Distinct roles of BRCA2 in replication fork protection in response to hydroxyurea and DNA interstrand cross-links.

DNA interstrand cross-links (ICLs) are a form of DNA damage that requires the interplay of a number of repair proteins including those of the Fanconi anemia (FA) and the homologous recombination (HR) pathways. Pathogenic variants in the essential gene BRCA2/FANCD1, when monoallelic, predispose to breast and ovarian cancer, and when biallelic, result in a severe subtype of Fanconi anemia. BRCA2 function in the FA pathway is attributed to its role as a mediator of the RAD51 recombinase in HR repair of programmed DNA double-strand breaks (DSB). BRCA2 and RAD51 functions are also required to protect stalled replication forks from nucleolytic degradation during response to hydroxyurea (HU). While RAD51 has been shown to be necessary in the early steps of ICL repair to prevent aberrant nuclease resection, the role of BRCA2 in this process has not been described. Here, based on the analysis of BRCA2 DNA-binding domain (DBD) mutants (c.8488-1G>A and c.8524C>T) discovered in FA patients presenting with atypical FA-like phenotypes, we establish that BRCA2 is necessary for the protection of DNA at ICLs. Cells carrying BRCA2 DBD mutations are sensitive to ICL-inducing agents but resistant to HU treatment consistent with relatively high HR repair in these cells. BRCA2 function at an ICL protects against DNA2-WRN nuclease-helicase complex and not the MRE11 nuclease that is implicated in the resection of HU-induced stalled replication forks. Our results also indicate that unlike the processing at HU-induced stalled forks, the function of the SNF2 translocases (SMARCAL1, ZRANB3, or HLTF), implicated in fork reversal, are not an integral component of the ICL repair, pointing to a different mechanism of fork protection at different DNA lesions.

A Dominant Mutation in Human RAD51 Reveals Its Function in DNA Interstrand Crosslink Repair Independent of Homologous Recombination.

Repair of DNA interstrand crosslinks requires action of multiple DNA repair pathways, including homologous recombination. Here, we report a de novo heterozygous T131P mutation in RAD51/FANCR, the key recombinase essential for homologous recombination, in a patient with Fanconi anemia-like phenotype. In vitro, RAD51-T131P displays DNA-independent ATPase activity, no DNA pairing capacity, and a co-dominant-negative effect on RAD51 recombinase function. However, the patient cells are homologous recombination proficient due to the low ratio of mutant to wild-type RAD51 in cells. Instead, patient cells are sensitive to crosslinking agents and display hyperphosphorylation of Replication Protein A due to increased activity of DNA2 and WRN at the DNA interstrand crosslinks. Thus, proper RAD51 function is important during DNA interstrand crosslink repair outside of homologous recombination. Our study provides a molecular basis for how RAD51 and its associated factors may operate in a homologous recombination-independent manner to maintain genomic integrity.

Biomarker-Based Assessment for Infectious Risk Before and After Heart Transplantation.

PURPOSE OF REVIEW: Survival outcomes for heart transplant recipients have improved in recent decades, but infection remains a significant cause of morbidity and mortality. In this review, we discuss several biological markers, or biomarkers, that may be used to monitor immunologic status in this patient population. RECENT FINDINGS: While modest, data on the utility of immune biomarkers in heart transplant recipients suggest correlation between low level of immune response and increased infection risk. More novel assays, such as the detection of circulating levels of pathogen cell-free DNA in plasma and the use of Torque teno virus load as a surrogate for net state of immunosuppression, have potential to be additional important biomarkers. Biomarker approaches to individualize immunosuppression therapy among heart transplant recipients is a promising area of medicine. However, additional studies are needed to inform the optimal protocol in which to incorporate these biomarkers into clinical practice.

Engineering the genome of Thermus thermophilus using a counterselectable marker.

UNLABELLED: Thermus thermophilus is an extremely thermophilic bacterium that is widely used as a model thermophile, in large part due to its amenability to genetic manipulation. Here we describe a system for the introduction of genomic point mutations or deletions using a counterselectable marker consisting of a conditionally lethal mutant allele of pheS encoding the phenylalanyl-tRNA synthetase α-subunit. Mutant PheS with an A294G amino acid substitution renders cells sensitive to the phenylalanine analog p-chlorophenylalanine. Insertion of the mutant pheS allele via a linked kanamycin resistance gene into a chromosomal locus provides a gene replacement intermediate that can be removed by homologous recombination using p-chlorophenylalanine as a counterselective agent. This selection is suitable for the sequential introduction of multiple mutations to produce a final strain unmarked by an antibiotic resistance gene. We demonstrated the utility of this method by constructing strains bearing either a point mutation in or a precise deletion of the rrsB gene encoding 16S rRNA. We also used this selection to identify spontaneous, large-scale deletions in the pTT27 megaplasmid, apparently mediated by either of the T. thermophilus insertion elements ISTth7 and ISTth8. One such deletion removed 121 kb, including 118 genes, or over half of pTT27, including multiple sugar hydrolase genes, and facilitated the development of a plasmid-encoded reporter system based on ß-galactosidase. The ability to introduce mutations ranging from single base substitutions to large-scale deletions provides a potentially powerful tool for engineering the genome of T. thermophilus and possibly other thermophiles as well. IMPORTANCE: Thermus thermophilus is an extreme thermophile that has played an important part in the development of both biotechnology and basic biological research. Its suitability as a genetic model system is established by its natural competence for transformation, but the scarcity of genetic tools limits the kinds of manipulations that can currently be performed. We have developed a counterselectable marker that allows the introduction of unmarked deletions and point mutations into the T. thermophilus genome. We find that this marker can also be used to select large chromosomal deletions apparently resulting from aberrant transposition of endogenous insertion sequences. This system has the potential to advance the genetic manipulation of this important model organism.

US population qualifying for aspirin use for primary prevention of cardiovascular disease.

Objective: Aspirin has been used for primary prevention of atherosclerotic cardiovascular disease (ASCVD) for decades, but this indication has become controversial with recent trial data. The 2022 US Preventive Services Task Force (USPSTF) provided a recommendation to consider aspirin use for primary prevention in adults 40-59 years with a 10-year ASCVD risk ≥10 % and not at increased risk of bleeding, yet population estimates for the impact of this recommendation are unknown. The objective of this study is to determine the prevalence and demographics of the US population who meet eligibility criteria for aspirin under the new 2022 USPSTF guidelines. Methods: This is a serial cross-sectional study using data from the 2011-March 2020 National Health and Nutrition Examination Survey (NHANES) database. Individuals aged 40-59 years without a self-reported history of ASCVD were included. 10-year estimated ASCVD risk ≥10 % as calculated by the Pooled Cohort Equations (PCE) and increased bleeding risk determined using variables adapted from USPSTF guidelines were further applied as inclusion and exclusion criteria, respectively. The weighted frequencies of US adults aged 40-59 years qualifying for primary prevention aspirin, subgrouped by gender, age, and race/ethnicity, were calculated. Results: Among 72,840,734 US individuals aged 40-59 years, 7.2 million (10 %) are eligible for consideration of primary prevention aspirin by PCE criteria. Of these, approximately 30 % would be potentially excluded based on increased bleeding risks, resulting in a net eligible cohort of 5 million. This represents 7 % of US adults aged 40-59 years and only 2.6 % of adults ≥18 years. Men, age 50-59 years, and Black race have higher proportions meeting aspirin use eligibility. Conclusions: The overall prevalence of US individuals who qualify for aspirin for primary prevention under the 2022 USPSTF guidelines is modest, with larger proportional eligibility among men, older age, and Black individuals.

Molecular adsorption steers bacterial swimming at the air/water interface.

Microbes inhabiting Earth have adapted to diverse environments of water, air, soil, and often at the interfaces of multiple media. In this study, we focus on the behavior of Caulobacter crescentus, a singly flagellated bacterium, at the air/water interface. Forward swimming C. crescentus swarmer cells tend to get physically trapped at the surface when swimming in nutrient-rich growth medium but not in minimal salt motility medium. Trapped cells move in tight, clockwise circles when viewed from the air with slightly reduced speed. Trace amounts of Triton X100, a nonionic surfactant, release the trapped cells from these circular trajectories. We show, by tracing the motion of positively charged colloidal beads near the interface that organic molecules in the growth medium adsorb at the interface, creating a high viscosity film. Consequently, the air/water interface no longer acts as a free surface and forward swimming cells become hydrodynamically trapped. Added surfactants efficiently partition to the surface, replacing the viscous layer of molecules and reestablishing free surface behavior. These findings help explain recent similar studies on Escherichia coli, showing trajectories of variable handedness depending on media chemistry. The consistent behavior of these two distinct microbial species provides insights on how microbes have evolved to cope with challenging interfacial environments.

Asymptomatic Apical Hypertrophic Cardiomyopathy in an Elite Competitive Athlete.

A 17-year-old male elite athlete presented for evaluation after an abnormal pre-competitive college screening electrocardiogram. Subsequent evaluation revealed the presence of hypertrophic cardiomyopathy. He remained asymptomatic throughout four years of follow-up. Through shared decision making, he continued to play competitively and is now a professional athlete. (Level of Difficulty: Advanced.).

Predictors of Hemodynamic Response to Intra-Aortic Balloon Pump Therapy in Patients With Acute Decompensated Heart Failure and Cardiogenic Shock.

OBJECTIVES: There is renewed interest in intra-aortic balloon pump (IABP) use in chronic systolic heart failure (HF) patients with acute decompensation and cardiogenic shock (CS). We sought to identify predictors of early IABP response to guide optimal use in this population. METHODS: We retrospectively analyzed records of chronic systolic HF patients presenting to our center between 2011-2018 with acute decompensated HF who received IABP for CS. An IABP responder was defined as having both an early cardiac output (CO) increase and mean pulmonary artery pressure (MPAP) decrease above the cohort median values. RESULTS: During this period, a total of 218 chronic systolic HF patients received IABP for acute decompensation with CS. The average CO increase was 0.57 ± 0.85 L/min and MPAP reduction was 5.1 ± 7.6 mm Hg. Fifty-six patients (25.7%) were identified as IABP responders, with mean CO increase of 1.21 ± 0.87 L/min and MPAP reduction of 12.1 ± 5.9 mm Hg. Systemic vascular resistance (SVR) >1300 dynes/sec/cm-5 (odds ratio [OR], 5.04; 95% confidence interval [CI], 1.86-13.6; P<.01) and moderate-severe mitral regurgitation (OR, 2.42; 95% CI, 1.25-4.66; P<.01) predicted robust hemodynamic response. CONCLUSIONS: A subset of chronic systolic HF patients had robust hemodynamic response to IABP with significant CO augmentation and MPAP reduction. Higher SVR and moderate-severe mitral regurgitation predicted early hemodynamic response to IABP.

An Instrumented Ultrasound Probe for Shear Wave Elastography With Uneven Force Distribution.

An instrumented ultrasound probe system is designed to estimate the distribution of pressure applied across the probe face during image acquisition. The pressure distribution is used to investigate the effects of varying, and non-uniform, pressure distributions on shear wave elastography measurements in phantoms and ex vivo samples. Pressure distribution has a notable effect on shear wave elastography of ex vivo samples. The gradient in applied pressure across the probe face is mirrored in the gradient of elasticity measurements across the ultrasound elastogram image.

Comparison of the Hemodynamic Response to Intra-Aortic Balloon Counterpulsation in Patients With Cardiogenic Shock Resulting from Acute Myocardial Infarction Versus Acute Decompensated Heart Failure.

The intra-aortic balloon pump (IABP) neither benefits nor harms patients with acute myocardial infarction (AMI) with cardiogenic shock (CS) but may stabilize those with chronic heart failure who decompensate into CS. We sought to compare its hemodynamic effects in these 2 populations. We performed a retrospective analysis of the hemodynamic effects of IABP for AMI or acute decompensated heart failure (ADHF) patients with hemodynamic evidence of CS. The primary outcome was cardiac output (CO) change following insertion. In total, 205 patients were treated for CS resulting from AMI (73; 35.6%) or ADHF (132; 64.4%). At baseline, both cohorts had significant hemodynamic compromise with mean arterial pressure 75.6 ± 12.3 mm Hg, CO 3.02 ± 0.84 L/min, and cardiac power index 0.26 ± 0.06 W/m2; these parameters were nearly identical between groups though ADHF-CS patients had a higher pre-IABP mean pulmonary artery (PA) pressure than AMI-CS patients. After IABP insertion, ADHF-CS patients had moderate CO augmentation whereas AMI-CS experienced almost no improvement (0.58 ± 0.79 L/min vs 0.12 ± 1.00 L/min; p = 0.0009). Intracardiac filling pressures were reduced by similar amounts in both cohorts. Systemic vascular resistance was reduced in patients with ADHF-CS but not in those with AMI-CS. In conclusion, following IABP insertion, ADHF-CS patients experience roughly a 5-fold greater CO augmentation compared with AMI-CS patients. Pre-IABP PA pressure differences and differential systemic vascular resistance reduction may explain these results and shed light on recent evidence supporting IABP use in ADHF-CS and curbing it in AMI-CS.

Real-Time Blood Pressure Estimation From Force-Measured Ultrasound.

OBJECTIVE: Our objective is to create a blood pressure measurement device, which may provide a way to easily acquire frequent measurements. Common techniques to measure blood pressure include an arterial catheter, an oscillometric pressure cuff, or an auscultatory pressure cuff. METHODS: The approach takes as input ultrasound images of an artery and contact force between the ultrasound array and subject. A subject may perform the self-measurements. Image and force data is analyzed for its quality and used to provide guidance or reject poor measurements. Tissue motions, due to probe contact forces and pulsing blood pressure, are estimated from the ultrasound image. Tissues elasticities and blood pressure are found by optimally fitting the observed tissue motion versus applied forces to a table of predicted motion-pre-generated with a finite element tissue deformation model. The output of the optimization is an estimate of systolic and diastolic blood pressure, arterial stiffness, and surrounding tissue stiffness. RESULTS: The real-time implementation of the algorithm was validated on a cohort of 21 single-visit volunteers and on four volunteers self-monitored longitudinally. The systolic and diastolic pressures were compared to oscillometric cuff readings. Regression and Bland-Altman analyses were performed. CONCLUSION: Systolic pressure and diastolic pressure can be estimated in real-time and by the subject using this novel non-invasive ultrasound-based method (systolic accuracy/precision: -5.2 mmHg/10.7 mmHg; diastolic accuracy/precision: -3.9/8.0 mmHg). SIGNIFICANCE: The method occupies a middle ground between the arterial catheter and cuff-based techniques. It has the potential to give calibration-free results.