Biology subjects

Freimer, J. W.

Publications and source records attributed to Freimer, J. W..

4 recordsLinked to original sources

bioRxiv2023

Gene regulatory network inference from CRISPR perturbations in primary CD4+ T cells elucidates the genomic basis of immune disease

The effects of genetic variation on complex traits act mainly through changes in gene regulation. Although many genetic variants have been linked to target genes in cis, the trans-regulatory cascade mediating their effects remains largely uncharacterized. Mapping trans-regulators based on natural genetic variation, including eQTL mapping, has been challenging due to small effects. Experimental perturbation approaches offer a complementary and powerful approach to mapping trans-regulators. We used CRISPR knockouts of 84 genes in primary CD4+ T cells to perturb an immune cell gene network, targeting both inborn error of immunity (IEI) disease transcription factors (TFs) and background TFs matched in constraint and expression level, but without a known immune disease association. We developed a novel Bayesian structure learning method called Linear Latent Causal Bayes (LLCB) to estimate the gene regulatory network from perturbation data and observed 211 directed edges among the genes which could not be detected in existing CD4+ trans-eQTL data. We used LLCB to characterize the differences between the IEI and background TFs, finding that the gene groups were highly interconnected, but that IEI TFs were much more likely to regulate immune cell specific pathways and immune GWAS genes. We further characterized nine coherent gene programs based on downstream effects of the TFs and linked these modules to regulation of GWAS genes, finding that canonical JAK-STAT family members are regulated by KMT2A, a global epigenetic regulator. These analyses reveal the trans-regulatory cascade from upstream epigenetic regulator to intermediate TFs to downstream effector cytokines and elucidate the logic linking immune GWAS genes to key signaling pathways.

genomics↗

bioRxiv2021

CRISPR activation and interference screens in primary human T cells decode cytokine regulation

The pathways that regulate cytokine responses in T cells are disrupted in autoimmunity, immune deficiencies, and cancer, and include immunotherapy targets. Systematic discovery of cytokine regulators requires both loss-of-function and gain-of-function studies, which have been challenging in primary human cells. We now have accomplished genome-wide pooled CRISPR activation (CRISPRa) and CRISPR interference (CRISPRi) screens in primary human T cells to map gene networks controlling Interleukin-2 and Interferon-{gamma} production. Arrayed CRISPRa confirmed key hits and enabled multiplexed T cell secretome characterization, revealing reshaped cytokine responses driven by individual regulators. CRISPRa uncovered genes not canonically expressed in T cells, including the transcription factor FOXQ1, whose overexpression promoted the expression of most cytokines, while selectively dampening T helper 2 (Th2) cytokines. Paired CRISPRa and CRISPRi screens reveal signaling components that tune critical immune cell functions, which could inform design of future immunotherapies.

immunology↗

bioRxiv2021

Systematic discovery and perturbation of regulatory genes in human T cells reveals the architecture of immune networks

Complex gene regulatory networks ensure that important genes are expressed at precise levels. When gene expression is sufficiently perturbed it can lead to disease. To understand how gene expression disruptions percolate through a network, we must first map connections between regulatory genes and their downstream targets. However, we lack comprehensive knowledge of the upstream regulators of most genes. Here we developed an approach for systematic discovery of upstream regulators of critical immune factors - IL2RA, IL-2, and CTLA4 - in primary human T cells. Then, we mapped the network of these regulators target genes and enhancers using CRISPR perturbations, RNA-Seq, and ATAC-Seq. These regulators form densely interconnected networks with extensive feedback loops. Furthermore, this network is highly enriched for immune-associated disease variants and genes. These results provide insight into how immune-associated disease genes are regulated in T cells and broader principles about the structure of human gene regulatory networks. HighlightsO_LIA systematic approach to identify upstream regulators of key immune genes in primary human cells C_LIO_LIComprehensive RNA-Seq and ATAC-Seq perturbation maps after KO of individual discovered regulators C_LIO_LIAnalysis uncovers a highly interconnected regulatory network of enhancers and genes in T cells C_LIO_LIThis network is highly enriched for immune disease variants and genes shedding light on the trans-regulatory connections among key immune genes in health and disease C_LI

genomics↗

bioRxiv2018

Decoupling the impact of microRNAs on translational repression versus RNA degradation in embryonic stem cells

Translation and mRNA degradation are intimately connected, yet the mechanisms that regulate them are not fully understood. Here we studied the link between translation and mRNA stability in embryonic stem cells (ESCs). Transcripts showed a wide range of stabilities, which correlated with their translation levels. The protein DHH1 links translation to mRNA stability in yeast; however loss of the mammalian homolog, DDX6, in ESCs did not disrupt the correlation across transcripts. Instead, the loss of DDX6 led to upregulated translation of microRNA targets, without concurrent changes in mRNA stability. The Ddx6 knockout cells were phenotypically and molecularly similar to cells lacking all microRNAs (Dgcr8 knockout ESCs). These data show that the loss of DDX6 can separate the two canonical functions of microRNAs: translational repression and transcript destabilization. Furthermore, these data uncover a central role for translational repression independent of transcript destabilization in defining the downstream consequences of microRNA loss.

genetics↗