derive a quantitative sepsis response signature (SRSq) score reflective of immune dysfunction and predictive of clinical outcomes, which can be estimated using a 7- or 12-gene signature. Last, we built a machine learning framework, SepstratifieR, to deploy SRSq in adult and pediatric bacterial and viral sepsis, H1N1 influenza, and COVID-19, demonstrating clinically relevant stratification across diseases and revealing some of the physiological alterations linking immune dysregulation to mortality. Our method enables early identification of individuals with dysfunctional immune profiles, bringing us closer to precision medicine in infection.peer-reviewe

Effects of single nucleotide polymorphisms on the expression of HSP70 genes, HSPA1A and HSPA1B

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Effects of single nucleotide polymorphisms on the expression of HSP70 genes, HSPA1A and HSPA1B

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Genetic determinants of HSP70 gene expression following heat shock

doi:10.1093/hmg/ddq41

Additional file 3: Table S1. of Characterisation of the global transcriptional response to heat shock and the impact of individual genetic variation

Differentially expressed genes following heat shock. Differentially expressed genes for a panel of 43 LCLs exposed to heat shock (42 °C for 1 h, 6 h recovery) and assayed by microarray are shown following limma analysis (FC >1.2, FDR <0.01). Table S2. GO categories enriched for upregulated genes. GO categories for differentially expressed genes upregulated following heat shock in LCLs are shown. Numbers of significant and expected genes shown, together with p values (Fisher’s exact test). Table S3. GO categories enriched for downregulated genes. GO categories for differentially expressed genes downregulated following heat shock in LCLs are shown. Numbers of significant and expected genes shown, together with p values (Fisher’s exact test). Table S4. Network analysis following heat shock. Networks identified on IPA analysis of differentially expressed genes (FC >1.2, FDR <0.01) following heat shock. Table S5. Genes with newly established links to heat shock response. Genes listed together with FC and FDR following heat shock, and p value for presence of the heat shock binding motif. Table S6. Summary of HSF-binding evidence for the promoters of novel and established heat shock response genes. Presence of ChIP-seq peak for HSF1 or HSF2 and HSF1 motif indicated in relation to heat shock genes. Table S7. Differential gene expression between PLS clusters. Differential gene expression between samples assigned to PLS cluster 1 and 2 as assessed by limma analysis is shown for all assayed probes. Table S8. GO categories enriched for genes with increased expression in cluster 2. GO categories for genes differentially expressed between PLS clusters. Categories enriched for genes with increased expression in cluster 2 are shown. Numbers of significant and expected genes shown, together with p values (Fisher’s exact test). Table S9. GO categories enriched for genes with increased expression in cluster 1. GO categories for genes differentially expressed between PLS clusters. Categories enriched for genes with increased expression in cluster 1 are shown. Numbers of significant and expected genes shown, together with p values (Fisher’s exact test). (XLSX 4875 kb

Additional file 1: Figure S1. of Characterisation of the global transcriptional response to heat shock and the impact of individual genetic variation

PCA plot of ComBat corrected gene expression. PCA plot for gene expression in LCLs following heat shock post microarray processing and QC with individual lines coloured by BeadChIP. (PDF 166 kb