Biology subjects

Hall, M. W. J.

Publications and source records attributed to Hall, M. W. J..

8 recordsLinked to original sources

bioRxiv2024

Somatic mutant selection is altered by prior NOTCH1 mutation in aging esophageal epithelium

The ageing mid esophagus is progressively colonized by somatic mutations, including oncogenic TP53 and antioncogenic NOTCH1 mutants. Most esophageal squamous carcinomas are TP53 mutant, NOTCH1 wild type. By middle age, much of the esophagus is NOTCH1 mutant. We hypothesised that prior NOTCH1 mutation may alter subsequent mutant selection. Here we show that selection of mutant NOTCH2 was increased and mutant TP53 decreased within NOTCH1 mutant epithelium. Potential mechanisms include spatial competition between adjacent clones and/or epistasis altering the fitness NOTCH1 double mutants. We investigated these possibilities in transgenic mice. Spontaneous Notch2 mutant clones emerged in aged Notch1 null, but not wild type, esophagus, consistent with epistasis increasing Notch1/Notch2 double mutant fitness. However, there was no evidence of epistasis between Notch1 and Trp53, as Notch1 mutation alone increased fitness. In consequence, over time, Trp53 mutant Notch1 wild type clones were outcompeted by expanding Notch1 and Trp53/Notch1 mutants. NOTCH1 mutant takeover of the aging esophagus alters the trajectory of somatic evolution, decreasing selection of TP53 mutants and potentially reducing cancer risk.

genomics↗

bioRxiv2021

Notch1 mutation drives clonal expansion in normal esophageal epithelium but impairs tumor growth

NOTCH1 mutant clones occupy the majority of normal human esophagus by middle age, but are comparatively rare in esophageal cancers, suggesting NOTCH1 mutations may promote clonal expansion but impede carcinogenesis1-3. Here we test this hypothesis. Visualizing and sequencing NOTCH1 mutant clones in aging normal human esophagus reveals frequent biallelic mutations that block NOTCH1 signaling. In mouse esophagus, heterozygous Notch1 mutation confers a competitive advantage over wild type cells, an effect enhanced by loss of the second allele. Notch1 loss alters transcription but has minimal effects on epithelial structure and cell dynamics. In a carcinogenesis model, Notch1 mutations were less prevalent in tumors than normal epithelium. Deletion of Notch1 reduced tumor growth, an effect recapitulated by anti-NOTCH1 antibody treatment. We conclude that Notch1 mutations in normal epithelium are beneficial as wild type Notch1 promotes tumor expansion. NOTCH1 blockade may have therapeutic potential in preventing esophageal squamous cancer.

cancer biology↗

bioRxiv2020

Different responses to cell crowding determine the clonal fitness of p53 and Notch inhibiting mutations in squamous epithelia

The growth and competition of cells in epithelial tissues plays an important role in both tissue homeostasis and the robustness of normal tissues to pre-cancer mutation. Whilst wild-type cells compete neutrally for dominance in the un-mutated tissue, naturally occurring mutations in individual cells may lend them a fitness advantage that can allow tissue colonisation. In mouse oesophageal epithelia, the growth of p53 mutants and a dominant negative mutant of the Notch downstream target Maml1 (DN_Maml1) have been shown to have different colonisation properties despite strong quantitative similarities in the growth of individual clones. Here we show that in order to recapitulate these behaviours whilst maintaining tissue turnover models need to take account of the response of cells to increased areal density in the tissue colonised by mutant cells. We demonstrate that p53 mutant clone growth approximates a logistic curve, but that without including limitations on mutation induced expansion the overall proliferation rate of the tissue drops due to space restrictions. In contrast, the ability of DN_Maml1 mutations to displace the wild-type population reflects a feedback that effects both mutant and wild-type cells equally. We go on to show how these distinct feedbacks are consistent with the distribution of mutations observed in human datasets.

systems biology↗

bioRxiv2020

Investigating structure function relationships in the NOTCH family through large-scale somatic DNA sequencing studies

The recent development of highly sensitive DNA sequencing techniques has detected large numbers of missense mutations of genes, including NOTCH1 and 2, in ageing normal tissues. Driver mutations persist and propagate in the tissue through a selective advantage over both wild-type cells and alternative mutations. This process of selection can be considered as a large scale, in vivo screen for mutations that increase clone fitness. It follows that the specific missense mutations that are observed in individual genes may offer us insights into the structure-function relationships. Here we show that the positively selected missense mutations in NOTCH1 and NOTCH2 in human oesophageal epithelium cause inactivation predominantly through protein misfolding. Once these mutations are excluded, we further find statistically significant evidence for selection at the ligand binding interface and calcium binding sites. In this, we observe stronger evidence of selection at the ligand interface on EGF12 over EGF11, suggesting that in this tissue EGF12 may play a more important role in ligand interaction. Finally, we show how a mutation hotspot in the NOTCH1 transmembrane helix arises through the intersection of both a high mutation rate and residue conservation. Together these insights offer a route to understanding the mechanism of protein function through in vivo mutant selection.

biophysics↗

bioRxiv2020

KCNQ gene family members act as both tumor suppressors and oncogenes in gastrointestinal cancers

Voltage sensitive potassium channels play an important role in controlling membrane potential and ionic homeostasis in the gut and have been implicated in gastrointestinal (GI) cancers. Through large scale analysis of 1594 patients with GI cancers coupled with in vitro models we find KCNQ family genes are mutated in ~30% of patients, and play therapeutically targetable roles in GI cancer growth. KCNQ1 and KCNQ3 mediate the WNT pathway and MYC to increase proliferation, and its resultant effects on cadherins junctions. This also highlights novel roles for KCNQ3 in non-excitable tissues. We additionally discover that activity of KCNQ3 sensitises cancer cells to existing potassium channel inhibitors, and that inhibition of KCNQ activity reduces proliferation of GI cancer. These findings reveal a novel and exploitable role for potassium channels in the advancement of human cancer, and highlight that supplemental treatments for GI cancers may exist through KCNQ inhibitors. SIGNIFICANCEKCNQ channels modulate the WNT pathway and MYC signalling, and drive growth of gastrointestinal cancers. Available drugs modulate these pathways and offer therapeutic potential in gastrointestinal cancer.

cancer biology↗

bioRxiv2020

Methods for analysing lineage tracing datasets

A single population of stem cells maintains many epithelial tissues. Transgenic mouse cell tracking has frequently been used to study the growth dynamics of competing clones in these tissues. A mathematical model (the single progenitor model) has been argued to reproduce the observed stem cell dynamics accurately. This requires three parameters to describe the growth dynamics observed in transgenic mouse cell tracking- a division rate, a stratification rate, and the probability of dividing symmetrically. Deriving these parameters is time intensive and complex process. We compare the alternative strategies for analysing this source of experimental data, identifying an approximate Bayesian computation-based approach as the best in terms of efficiency and appropriate error estimation. We support our findings by explicitly modelling biological variation and consider the impact of different sampling regimes. All tested solutions are made available to allow new datasets to be analysed following our workflows. Based on our findings we make recommendations for future experimental design.

systems biology↗

bioRxiv2019

The Landscape of Mutations in Fumarate Hydratase

Fumarate Hydratase (FH) is an enzyme of the citric acid (TCA) cycle that is responsible for reversibly catalysing the conversion between fumarate and malate. FH loss and subsequent buildup of the oncometabolite fumarate causes hereditary leiomyomatosis and renal cell carcinoma. We explore the mutational landscape of FH in silico, predict the functional effects of many already detected mutations, and categorise detected but un-characterised mutations in human populations. Using mutational energy predicting tools such as Rosetta and FoldX we accurately predict mutations and mutational hotspots with high disruptive capability. Furthermore, through performing molecular dynamics simulations we show that hinge regions of the protein can be stabilized or destabilized by mutations, with new mechanistic implications of the consequences on the binding affinity of the enzyme for its substrates. Finally, we categorise all potential mutations in FH into functional groups, and predict which known mutations in the human population are loss-of-function, and therefore predispose patients to papillary renal carcinoma - we validate our findings through analysis of metabolomics data of characterized cell lines.

biophysics↗

bioRxiv2018

Relating evolutionary selection and mutant clonal dynamics in normal epithelia

Cancer develops from mutated cells in normal tissues. Whether somatic mutations alter normal cell dynamics is key to understanding cancer risk and guiding interventions to reduce it. An analysis of the first incomplete moment of size distributions of clones carrying cancer-associated mutations in normal human eyelid skin gives a good fit with neutral drift, arguing mutations do not affect cell fate. However, this suggestion conflicts with genetic evidence in the same dataset that argues for strong positive selection of a subset of mutations. This implies cells carrying these mutations have a competitive advantage over normal cells, leading to large clonal expansions within the tissue. In normal epithelium, clone growth is constrained by the limited size of the proliferating compartment and competition with surrounding cells. We show that if these factors are taken into account, the first incomplete moment of the clone size distribution is unable to exclude non-neutral behavior. Furthermore, experimental factors can make a non-neutral clone size distribution appear neutral. We validate these principles with a new experimental data set showing that when experiments are appropriately designed, the first incomplete moment can be a useful indicator of non-neutral competition. Finally, we discuss the complex relationship between mutant clone sizes and genetic selection.\n\nSignificance StatementAging normal epithelial tissues are extensively colonised by clones carrying cancer associated mutations. Insight into the emergence of mutant clones is key to guide cancer prevention. However, the statistical evidence as to whether mutant clones emerge by neutral competition or due to a competitive advantage conferred by mutation is conflicted. We reconcile this apparent contradiction by demonstrating that the previously presented metrics for measuring neutrality from clone sizes are dependent on the spatial constraints imposed by the tissue structure and experimental design. Furthermore, we show that clonal competition within a recently reported dataset of healthy human oesophageal tissue is non-neutral. Finally, we discuss how discrepancies between measures of clone size and genetic selection can provide insight into early carcinogenesis.

cancer biology↗