Areas of Research
Epigenetic regulation of myeloma
Multiple myeloma is in many ways a disease driven by inappropriate gene expression. It is characterised by the aberrant activation of gene regulatory elements known as enhancers, stimulating the upregulation of key oncogenes. Blocking this behaviour is therefore a promising strategy for myeloma treatment, and many therapeutic strategies directly or indirectly target gene regulatory pathways.
The lab studies the epigenetic regulation of gene expression, focused on the way these processes are dysregulated in multiple myeloma. We have a particular interest in understanding the role of oncogenic enhancer activity in driving myeloma-specific transcriptional profiles, and identifying the factors responsible for this behaviour. A major goal of the lab is to identify potential therapeutic targets that could be developed as novel therapies for multiple myeloma.
We use a variety of high-throughput genomics techniques to study the chromatin landscape, including ChIP-seq, ATAC-seq and RNA-seq. We have optimised TOPmentation, a small cell-number technique that allows us to characterise the chromatin profile of myeloma patient samples. In addition, we use the 3C technology Micro-Capture-C to map the physical association of enhancers and promoters. By combining these techniques with genetic and pharmacological manipulation of myeloma cell lines, we are able to explore mechanistically enhancer function and regulation.
Mechanisms of myeloma drug resistance
Relapse is very common in myeloma after initial treatment. Patients typically enter remission following treatment, but invariably relapse, often with resistance to one or more of these drugs. There is therefore a pressing need to understand the mechanisms that drive this resistance to find ways to counteract it. We are working to identify and understand epigenetic mechanisms that drive drug resistance via changes in gene expression, which therefore may be reversed to resensitise cells to therapy.
Our team
Nick Crump (he/him)
Nick Crump (he/him)
Kay Kendall Leukaemia Fund Intermediate Fellow
Jinglin Zhou (he/him)
Jinglin Zhou (he/him)
PhD student
Jason Taslim (he/him)
Jason Taslim (he/him)
Research assistant
Sophie Ball (she/her)
Sophie Ball (she/her)
PhD student
Funders
Research Publications
Results
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Journal articleRice S, Jackson T, Crump NT, et al., 2021,
A human fetal liver-derived infant MLL-AF4 acute lymphoblastic leukemia model reveals a distinct fetal gene expression program
, Nature Communications, Vol: 12, ISSN: 2041-1723Although 90% of children with acute lymphoblastic leukemia (ALL) are now cured, the prognosis for infant-ALL remains dismal. Infant-ALL is usually caused by a single genetic hit that arises in utero: an MLL/KMT2A gene rearrangement (MLL-r). This is sufficient to induce a uniquely aggressive and treatment-refractory leukemia compared to older children. The reasons for disparate outcomes in patients of different ages with identical driver mutations are unknown. Using the most common MLL-r in infant-ALL, MLL-AF4, as a disease model, we show that fetal-specific gene expression programs are maintained in MLL-AF4 infant-ALL but not in MLL-AF4 childhood-ALL. We use CRISPR-Cas9 gene editing of primary human fetal liver hematopoietic cells to produce a t(4;11)/MLL-AF4 translocation, which replicates the clinical features of infant-ALL and drives infant-ALL-specific and fetal-specific gene expression programs. These data support the hypothesis that fetal-specific gene expression programs cooperate with MLL-AF4 to initiate and maintain the distinct biology of infant-ALL.
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Journal articleHua P, Badat M, Hanssen LLP, et al., 2021,
Defining genome architecture at base-pair resolution
, Nature, Vol: 595, Pages: 125-129, ISSN: 0028-0836In higher eukaryotes, many genes are regulated by enhancers that are 104–106 base pairs (bp) away from the promoter. Enhancers contain transcription-factor-binding sites (which are typically around 7–22 bp), and physical contact between the promoters and enhancers is thought to be required to modulate gene expression. Although chromatin architecture has been mapped extensively at resolutions of 1 kilobase and above; it has not been possible to define physical contacts at the scale of the proteins that determine gene expression. Here we define these interactions in detail using a chromosome conformation capture method (Micro-Capture-C) that enables the physical contacts between different classes of regulatory elements to be determined at base-pair resolution. We find that highly punctate contacts occur between enhancers, promoters and CCCTC-binding factor (CTCF) sites and we show that transcription factors have an important role in the maintenance of the contacts between enhancers and promoters. Our data show that interactions between CTCF sites are increased when active promoters and enhancers are located within the intervening chromatin. This supports a model in which chromatin loop extrusion1 is dependent on cohesin loading at active promoters and enhancers, which explains the formation of tissue-specific chromatin domains without changes in CTCF binding.
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Journal articleHarman JR, Thorne R, Jamilly M, et al., 2021,
A KMT2A-AFFI gene regulatory network highlights the role of core transcription factors and reveals the regulatory logic of key downstream target genes
, Genome Research, Vol: 31, Pages: 1159-1173, ISSN: 1054-9803Regulatory interactions mediated by transcription factors (TFs) make up complex networks that control cellular behavior. Fully understanding these gene regulatory networks (GRNs) offers greater insight into the consequences of disease-causing perturbations than can be achieved by studying single TF binding events in isolation. Chromosomal translocations of the lysine methyltransferase 2A (KMT2A) gene produce KMT2A fusion proteins such as KMT2A-AFF1 (previously MLL-AF4), causing poor prognosis acute lymphoblastic leukemias (ALLs) that sometimes relapse as acute myeloid leukemias (AMLs). KMT2A-AFF1 drives leukemogenesis through direct binding and inducing the aberrant overexpression of key genes, such as the anti-apoptotic factor BCL2 and the proto-oncogene MYC. However, studying direct binding alone does not incorporate possible network-generated regulatory outputs, including the indirect induction of gene repression. To better understand the KMT2A-AFF1-driven regulatory landscape, we integrated ChIP-seq, patient RNA-seq, and CRISPR essentiality screens to generate a model GRN. This GRN identified several key transcription factors such as RUNX1 that regulate target genes downstream of KMT2A-AFF1 using feed-forward loop (FFL) and cascade motifs. A core set of nodes are present in both ALL and AML, and CRISPR screening revealed several factors that help mediate response to the drug venetoclax. Using our GRN, we then identified a KMT2A-AFF1:RUNX1 cascade that represses CASP9, as well as KMT2A-AFF1-driven FFLs that regulate BCL2 and MYC through combinatorial TF activity. This illustrates how our GRN can be used to better connect KMT2A-AFF1 behavior to downstream pathways that contribute to leukemogenesis, and potentially predict shifts in gene expression that mediate drug response.
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Journal articleCrump NT, Hadjinicolaou A, Xia M, et al., 2021,
Chromatin accessibility governs the differential response of cancer and T cells to arginine starvation
, Cell Reports, Vol: 35, ISSN: 2211-1247Depleting the microenvironment of important nutrients such as arginine is a key strategy for immune evasion by cancer cells. Many tumors overexpress arginase, but it is unclear how these cancers, but not T cells, tolerate arginine depletion. In this study, we show that tumor cells synthesize arginine from citrulline by upregulating argininosuccinate synthetase 1 (ASS1). Under arginine starvation, ASS1 transcription is induced by ATF4 and CEBPβ binding to an enhancer within ASS1. T cells cannot induce ASS1, despite the presence of active ATF4 and CEBPβ, as the gene is repressed. Arginine starvation drives global chromatin compaction and repressive histone methylation, which disrupts ATF4/CEBPβ binding and target gene transcription. We find that T cell activation is impaired in arginine-depleted conditions, with significant metabolic perturbation linked to incomplete chromatin remodeling and misregulation of key genes. Our results highlight a T cell behavior mediated by nutritional stress, exploited by cancer cells to enable pathological immune evasion.
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Journal articleCrump NT, Ballabio E, Godfrey L, et al., 2021,
BET inhibition disrupts transcription but retains enhancer-promoter contact
, Nature Communications, Vol: 12, ISSN: 2041-1723Enhancers are DNA sequences that enable complex temporal and tissue-specific regulation of genes in higher eukaryotes. Although it is not entirely clear how enhancer-promoter interactions can increase gene expression, this proximity has been observed in multiple systems at multiple loci and is thought to be essential for the maintenance of gene expression. Bromodomain and Extra-Terminal domain (BET) and Mediator proteins have been shown capable of forming phase condensates and are thought to be essential for super-enhancer function. Here, we show that targeting of cells with inhibitors of BET proteins or pharmacological degradation of BET protein Bromodomain-containing protein 4 (BRD4) has a strong impact on transcription but very little impact on enhancer-promoter interactions. Dissolving phase condensates reduces BRD4 and Mediator binding at enhancers and can also strongly affect gene transcription, without disrupting enhancer-promoter interactions. These results suggest that activation of transcription and maintenance of enhancer-promoter interactions are separable events. Our findings further indicate that enhancer-promoter interactions are not dependent on high levels of BRD4 and Mediator, and are likely maintained by a complex set of factors including additional activator complexes and, at some sites, CTCF and cohesin.
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