Point-of-care testing, your cardiologist, and affairs of the heart

Background

Point-of-care testing (POCT) has applications across medical specialties and holds promise to improve patient care. While cardiovascular medicine has been attractive for POCT applications in recent years, little is known about how cardiovascular health professionals perceive them.

Objective

The objective of our study was to examine differences in perceptions and attitudes towards POCTs between cardiovascular health professionals compared to other healthcare professionals.

Methods

We surveyed healthcare professionals to assess perceptions of POCT usage and their benefits and concerns between October 2019 and March 2020. Questions regarding POCT perceptions were assessed on a 5-point Likert scale.

Results

We received a total of 148 survey responses; of the responders, 52% were male, 59% were physicians, and 50% worked in a hospital setting. We found that cardiology professionals were less likely, compared to other specialties, to view POCTs as improving patient management or reducing errors. These cardiology professionals were not constrained by resources or a lack of investment opportunities to implement these technologies.

Conclusion

This study provides a better understanding of perceptions about POCTs among healthcare specialists. To improve patient outcomes through the adoption and usage of POCTs, greater collaboration is advised among key industry and healthcare stakeholders.

The CD28 Transmembrane Domain Contains an Essential Dimerization Motif

CD28 plays a critical role in regulating immune responses both by enhancing effector T cell activation and differentiation and controlling the development and function of regulatory T cells. CD28 is expressed at the cell surface as a disulfide linked homodimer that is thought to bind ligand monovalently. How ligand binding triggers CD28 to induce intracellular signaling as well as the proximal signaling pathways that are induced are not well-understood. In addition, recent data suggest inside-out signaling initiated by the T cell antigen receptor can enhance CD28 ligand binding, possibly by inducing a rearrangement of the CD28 dimer interface to allow for bivalent binding. To understand how possible conformational changes during ligand-induced receptor triggering and inside-out signaling are mediated, we examined the CD28 transmembrane domain. We identified an evolutionarily conserved YxxxxT motif that is shared with CTLA-4 and resembles the transmembrane dimerization motif within CD3ζ. We show that the CD28 transmembrane domain can drive protein dimerization in a bacterial expression system at levels equivalent to the well-known glycophorin A transmembrane dimerization motif. In addition, ectopic expression of the CD28 transmembrane domain into monomeric human CD25 can drive dimerization in murine T cells as detected by an increase in FRET by flow cytometry. Mutation of the polar YxxxxT motif to hydrophobic leucine residues (Y145L/T150L) attenuated CD28 transmembrane mediated dimerization in both the bacterial and mammalian assays. Introduction of the Y145L/T150L mutation of the CD28 transmembrane dimerization motif into the endogenous CD28 locus by CRISPR resulted in a dramatic loss in CD28 cell surface expression. These data suggest that under physiological conditions the YxxxxT dimerization motif within the CD28 transmembrane domain plays a critical role in the assembly and/or expression of stable CD28 dimers at the cell surface.

A chromosome folding intermediate at the condensin-to-cohesin transition during telophase

Chromosome folding is modulated as cells progress through the cell cycle. During mitosis, condensins fold chromosomes into helical loop arrays. In interphase, the cohesin complex generates loops and topologically associating domains (TADs), while a separate process of compartmentalization drives segregation of active and inactive chromatin. We used synchronized cell cultures to determine how the mitotic chromosome conformation transforms into the interphase state. Using high-throughput chromosome conformation capture (Hi-C) analysis, chromatin binding assays and immunofluorescence, we show that, by telophase, condensin-mediated loops are lost and a transient folding intermediate is formed that is devoid of most loops. By cytokinesis, cohesin-mediated CTCF-CTCF loops and the positions of TADs emerge. Compartment boundaries are also established early, but long-range compartmentalization is a slow process and proceeds for hours after cells enter G1. Our results reveal the kinetics and order of events by which the interphase chromosome state is formed and identify telophase as a critical transition between condensin- and cohesin-driven chromosome folding.

The role of Runx2 in CD8+ T cell memory during acute LCMV Armstrong infection

During an acute viral infection, CD8+ T lymphocytes with T cell receptors (TCRs) specific for pathogen epitopes undergo clonal expansion and clear viral infection. After infection is cleared, the majority of the pathogen-specific CD8+ T cells undergo apoptosis, leaving a small population of memory CD8+ T cells that rapidly proliferate upon reinfection of the same antigen. How differentiation between the terminal effector cell population (TECs) and the memory cell population (MPECs) is regulated is not completely understood. Our research has focused on the role of the runt-related transcription factor Runx2 in CD8+ T cell memory formation during acute LCMV Armstrong infection. We have found using a mouse line with a T cell-specific deletion of Runx2 that loss of Runx2 leads to a defect in the formation of MPECs. We have also found that this defect is intrinsic to virus-specific CD8+ T cells. To further elucidate the upstream signaling pathways regulating Runx2 we have examined TCR signaling, cytokine signaling, and transcription factor regulation. These studies indicate that IRF4 levels inversely correlate with Runx2 expression in in vitro culture systems. We have also examined downstream pathways regulated by Runx2 in T cells, including gene expression and migration. This analysis has not revealed Runx2-dependent changes in gene expression in T cells isolated from LCMV-infected mice at D6 post-infection, nor in T cells stimulated in vitro; furthermore, we do not observe altered homing properties of Runx2-deficient T cells. Current studies are focused on examining Runx2 phosphorylation during memory CD8+ T cell differentiation. Overall, our data indicate an important role for Runx2 in CD8+ T cell memory during LCMV Armstrong infection.