Biology subjects

Thomas, H.

Publications and source records attributed to Thomas, H..

26 records · Page 2Linked to original sources

bioRxiv2021

Elevated Neuropeptide Y1 Receptor Signaling Contributes to β-cell Dysfunction and Failure in Type 2 Diabetes

Loss of functional {beta}-cell mass is a key factor contributing to the poor glycaemic control in type 2 diabetes. However, therapies that directly target these underlying processes remains lacking. Here we demonstrate that gene expression of neuropeptide Y1 receptor and its ligand, neuropeptide Y, was significantly upregulated in human islets from subjects with type 2 diabetes. Importantly, the reduced insulin secretion in type 2 diabetes was associated with increased neuropeptide Y and Y1 receptor expression in human islets. Consistently, pharmacological inhibition of Y1 receptors by BIBO3304 significantly protected {beta}-cells from dysfunction and death under multiple diabetogenic conditions in islets. In a preclinical study, Y1 receptor antagonist BIBO3304 treatment improved {beta}-cell function and preserved functional {beta}-cell mass, thereby resulting in better glycaemic control in both high-fat-diet/multiple low-dose streptozotocin- and db/db type 2 diabetic mice. Collectively, our results uncovered a novel causal link of increased islet NPY-Y1 receptor signaling to {beta}-cell dysfunction and failure in human type 2 diabetes. These results further demonstrate that inhibition of Y1 receptor by BIBO3304 represents a novel and effective {beta}-cell protective therapy for improving functional {beta}-cell mass and glycaemic control in type 2 diabetes.

cell biology↗

bioRxiv2021

Germline loss-of-function variants in the base-excision repair gene MBD4 cause a Mendelian recessive syndrome of adenomatous colorectal polyposis and acute myeloid leukaemia

Inherited defects in base-excision repair (BER) predispose to adenomatous polyposis and colorectal cancer (CRC), yet our understanding of this important DNA repair pathway remains incomplete. By combining detailed clinical, histological and molecular profiling, we reveal biallelic germline loss-of-function (LOF) variants in the BER gene MBD4 to predispose to adenomatous polyposis and -uniquely amongst CRC predisposition syndromes- to myeloid neoplasms. Neoplasms from MBD4-deficient patients almost exclusively accumulate somatic CpG>TpG mutations, resembling mutational signature SBS1. MBD4-deficient adenomas harbour mutations in known CRC driver genes, although AMER1 mutations were more common and KRAS mutations less frequent. We did not find an increased risk for colorectal tumours in individuals with a monoallelic MBD4 LOF variant. We suggest that this condition should be termed MBD4-associated neoplasia syndrome (MANS) and that MBD4 is included in testing for the genetic diagnosis of polyposis and/or early-onset AML.

genetics↗

bioRxiv2021

SARS-CoV-2 comprehensive receptor profiling: mechanistic insight to drive new therapeutic strategies

Here we describe a hypothesis free approach to screen for interactions of SARS-CoV-2 spike (S) protein with human cell surface receptors. We used a library screening approach to detect binding interactions across one of the largest known panels of membrane-bound and soluble receptors, comprising 5845 targets, expressed recombinantly in human cells. We were able confirm and replicate SARS-CoV-2 binding to ACE2 and other putative coreceptors such as CD209 and CLEC4M. More significantly, we identified interactions with a number of novel SARS-CoV-2 S binding proteins. Three of these novel receptors, NID1, CNTN1 and APOA4 were specific to SARS-CoV-2, and not SARS-COV, with APOA4 binding the S-protein with equal affinity as ACE2. With this knowledge we may further understand the disease pathogenesis of COVID-19 patients and how infection by SARS-CoV-2 may lead to differences in pathology in specific organs or indeed the virulence observed in different ethnicities. Importantly we illustrate a methodology which can be used for rapid, unbiassed identification of cell surface receptors, to support drug screening and drug repurposing approaches for this and future pandemics.

cell biology↗

bioRxiv2021

Gene regulatory networks for compatible versus incompatible grafts identify a role for SlWOX4 during junction formation

Graft incompatibility is a poorly understood phenomenon that presents a serious agricultural challenge. Unlike immediate incompatibility that results in rapid death, delayed incompatibility can take months or even years to manifest, creating a significant economic burden for perennial crop production. To gain insight into the genetic mechanisms underlying this phenomenon, we developed a model system with Solanum lycopersicum tomato and Capsicum annuum pepper heterografting, which expresses signs of anatomical junction failure within the first week of grafting. By generating a detailed timeline for junction formation we were able to pinpoint the cellular basis for this delayed incompatibility. Furthermore, we infer gene regulatory networks for compatible self-grafts versus incompatible heterografts based on these key anatomical events, which predict core regulators for grafting. Finally, we delve into the role of vascular development in graft formation and validate SlWOX4 as a regulator for grafting in tomato. Notably, SlWOX4 is the first gene to be functionally implicated in vegetable crop grafting.

plant biology↗

bioRxiv2020

Platelet Derived Growth Factor Receptor β (PDGFRβ) is a Host Receptor for the human malaria parasite adhesin TRAP

Following their inoculation by the bite of an infected Anopheles mosquito, the malaria parasite sporozoite forms travel from the bite site in the skin into the bloodstream, which transports them to the liver. The thrombospondin-related anonymous protein (TRAP) is a type 1 transmembrane protein that is released from secretory organelles and relocalized on the sporozoite plasma membrane. TRAP is required for sporozoite motility and host infection, and its extracellular portion contains adhesive domains that are predicted to engage host receptors. Here, we identified the human platelet-derived growth factor receptor {beta} (hPDGFR{beta}) as one such protein receptor. Deletion mutants showed that the von Willebrand factor type A and thrombospondin repeat domains of TRAP are both required for optimal binding to hPDGFR{beta}-expressing cells. We also demonstrate that this interaction is conserved in the human-infective parasite Plasmodium vivax, but not the rodent-infective parasite Plasmodium yoelii. We observed expression of hPDGFR{beta} mainly in cells associated with the vasculature suggesting that TRAP:hPDGFR{beta} interaction may play a role in the recognition of blood vessels by invading sporozoites.

microbiology↗

bioRxiv2020

Detailed temporal dissection of an enhancer cluster reveals two distinct roles for individual elements

Many genes are regulated by multiple enhancers that often simultaneously activate their target gene. Yet, how individual enhancers collaborate to activate transcription is not well understood. Here, we dissect the functions and interdependencies of five enhancer elements that form a previously identified enhancer cluster and activate the Fgf5 locus during exit from naive murine pluripotency. Four elements are located downstream of the Fgf5 gene and form a super-enhancer. Each of these elements contributes to Fgf5 induction at a distinct time point of differentiation. The fifth element is located in the first intron of the Fgf5 gene and contributes to Fgf5 expression at every time point by amplifying overall Fgf5 expression levels. This amplifier element strongly accumulates paused RNA Polymerase II but does not give rise to a mature Fgf5 mRNA. By transplanting the amplifier to a different genomic position, we demonstrate that it enriches for high levels of paused RNA Polymerase II autonomously. Based on our data, we propose a model for a mechanism by which RNA Polymerase II accumulation at a novel type of enhancer element, the amplifier, contributes to enhancer collaboration.

molecular biology↗

bioRxiv2019

Replacing murine insulin 1 with human insulin protects NOD mice from diabetes

Type 1, or autoimmune, diabetes is caused by the T-cell mediated destruction of the insulin-producing pancreatic beta cells. Non-obese diabetic (NOD) mice spontaneously develop autoimmune diabetes akin to human type 1 diabetes. For this reason, the NOD mouse has been the preeminent murine model for human type 1 diabetes research for several decades. However, humanized mouse models are highly sought after because they offer both the experimental tractability of a mouse model and the clinical relevance of human-based research. Autoimmune T-cell responses against insulin, and its precursor proinsulin, play central roles in the autoimmune responses against pancreatic beta cells in both humans and NOD mice. As a first step towards developing a murine model of the human autoimmune response against pancreatic beta cells we set out to replace the murine insulin 1 gene (Ins1) with the human insulin gene (INS) using CRISPR/Cas9. Here we describe a NOD mouse strain that expresses human insulin in place of murine insulin 1, referred to as HuPI. HuPI mice express human insulin, and C-peptide, in their serum and pancreata and have normal glucose tolerance. Compared with wild type NOD mice, the incidence of diabetes is much lower in HuPI mice. Only 15-20% of HuPI mice developed diabetes after 300 days, compared to more than 60% of unmodified NOD mice. Immune-cell infiltration into the pancreatic islets of HuPI mice was not detectable at 100 days but was clearly evident by 300 days. This work highlights the feasibility of using CRISPR/Cas9 to create mouse models of human diseases that express proteins pivotal to the human disease. Furthermore, it reveals that even subtle changes in proinsulin protect NOD mice from diabetes.

immunology↗

bioRxiv2019

A nucleotide resolution map of Top2-linked DNA breaks in the yeast and human genome

DNA topoisomerases are required to resolve DNA topological stress. Despite this essential role, abortive topoisomerase activity generates aberrant protein-linked DNA breaks, jeopardising genome stability. Here, to understand the genomic distribution and mechanisms underpinning topoisomerase-induced DNA breaks, we map Top2 DNA cleavage with strand-specific nucleotide resolution across the S. cerevisiae and human genomes--and use the meiotic Spo11 protein to validate the broad applicability of this method to explore the role of diverse topoisomerase family members. Our data characterises Mre11-dependent repair in yeast, and defines two strikingly different fractions of Top2 activity in humans: tightly localised CTCF-proximal, and broadly distributed transcription-proximal, the latter correlated with gene length and expression. Moreover, single nucleotide accuracy enables us to reveal the influence primary DNA sequence has upon Top2 cleavage--distinguishing canonical DNA double-strand breaks (DSBs) from a major population of DNA single-strand breaks (SSBs) induced by etoposide (VP16) in vivo.

molecular biology↗