Researchers at the Crick are tackling the big questions about human health and disease, and new findings are published every week. Our faculty have picked some of the most significant papers published by Crick scientists, all of which are freely available thanks to our open science policy.
Versatile humanized niche model enables study of normal and malignant human hematopoiesis
Immunodeficient mouse models have been instrumental in improving our understanding of human healthy haemopoietic stem cells and their hierarchical organisation as well as of the functional and phenotypic heterogeneity of leukaemic stem cells in acute myeloid leukaemia. However, xenotransplantation models failed at reconstituting the human bone marrow niche which remains of mouse origin. Using a bioengineered scaffold, we developed a new versatile humanised bone marrow niche which supports the engraftment of both normal and leukaemia stem cells in vivo. This 3D scaffold represents a suitable model to study and dissect the human bone marrow composition and test the effect of specific stroma cell types and niche factor functions during both normal human haemopoiesis and leukaemia.
Decoding of position in the developing neural tube from antiparallel morphogen gradients
Like many developing tissues, the vertebrate neural tube is patterned by antiparallel morphogen gradients. Using quantitative gene expression and signalling measurements we derived and validated a characteristic decoding map that relates morphogen input to the positional identity of neural progenitors. This revealed a strategy that minimises patterning errors in response to the joint input of noisy opposing gradients. The study illustrates how we integrate quantitative data, developmental and microfluidic experiments with phenological and mechanistic models.
A supramolecular assembly mediates lentiviral DNA integration
Lentiviral IN proteins are notoriously poorly behaved in vitro, and the HIV 1 intasome has eluded structural biologists for over two decades. Prior research resulted in a collection of partial crystal and NMR structures that did not explain how lentiviral integrase synapses viral DNA ends. This paper described the first structure of the lentiviral intasome, solving the long-standing mystery and reconciling years of HIV-1 integrase structural biology and biochemistry.
Bidirectional eukaryotic DNA replication is established by quasi-symmetrical helicase loading
This paper shows that loading of the MCM double hexamer is a quasi-symmetrical reaction: two ORC molecules bound at two opposing sites of different affinity each recruit and load a single hexamer. The distance between the ORC binding sites is not critical. Subsequent work has provided further evidence for this from cryo-EM.
Phosphopeptide binding by Sld3 links Dbf4-dependent kinase to MCM replicative helicase activation
Here we showed that Sld3, which we previously identified as being one of two essential cyclin dependent kinase (CDK) substrates in replication, is a phosphopeptide binding protein which binds specifically to Mcm4 and Mcm6 when they have been phosphorylated by Dbf4 dependent kinase (DDK). Sld3 then directly recruits Cdc45 to MCM and, via CDK phosphorylation, recruits the remaining firing factors. We had previously shown that Sld3 is also one of two targets of the DNA damage checkpoint kinase involved in inhibiting origin firing in response to DNA damage. Thus, Sld3 plays key roles with all three kinases that regulate replication (CDK, DDK, Rad53).
Chromatin controls DNA replication origin selection, lagging-strand synthesis, and replication fork rates
In this and the accompanying paper (Yeeles et al. 2017 Mol Cel 65, 105-116) we describe the reconstitution of full chromatin replication. We first identified all of the factors required for complete and rapid replication of naked DNA. Then we identified and characterised factors required to replicate chromatinised templates. We showed FACT is essential for chromatin replication, whilst nucleosome remodellers and histone acetylases help chromatin replication. In addition, chromatin enforces origin specificity and Okazaki fragment processing. Finally, we found that histones are efficiently transferred to nascent DNA.
Oncogenic RAS signaling promotes tumor immunoresistance by stabilizing PD-L1 mRNA
This work establishes for the first time a link between oncogenic RAS signalling and increased immuno-suppressive expression of the immune checkpoint protein PD-L1. RAS signalling results in phosphorylation and inactivation of TTP, a factor involved in degrading PD-L1 mRNA transcripts. As TTP inactivation causes accumulation of PD-L1 mRNA, interfering with the RAS pathway increases TTP binding to AU-rich elements of the transcripts, decreases PD-L1 protein production, and leads to enhanced antitumor immunity.
aPKC cycles between functionally distinct PAR protein assemblies to drive cell polarity
Through the use of aPKC inhibitors and genetic mutations, we demonstrate that aPKC cycles between distinct PAR-3 and CDC-42 dependent states, which define, respectively, the ability of the aPAR network to respond to spatial cues and to displace pPAR proteins from the membrane. We further show that cue sensing depends crucially on the oligomeric nature of the PAR-3 state, that the integrity of this cycle is required for coupling of cue-sensing and effector functions of the aPAR network, and that this cycle is enforced by activity of aPKC.
Return to quiescence of mouse neural stem cells by degradation of a proactivation protein
This paper provided the first evidence that stem cells in the adult mouse hippocampus are heterogeneous in their behaviour, with most stem cells differentiating and leaving the niche after they have become active but a small fraction returning to a shallow state of quiescence. These “resting cells” have an essential role in the long-term maintenance of an active stem cell pool.
Epithelia use butyrophilin-like molecules to shape organ-specific γδ T cell compartments
This paper established that intestinal epithelial cells use BTNL/Btnl molecules to select for and regulate tissue-specific gamma delta T cell compartments. It established a biological mechanism by which epithelial cells communicate with local T cells at steady-state (“normality sensing”). Following on from our prototypic discovery of such a mechanism in mouse skin, the work established conservation of the process across tissues as well as across species. The system is unperturbed by microbial colonisation.
Genome editing reveals a role for OCT4 in human embryogenesis
The first demonstration of the utility of CRISPR–Cas9-mediated genome editing for investigating gene function in the context of human embryonic development. We revealed a distinct role for the developmental regulator OCT4 in human versus mouse development.
CDK substrate phosphorylation and ordering the cell cycle
A phosphoproteomics analysis of CDK substrates has shown that the correct cell cycle temporal order of CDK substrate phosphorylation can be established by a single CDK. It is shown that there is a 50-fold increase of in vivo CDK activity during the cell cycle. Temporal order is achieved by a combination of this rise with differential sensitivity of substrates to CDK activity. Phosphosite turnover is very rapid which helps ensure sharp cell cycle transitions.
Lineage-dependent spatial and functional organization of the mammalian enteric nervous system
In this paper we use genetic lineage tracing and clonal analysis to characterise mammalian enteric nervous system progenitors, define differentiation trajectories for enteric neurons and glia during development and propose a new model for the 3-D organisation of the enteric nervous system.
Reactive oxygen species localization programs inflammation to clear microbes of different size
How inflammatory programmes are tuned to recruit sufficient numbers of neutrophils to clear microbes of different size remained unknown. Furthermore, neutrophils were not thought to serve as major regulators of inflammation in vivo. We showed that reactive oxygen species localisation allows neutrophils to regulate their own recruitment by setting the appropriate level of cytokine production.
A neuroprotective astrocyte state is induced by neuronal signal EphB1 but fails in ALS models
We addressed the hypothesis that impairment of neuroprotective astrocytic mechanisms are disrupted in ALS using in vivo models, and patient-specific iPSCs. We found that EphB1, a neuronal signal, can induce a neuroprotective astrocyte phenotype through the EphrinB1 receptor / JAK-STAT pathway and that this response fails in ALS astrocytes.
A mechanically active heterotypic E-cadherin/N-cadherin adhesion enables fibroblasts to drive cancer cell invasion
Our previous work showed how stromal fibroblasts lead the collective invasion of cancer cells, and documented how remodelling of the extracellular matrix was important for this behaviour. Following our observation of direct cell-cell contacts between cancer cells and fibroblasts, we hypothesised that the two cells might be mechanically coupled; therefore, we began collaborating with Xavi Trepat (IBEC Barcelona), who is a world leader in the mechanics of multi-cellular systems. By biophysical measurements and a range of conventional cell and molecular biology manipulations, we demonstrated that fibroblasts actively ‘pull’ cancer cells into the surrounding extracellular matrix.
The linker histone H1.0 generates epigenetic and functional intratumor heterogeneity
This study showed that epigenetic mechanisms play an important role in generating functional heterogeneity within tumours, and can override genetic alterations that initiate the disease by inhibiting cell proliferative potential during tumour growth. The finding that heterogeneous patterns of H1.0 are broadly observed in cancer and that H1.0 is an independent predictor of patient survival in multiple types of solid tumours makes a strong case for a general role of epigenetic regulators in cancer. Mechanistic characterisation of how H1.0 controls malignant self-renewing states also provided insights into general mechanisms through which the linker histone regulates gene expression.
Feedback control of AHR signalling regulates intestinal immunity
This paper established the AHR induced feedback system of cytochrome P4501 metabolising enzymes as critical regulators of AHR signalling. Excessive ligand degradation via Cytochrome P4501 phenocopies AHR deficiency and has detrimental consequences for intestinal health which can be counterbalanced by increasing the intake of AHR ligands in the diet. The intestinal epithelium acts as gatekeeper for the supply of ligands throughout the body emphasising the importance of the gut barrier for whole body physiology.
UV irradiation induces a non-coding RNA that functionally opposes the protein encoded by the same gene
A detailed, genome-wide study of the transcriptional response to DNA damage, including the identification of genes that start expressing short, alternative splice isoforms after genomic insult. One of these genes, ASCC3, normally expresses a protein-coding mRNA, but after UV-irradiation shifts expression to a short non-coding RNA isoform, which is important for survival after DNA damage. The protein-coding ASCC3 isoform counteracts the function of the non-coding isoform, indicating crosstalk between them.
Phylogenetic ctDNA analysis depicts early-stage lung cancer evolution
This TRACERx work shows that bespoke patient-specific panels to analyse ctDNA can be used to monitor MRD recurrence and tumour branched evolution in the adjuvant setting in the absence of macroscopic disease, and that tumour Ki67 index, necrosis, squamous histology and FDG-PET avidity are closely associated with ctDNA release. We further demonstrate the limitations of ctDNA approaches for early detection as a function of tumour volume and cancer cell number, and show that the subclone identified in ctDNA prior to disease recurrence is identical to the tumour subclone identified at metastatic sites, permitting adjuvant MRD studies to prevent recurrence.