Biology subjects

Gloudemans, M. J.

Publications and source records attributed to Gloudemans, M. J..

7 recordsLinked to original sources

bioRxiv2023

Transcriptomics and chromatin accessibility in multiple African population samples

Mapping the functional human genome and impact of genetic variants is often limited to European-descendent population samples. To aid in overcoming this limitation, we measured gene expression using RNA sequencing in lymphoblastoid cell lines (LCLs) from 599 individuals from six African populations to identify novel transcripts including those not represented in the hg38 reference genome. We used whole genomes from the 1000 Genomes Project and 164 Maasai individuals to identify 8,881 expression and 6,949 splicing quantitative trait loci (eQTLs/sQTLs), and 2,611 structural variants associated with gene expression (SV-eQTLs). We further profiled chromatin accessibility using ATAC-Seq in a subset of 100 representative individuals, to identity chromatin accessibility quantitative trait loci (caQTLs) and allele-specific chromatin accessibility, and provide predictions for the functional effect of 78.9 million variants on chromatin accessibility. Using this map of eQTLs and caQTLs we fine-mapped GWAS signals for a range of complex diseases. Combined, this work expands global functional genomic data to identify novel transcripts, functional elements and variants, understand population genetic history of molecular quantitative trait loci, and further resolve the genetic basis of multiple human traits and disease.

genomics↗

bioRxiv2022

CROP-Seq: a single-cell CRISPRi platform for characterizing candidate genes relevant to metabolic disorders in human adipocytes

ObjectiveCROP-Seq combines gene silencing using CRISPR interference (CRISPRi) with single-cell RNA sequencing (scRNA-Seq) to conduct a functional reverse genetic screen of novel gene targets associated with adipocyte differentiation or function, with single-cell transcriptomes as the readout. MethodsWe created a human preadipocyte SGBS cell line with stable expression of KRAB-dCas9 for CRISPRi-mediated gene knock-down. This line was transduced with a lentiviral library of sgRNAs targeting 6 genes of interest (3 sgRNAs / gene, 18 sgRNAs), 6 positive control genes (3 sgRNAs / gene, 18 sgRNAs), and non-targeting control sgRNAs (4 sgRNAs). Transduced cells were selected and differentiated, and individual cells were captured using microfluidics at day 0, 4 and 8 of adipogenic differentiation. Next, expression and sgRNA libraries were created and sequenced. Bioinformatic analysis of resulting scRNA-Seq expression data was used to determine the effects of gene knock-down and the dysregulated pathways, and to predict cellular phenotypes. ResultsSingle-cell transcriptomes obtained from SGBS cells following CRISPRi recapitulate different states of differentiation from preadipocytes to adipocytes. We confirmed successful knock-down of targeted genes. Transcriptome-wide changes were observed for all targeted genes, with over 400 differentially expressed genes identified per gene at least at one timepoint. Knock-down of known adipogenesis regulators PPARG and CEBPB inhibited adipogenesis. Gene set enrichment analyses revealed molecular processes for adipose tissue differentiation and function for novel genes. MAFF knock-down led to a downregulation of transcriptional response to proinflammatory cytokine TNF- in preadipocytes. TIPARP knock-down resulted in an increase in the expression of a beiging marker UCP1 at D8 of adipogenesis. ConclusionsThe CROP-Seq system in SGBS cells can determine the consequences of target gene knock-down at the transcriptome level. This powerful, hypothesis-free tool can identify novel regulators of adipogenesis, preadipocyte and adipocyte function associated with metabolic disease. HighlightsO_LICRISPR interference screen coupled with single-cell RNA sequencing (CROP-Seq) C_LIO_LIParallel screening of 12 genes in human SGBS adipocytes and preadipocytes C_LIO_LIUncovered novel regulators of adipogenesis and adipocyte function C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/497796v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@1ee34b6org.highwire.dtl.DTLVardef@1c6ba8aorg.highwire.dtl.DTLVardef@fa89org.highwire.dtl.DTLVardef@403966_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2021

An integrated approach to identify environmental modulators of genetic risk factors for complex traits

Complex traits and diseases can be influenced by both genetics and environment. However, given the large number of environmental stimuli and power challenges for gene-by-environment testing, it remains a critical challenge to identify and prioritize specific disease-relevant environmental exposures. We propose a novel framework for leveraging signals from transcriptional responses to environmental perturbations to identify disease-relevant perturbations that can modulate genetic risk for complex traits and inform the functions of genetic variants associated with complex traits. We perturbed human skeletal muscle, fat, and liver relevant cell lines with 21 perturbations affecting insulin resistance, glucose homeostasis, and metabolic regulation in humans and identified thousands of environmentally responsive genes. By combining these data with GWAS from 31 distinct polygenic traits, we show that heritability of multiple traits is enriched in regions surrounding genes responsive to specific perturbations and, further, that environmentally responsive genes are enriched for associations with specific diseases and phenotypes from the GWAS catalogue. Overall, we demonstrate the advantages of large-scale characterization of transcriptional changes in diversely stimulated and pathologically relevant cells to identify disease-relevant perturbations.

genomics↗

bioRxiv2020

Single-cell epigenomic identification of inherited risk loci in Alzheimer's and Parkinson's disease

Genome-wide association studies (GWAS) have identified thousands of variants associated with disease phenotypes. However, the majority of these variants do not alter coding sequences, making it difficult to assign their function. To this end, we present a multi-omic epigenetic atlas of the adult human brain through profiling of the chromatin accessibility landscapes and three-dimensional chromatin interactions of seven brain regions across a cohort of 39 cognitively healthy individuals. Single-cell chromatin accessibility profiling of 70,631 cells from six of these brain regions identifies 24 distinct cell clusters and 359,022 cell type-specific regulatory elements, capturing the regulatory diversity of the adult brain. We develop a machine learning classifier to integrate this multi-omic framework and predict dozens of functional single nucleotide polymorphisms (SNPs), nominating gene and cellular targets for previously orphaned GWAS loci. These predictions both inform well-studied disease-relevant genes, such as BIN1 in microglia for Alzheimers disease (AD) and reveal novel gene-disease associations, such as STAB1 in microglia and MAL in oligodendrocytes for Parkinsons disease (PD). Moreover, we dissect the complex inverted haplotype of the MAPT (encoding tau) PD risk locus, identifying ectopic enhancer-gene contacts in neurons that increase MAPT expression and may mediate this disease association. This work greatly expands our understanding of inherited variation in AD and PD and provides a roadmap for the epigenomic dissection of noncoding regulatory variation in disease.

genomics↗

bioRxiv2019

Systematic assessment of regulatory effects of human disease variants in pluripotent cells

Identifying regulatory genetic effects in pluripotent cells provides important insights into disease variants with potentially transient or developmental origins. Combining existing and newly-generated data, we characterized 1,367 iPSC lines from 948 unique donors, collectively analyzed within the \"Integrated iPSC QTL\" (i2QTL) Consortium. The sample size of our study allowed us to derive the most comprehensive map of quantitative trait loci (QTL) in pluripotent human cells to date. We mapped the effects of nearby common genetic variants on five expression phenotypes, identifying cis-QTL at gene-, exon-level and transcript-, splicing-, alternative polyadenylation-ratio (APA) for a total of 18,556 genes. For gene-level, we further quantified the effects of rare and singleton variants, and the effect of distal variants that act in trans (trans-eQTL), which we replicated in independent samples. Our data are a valuable community resource, uncovering novel regulatory effects that have not previously been described in differentiated cells and tissues. Building on this regulatory map, we functionally explore GWAS signals for over 4,336 trait loci, finding evidence for colocalization with common and rare iPSC QTL for traits such as height and BMI, and diseases, such as cancer and coronary artery disease.

genomics↗

bioRxiv2019

Genetic dysregulation of gene expression and splicing during a ten-year period of human aging

Molecular and cellular changes are intrinsic to aging and age-related diseases. Prior cross-sectional studies have investigated the combined effects of age and genetics on gene expression and alternative splicing; however, there has been no long-term, longitudinal characterization of these molecular changes, especially in older age. We performed RNA sequencing in whole-blood from the same individuals from the PIVUS study at ages 70 and 80 to quantify how gene expression, alternative splicing, and their genetic regulation are altered during this 10-year period of advanced aging. We observe that individuals are more similar to their own expression profiles later in life than profiles of other individuals their own age; 93% of samples cluster with their own measurement at another age, and there is a strong correlation of genetic effects on expression between the two ages (median{rho} G = 0.96). Despite this, we identify 1,291 and 294 genes differentially expressed and alternatively spliced with age, as well as 529 genes with outlying individual trajectories of aging. Further, 7.8% and 9.6% of tested genes show a reduction in genetic associations with expression and alternative splicing in older age, with impacted genes enriched in DNA repair pathways. Together these findings indicate that, although gene expression and alternative splicing and their genetic regulation are mostly stable late in life, a small subset of genes is dynamic and is characterized by changes in expression and splicing and a reduction in genetic regulation.

genomics↗

bioRxiv2018

Ocular disease mechanisms elucidated by genetics of human fetal retinal pigment epithelium gene expression

The eye is an intricate organ with limited representation in large-scale functional genomics datasets. The retinal pigment epithelium (RPE) serves vital roles in ocular development and retinal homeostasis. We interrogated the genetics of gene expression of cultured human fetal RPE (fRPE) cells under two metabolic conditions. Genes with disproportionately high fRPE expression are enriched for genes related to inherited ocular diseases. Variants near these fRPE-selective genes explain a larger fraction of risk for both age-related macular degeneration (AMD) and myopia than variants near genes enriched in 53 other human tissues. Increased mitochondrial oxidation of glutamine by fRPE promoted expression of lipid synthesis genes implicated in AMD. Expression and splice quantitative trait loci (e/sQTL) analysis revealed shared and metabolic condition-specific loci of each type and several eQTL not previously described in any tissue. Fine mapping of fRPE e/sQTL across AMD and myopia genome-wide association data suggests new candidate genes, and mechanisms by which the same common variant of RDH5 contributes to both increased AMD risk and decreased myopia risk. Our study highlights the unique transcriptomic characteristics of fRPE and provides a resource to connect e/sQTL in a critical ocular cell type to monogenic and complex eye disorders.

genomics↗