Biology subjects

Clark, K. A.

Publications and source records attributed to Clark, K. A..

7 recordsLinked to original sources

bioRxiv2025

Controlled Release of Poly(U) via Acetalated Dextran Microparticles for Enhanced Vaccine Adjuvant Delivery

Diverse drug delivery systems are needed to address challenges in delivering novel vaccine components and enhancing their efficacy. Poly(U) is a single-stranded RNA composed of uracil repeats that acts as a toll-like receptor (TLR) 7/8 agonist, stimulating the innate immune system. However, poly(U) is susceptible to ribonuclease degradation without a delivery carrier, and its negative charge hinders cellular uptake. Encapsulation in acetalated dextran (Ace-DEX), a pH-sensitive, biodegradable polymer, addresses these challenges. This study encapsulated poly(U) into Ace-DEX Microparticles (MPs) with either spherical (smooth MPs) or collapsed-surface (wrinkled MPs) via spray-drying. It was hypothesized that the different morphologies of MPs would influence the vaccine efficacy after in vitro and in vivo models. Smooth poly(U) MPs had a higher percent viability and cytokine response in dendritic cells (DCs) than wrinkled poly(U) MPs. Moreover, mice vaccinated with smooth poly(U) MPs + ovalbumin (OVA) showed enhanced IL-2 production and IFN-{gamma} in response to OVA peptide and MHC-I immunodominant peptide restimulation, respectively, compared to wrinkled poly(U) MPs. However, mice vaccinated with wrinkled poly(U) MPs + OVA significantly increased B-cell and germinal center B-cell frequencies compared to mice vaccinated with phosphate buffered saline (PBS) whereas mice vaccinated with smooth poly(U) MPs + OVA did not. Overall, these findings suggest that smooth poly(U) MPs modulated dendritic cells and T-cells, and wrinkled poly(U) MPs modulated B-cells. Understanding how morphology influences these cell types will aid in optimizing future vaccine systems for more specific cellular targeting.

bioengineering↗

bioRxiv2022

Inter-scanner brain MRI volumetric biases persist even in a harmonized multi-subject study of multiple sclerosis

Background/PurposeMulticenter study designs involving a variety of MRI scanners have become increasingly common. However, these present the issue of biases in image-based measures due to scanner or site differences. To assess these biases, we imaged 11 volunteers with multiple sclerosis (MS) with scan and rescan data at 4 sites. Materials and MethodsImages were acquired on Siemens or Philips scanners at 3-tesla. Automated white matter lesion detection and whole brain, gray and white matter, and thalamic volumetry were performed, as well as expert manual delineations of T1 and T2 (FLAIR) lesions. Random effect and permutation-based nonparametric modeling was performed to assess differences in estimated volumes within and across sites. ResultsRandom effect modeling demonstrated model assumption violations for most comparisons of interest. Non-parametric modeling indicated that site explained > 50% of the variation for most estimated volumes. This expanded to > 75% when data from both Siemens and Philips scanners were included. Permutation tests revealed significant differences between average inter- and intra-scanner differences in most estimated brain volumes (P < .05). The automatic activation of spine coil elements during some acquisitions resulted in a shading artifact in these images. Permutation tests revealed significant differences between thalamic volume measurements from acquisitions with and without this artifact. ConclusionDifferences in brain volumetry persisted across MR scanners despite protocol harmonization. These differences were not well explained by variance component modeling; however, statistical innovations for mitigating inter-scanner differences show promise in reducing biases in multi-center studies of MS.

neuroscience↗

bioRxiv2021

Evolution of the open-access CIViC knowledgebase is driven by the needsof the cancer variant interpretation community

CIViC (Clinical Interpretation of Variants in Cancer; civicdb.org) is a crowd-sourced, public domain knowledgebase composed of literature-derived evidence characterizing the clinical utility of cancer variants. As clinical sequencing becomes more prevalent in cancer management, the need for cancer variant interpretation has grown beyond the capability of any single institution. With nearly 300 contributors, CIViC contains peer-reviewed, published literature curated and expert-moderated into structured data units (Evidence Items) that can be accessed globally and in real time, reducing barriers to clinical variant knowledge sharing. We have extended CIViCs functionality to support emergent variant interpretation guidelines, increase interoperability with other variant resources, and promote widespread dissemination of structured curated data. To support the full breadth of variant interpretation from basic to translational, including integration of somatic and germline variant knowledge and inference of drug response, we have enabled curation of three new evidence types (predisposing, oncogenic and functional). The growing CIViC knowledgebase distributes clinically-relevant cancer variant data currently representing >2500 variants in >400 genes from >2800 publications.

genomics↗

bioRxiv2019

The CIViC knowledge model and standard operating procedures for curation and clinical interpretation of variants in cancer

Manually curated variant knowledgebases and their associated knowledge models are serving an increasingly important role in distributing and interpreting variants in cancer. These knowledgebases vary in their level of public accessibility, and the complexity of the models used to capture clinical knowledge. CIViC (Clinical Interpretations of Variants in Cancer - www.civicdb.org) is a fully open, free-to-use cancer variant interpretation knowledgebase that incorporates highly detailed curation of evidence obtained from peer-reviewed publications. Currently, the CIViC knowledge model consists of four main components: Genes, Variants, Evidence Items, and Assertions. Each component has an associated knowledge model and methods for curation. Gene and Variant data contextualize the genomic region(s) involved in the clinical statement. Evidence Items provide structured associations between variants and their clinically predictive/therapeutic, prognostic, diagnostic, predisposing, and functional implications. Finally, CIViC Assertions summarize collections of CIViC Evidence Items for a specific Disease, Variant, and Clinical Significance with incorporation of clinical and technical guidelines. Here we present the CIViC knowledge model, curation standard operating procedures, and detailed examples to support community-driven curation of cancer variants.

bioinformatics↗

bioRxiv2019

ETV4 is necessary for estrogen signaling and growth in endometrial cancer cells

Estrogen signaling through estrogen receptor alpha (ER) plays a major role in endometrial cancer risk and progression; however, the molecular mechanisms underlying ERs regulatory role in endometrial cancer are poorly understood. In breast cancer cells, ER genomic binding is enabled by FOXA1 and GATA3, but the transcription factors that control ER genomic binding in endometrial cancer cells remain unknown. We previously identified ETV4 as a candidate factor controlling ER genomic binding in endometrial cancer cells and here we explore the functional importance of ETV4. Homozygous deletion of ETV4, using CRISPR/Cas9, led to greatly reduced ER binding at the majority of loci normally bound by ER. Consistent with the dramatic loss of ER binding, the gene expression response to estradiol was dampened for most genes. ETV4 contributes to estrogen signaling in two distinct ways; ETV4 loss impacts chromatin accessibility at some ER bound loci and impairs ER nuclear translocation. The diminished estrogen signaling upon ETV4 deletion led to decreased growth, particularly in 3D culture where hollow organoids were formed and in vivo in the context of estrogen dependent growth. Our results show that ETV4 plays an important role in estrogen signaling in endometrial cancer cells.

molecular biology↗

bioRxiv2018

Electrostatic repulsion causes anticooperative DNA binding between tumor suppressor ETS transcription factors and JUN-FOS at composite DNA sites

Many transcription factors regulate gene expression in a combinatorial fashion often by binding in close proximity on composite cis-regulatory DNA elements. Here we investigate the molecular basis by which ETS transcription factors bind with AP1 transcription factors JUN-FOS at composite DNA-binding sites. The ability to bind to DNA with JUN-FOS correlates with the phenotype of these proteins in prostate cancer: the oncogenic ERG and ETV1/4/5 subfamilies co-occupy ETS-AP1 sites with JUN-FOS in vitro, whereas JUN-FOS robustly inhibits DNA binding by the tumor suppressors EHF and SPDEF. EHF binds to ETS-AP1 DNA with tighter affinity than ERG in the absence of JUN-FOS, which may enable EHF to compete with ERG and JUN-FOS for binding to ETS-AP1 sites. Genome-wide mapping of EHF and ERG binding sites in a prostate epithelial cell line reveal that EHF is preferentially excluded from closely spaced ETS-AP1 DNA sequences. Structural modeling and mutational analyses indicate that adjacent positively-charged surfaces from EHF and JUN-FOS disfavor simultaneous DNA binding due to electrostatic repulsion. The conservation of positively charged residues on the JUN-FOS interface identified ELF1 as an additional ETS factor that exhibits anticooperative DNA binding, and we present evidence that ELF1 is frequently downregulated in prostate cancer. In summary, the divergence of electrostatic features of ETS factors at their JUN-FOS interface enables distinct binding events at ETS-AP1 DNA sequences. We propose that this mechanism can drive unique targeting of ETS transcription factors, thereby facilitating distinct transcriptional programs.

biochemistry↗

bioRxiv2017

ETV4 And AP1 Transcription Factors Form Multivalent Interactions With Three Sites On The MED25 Activator-Interacting Domain

The recruitment of transcriptional cofactors by sequence-specific transcription factors challenges the basis of high affinity and selective interactions. Extending previous studies that the N-terminal activation domain (AD) of ETV5 interacts with Mediator subunit 25 (MED25), we establish that similar, aromatic-rich motifs located both in the AD and in the DNA-binding domain (DBD) of the related ETS factor ETV4 interact with MED25. These ETV4 regions bind MED25 independently, display distinct kinetics, and combine to contribute to a high-affinity interaction of full-length ETV4 with MED25. Within the ETS family, high-affinity interactions with MED25 are specific for the ETV1/4/5 subfamily as other ETS factors display weaker or no detectable binding. The AD binds to a single site on MED25 and the DBD interacts with three MED25 sites, allowing for simultaneous binding of both domains in full-length ETV4. MED25 also stimulates the in vitro DNA binding activity of ETV4 by relieving autoinhibition. ETV1/4/5 factors are often overexpressed in prostate cancer and genome-wide studies in a prostate cancer cell line indicate that ETV4 and MED25 occupy enhancers that are enriched for ETS-binding sequences and are both functionally important for the transcription of genes regulated by these enhancers. AP1-binding sequences were observed in MED25-occupied regions and JUN/FOS also contact MED25; FOS strongly binds to the same MED25 site as ETV4 AD and JUN interacts with the other two MED25 sites. In summary, we describe features of the multivalent ETV4- and AP1-MED25 interactions, thereby implicating these factors in the recruitment of MED25 to transcriptional control elements.

biochemistry↗