Biology subjects

Evans, M. K.

Publications and source records attributed to Evans, M. K..

7 recordsLinked to original sources

bioRxiv2026

Expansion Microscopy reveals changes in cellular and extracellular structures between healthy and perturbed tendons

Tendons transmit mechanical forces between muscles and bones through their highly aligned, collagen-rich extracellular matrix. When damaged, resident cells help restore this matrix. However, in tendinopathies, this repair response fails, leading to loss of proper tendon function. How altered mechanical states reshape tendon cell and matrix architecture remains poorly understood because existing methods do not readily capture tendon structure across relevant length scales. Here, we combine Fluorescent Labeling of Abundant Reactive Entities (FLARE) with Expansion Microscopy (ExM) to visualize cellular and extracellular structures in native tendon tissue. FLARE-ExM resolves the dense fibrillar matrix across multiple tendon types, including elastic fibers and glycan-rich cellular protrusions. In a tendon resection model, acute loss-of-tension was associated with increased fibril width and expansion of carbohydrate- and protein-rich regions. In ruptured human Achilles tendon, FLARE-ExM revealed extracellular disorganization and disrupted cellular architecture. These results establish FLARE-ExM as a useful approach for studying how mechanical perturbation remodels tendon architecture across physiological and disease contexts.

physiology↗

bioRxiv2024

CTPS1 inhibition synergizes with replication stress signaling inhibition in MYC-amplified Group 3 medulloblastoma

MYC-driven medulloblastomas (MBs) represent the most aggressive and deadly subgroup of MB, the most common malignant pediatric brain tumor. Direct targeting of MYC itself remains an unmet clinical need, therefore focusing on vulnerabilities driven by MYC may be a viable option for novel therapeutic interventions. Using whole-genome CRISPR screening, we identified the de novo pyrimidine synthesis enzyme CTP synthase (CTPS1) as a strong dependency in MYC-driven MB. CTPS1 is the final and rate-limiting step in the de novo pyrimidine synthesis pathway. Targeted inhibition of CTPS1 leads to decreased tumor cell proliferation and markedly reduces MYC expression in G3 MB models. Mechanistically, we demonstrate that single agent CTPS1 inhibition activates the replication stress signaling pathway mediated by ATM-CHK2 and ATR-CHK1. Blockade of CHK1 kinase activity increases sensitivity to CTPS1 inhibition and significantly impedes heterotopic MB tumor growth. CTPS1 enzymatic activity requires the amino acid glutamine, therefore we inhibited CTPS1 using the glutamine antagonists, JHU083 and JHU395. These compounds are prodrugs of 6-diazo-5-oxo-L-norleucine (DON) which were developed to exhibit better tumor targeting and enhanced blood-brain barrier penetrability. Combining JHU083 and CHK1 inhibition demonstrates potent synergy against patient-derived MB xenografts in vivo. Our findings strongly suggest that combining de novo pyrimidine synthesis and ATR-CHK1 inhibitors is a promising treatment for MYC-driven MBs. Key PointsO_LICTPS1 is a unique vulnerability in MYC-driven medulloblastoma C_LIO_LICTPS1 inhibition activates the ATR-CHK1 replication stress response pathway for cell survival C_LIO_LIBlockade of CTPS1 enzymatic activity synergizes with CHK1 inhibition in vitro and in vivo C_LI Importance of the StudyMYC hyperactivation in tumors drives multiple anabolic processes which contribute to tumor proliferation and aggressiveness in patients. We show that targeting de novo pyrimidine synthesis (via CTPS1) limits tumor growth and targets MYC itself through a feedback mechanism. CTPS1 inhibition potently combines with CHK1 blockade and enhances disease control in both heterotopic and orthotopic models of medulloblastoma (MB). Our results support the clinical evaluation of combined CTPS1 and CHK1 inhibition in patients with MYC-driven MB.

cancer biology↗

bioRxiv2022

Poverty shapes the transcriptome of immune cells

Social factors influence health outcomes and life expectancy. Individuals living in poverty often have adverse health outcomes related to chronic inflammation that affect the cardiovascular, renal, and pulmonary systems. Negative psychosocial experiences are associated with transcriptional changes in genes associated with complex traits. However, the underlying molecular mechanisms by which poverty increases the risk of disease and health disparities are still not fully understood. To bridge the gap in our understanding of the link between living in poverty and adverse health outcomes, we performed RNA sequencing of blood immune cells from 204 participants of the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study in Baltimore, Maryland. We identified 138 genes differentially expressed in association with poverty. Genes differentially expressed were enriched in wound healing and coagulation processes. Of the genes differentially expressed in individuals living in poverty, EEF1DP7 and VIL1 are also associated with hypertension in transcriptome-wide association studies. Our results suggest that living in poverty influences inflammation and the risk for cardiovascular disease through gene expression changes in immune cells.

genomics↗

bioRxiv2022

Targeting the Hedgehog Signaling Pathway to Improve Tendon-to-Bone Integration

ObjectiveWhile the role of Hedgehog (Hh) signaling in promoting zonal fibrocartilage production during development is well-established, whether this pathway can be leveraged to improve tendon-to-bone repair in adults is unknown. Our objective was to genetically and pharmacologically stimulate the Hh pathway in cells that give rise to zonal fibrocartilaginous attachments to promote tendon-to-bone integration. DesignHh signaling was stimulated genetically, via constitutive Smo (SmoM2 construct) activation of activated bone marrow stromal cells, or pharmacologically, via systemic agonist delivery, to mice following anterior cruciate ligament reconstruction (ACLR). To assess tunnel integration, we measured mineralized fibrocartilage (MFC) formation in these mice 28 days post-surgery and performed tunnel pullout testing. ResultsHh pathway-related genes increased in cells forming the zonal attachments in WT mice. Both genetic and pharmacologic stimulation of the Hh pathway increased MFC formation and integration strength 28 days post-surgery. We next conducted studies to define the role of Hh in specific stages of the tunnel integration process. We found Hh agonist treatment increased proliferation of the progenitor pool in the first week post-surgery. Additionally, genetic stimulation led to continued MFC production in later stages of the integration process. These results indicate that Hh signaling plays an important biphasic role in cell proliferation and differentiation towards fibrochondrocytes following ACLR. ConclusionThis study reveals a biphasic role for Hh signaling during the tendon-to-bone integration process after ACLR. In addition, the Hh pathway is a promising therapeutic target to improve tendon-to-bone repair outcomes.

bioengineering↗

bioRxiv2022

Mechano-epigenetic regulation of extracellular matrix homeostasis via Yap and Taz

Cells integrate mechanical cues to direct fate specification to maintain tissue function and homeostasis. While disruption of these cues is known to lead to aberrant cell behavior and chronic diseases, such as tendinopathies, the underlying mechanisms by which mechanical signals maintain cell function is not well understood. Here, we show using a novel model of tendon de-tensioning that loss of tensile cues in vivo acutely changes nuclear morphology, positioning, and expression of catabolic gene programs. Using paired ATAC/RNAseq, we further identify that a loss of cellular tension rapidly reduces chromatin accessibility in the vicinity of Yap/Taz genomic targets while also increasing expression of genes involved in matrix catabolism. Overexpression of Yap results in a reduction of chromatin accessibility at matrix catabolic gene loci, while also reducing transcriptional levels. Concordantly, depletion of Yap/Taz elevates matrix catabolic expression. Finally, we demonstrate that overexpression of Yap not only prevents the induction of a broad catabolic program following a loss of cellular tension, but also preserves the underlying chromatin state from force-induced alterations. Taken together, these results provide novel mechanistic details by which mechanical signals regulate tendon cell function to preserve matrix homeostasis through a Yap/Taz axis. Significance StatementCells integrate mechanical signals to regulate biological outputs within tissues. These processes are required for tissue function and homeostasis. Here, we show how mechanical cues (e.g. tension) directs tendon cell function and fate at a transcriptional and epigenetic level. Furthermore, we show that disruption of these mechanical cues leads to a disease-like cell state, indicating these mechanosensitive pathways could be important for diseases driven by perturbed mechanical signaling, such as tendinopathy. Finally, we demonstrate that genetic perturbation of a single protein can preserve cell and chromatin state following a loss of tension, supporting novel avenues for the development of innovative mechano-therapeutics.

cell biology↗

bioRxiv2021

Ultra-cheap and scalable epigenetic age predictions with TIME-Seq

Epigenetic "clocks" based on DNA methylation (DNAme) have emerged as the most robust and widely employed aging biomarkers, but conventional methods for applying them are expensive and laborious. Here, we develop Tagmentation-based Indexing for Methylation Sequencing (TIME-Seq), a highly multiplexed and scalable method for low-cost epigenetic clocks. Using TIME-Seq, we applied multi-tissue and tissue-specific epigenetic clocks to over 1,600 mouse DNA samples. We also discovered a novel approach for age prediction from shallow sequencing (e.g., 10,000 reads) by adapting scAge for bulk measurements. In benchmarking experiments, TIME-Seq performed favorably against prevailing methods and could quantify the effects of interventions thought to accelerate, slow, and reverse aging in mice. Finally, we built and validated a highly accurate human blood clock from 1,056 demographically representative individuals. Our methods increase the scalability and reduce the cost of epigenetic age predictions by more than 100-fold, enabling accurate aging biomarkers to be applied in more large-scale animal and human studies.

genomics↗

bioRxiv2019

MicroRNA 1253 regulation of WAVE2 and its relevance to health disparities in hypertension

The prevalence of hypertension among African Americans (AAs) in the US is among the highest of any demographic and affects over two-thirds of AA women. Previous data from our laboratory suggests substantial differential gene expression (DGE) of mRNAs and microRNAs (miRNAs) exists within peripheral blood mononuclear cells (PBMCs) isolated from AA and white women with or without hypertension. We hypothesized that DGE by race may contribute to racial differences in hypertension. We found that the Wiskott-Aldrich syndrome protein Verprolin homologous-2 (WAVE2) is differentially-expressed in AA women with hypertension, along with several other members of the actin cytoskeleton signaling pathway that plays a role in cell shape and branching of actin filaments. We performed an in silico miRNA target prediction analysis that suggested miRNA miR-1253 regulates WAVE2. Transfection of miR-1253 mimics into human umbilical vein endothelial cells (HUVECs) and human aortic endothelial cells (HAECs) significantly repressed WAVE2 mRNA and protein levels (P<0.05), and a luciferase reporter assay confirmed that miR-1253 regulates the WAVE2 3 UTR (P<0.01). miR-1253 over-expression in HUVECs significantly increased HUVEC lamellipodia formation (P<0.01), suggesting the miR-1253/WAVE2 interaction may play a role in endothelial cell shape and actin cytoskeleton function. Together, we have identified novel roles for miR-1253 and WAVE2 in a hypertension-related disparities context. This may ultimately lead to the discovery of additional actin-related genes which are important in the vascular-related complications of hypertension and influence the disproportionate susceptibility to hypertension among AAs in general and AA women in particular.

cell biology↗