RATIONALE & OBJECTIVE:Distinguishing between transient and sustained subtypes of acute kidney injury (AKI) among hospitalized patients is valuable for clinical management and risk stratification. This study developed and validated a pragmatic electronic phenotype (e-phenotype) for the diagnosis, staging, and subtyping of AKI using electronic health record (EHR) data. STUDY DESIGN:Development of a computable rule-based algorithm to diagnose, stage, and subtype AKI using longitudinal changes of serum creatinine values recorded in an EHR. Assessment of the test characteristics of these algorithm-based diagnoses was implemented using a set of patients admitted to the emergency department (ED) with or without clinically diagnosed AKI. Validation of AKI diagnoses was implemented in 2 ways: using a set of patients hospitalized for COVID-19 and using a dataset of patients hospitalized for any cause following an ED visit. These analyses examined the associations of AKI stage and subtype with mortality. SETTING & PARTICIPANTS:Assessment of the test characteristics of the algorithm-based diagnoses: 90 ED visits for AKI and 376 visits without clinical evidence of AKI at Columbia University. Validation in the setting of COVID-19: EHR data from 117,514 instances of COVID-19 infection diagnosed at Columbia University Medical Center throughout the pandemic. Validation in the setting of general hospital admissions: 405,467 general hospital admissions at Beth Israel Medical Center in Boston, Massachusetts. TESTS COMPARED:The algorithm-based diagnosis, stage, and subtype of AKI were compared with the clinically adjudicated AKI diagnosis, stage, and subtype. OUTCOME:AKI detected, staged, and subtyped by an electronic algorithm, and 30-day mortality. RESULTS:The AKI e-phenotype had a positive predictive value of 95.4%, sensitivity of 69.0%, specificity of 99.2%, and overall accuracy of 93.4%. In COVID-19 patients, pre-existing CKD was an independent predictor of AKI. COVID-19-related AKI was associated with mortality in a stage-dependent manner. The subtype of sustained AKI was associated with higher mortality compared with transient AKI within and across all pandemic waves. These results were reproducible in the dataset of patients hospitalized for any condition. LIMITATIONS:Reliance on serum creatinine patterns alone and the inability to incorporate urine output or molecular markers to diagnose and subtype AKI. CONCLUSIONS:The AKI e-phenotype is accurate, scalable, and generalizable to diverse EHR datasets with reproducible associations with mortality. PLAIN-LANGAGE SUMMARY:Acute kidney injury (AKI) is a common and serious complication in hospitalized patients, but identifying and tracking it accurately in electronic health records is challenging. We developed an algorithm that uses patterns in kidney function test data to detect, classify, and distinguish AKI subtypes. After testing and validating the method, we applied it to 2 large hospital databases: one including patients hospitalized with COVID-19 and another including hospital admissions for any cause. Our approach reliably identified AKI and its association with poor outcomes. Patients with more severe or sustained AKI were more likely to die. This tool may help researchers study kidney injury more consistently across different health care settings.

Supplemental Table 1. List of DNA gene mutations tested in diagnostic tumor samples of our ALL cohort. Supplemental Table 2. List of 80 genes with RNA sequencing coverage. Supplemental Table 3. Demographics of 400 adult ALL cases. Supplemental Table 4. List of first-line (initial) therapies in Ph-positive B-ALL, Ph-negative B-ALL, and Tlineage ALL patients. Supplemental Table 5. Baseline gene rearrangements and structural variants of 329 molecularly characterized adult B-ALL patients. Supplemental Table 6. Baseline gene rearrangements and structural variants of 71 molecularly characterized adult T-lineage ALL patients. Supplemental Table 7. List of pathogenic/likely pathogenic germline variants in our ALL cohort. Supplementary Table 8. Multivariable analysis of overall survival (OS) in B-ALL patients. Supplemental Table 9. Clinical characteristics of patients studied in scDNA + protein sequencing experiments. Supplemental Table 10. Clinical characteristics of patients studied in scRNA-seq experiment. Supplemental Table 11. Ingenuity pathway analysis comparing B-lymphoblasts from B-ALL with MyM vs B-ALL without MyM.

ABSTRACTBackgroundAcute kidney injury (AKI) is a common complication of pediatric heart transplant, with a subset of patients developing severe AKI requiring dialysis (AKI‐D). We aimed to identify the epidemiology, risk factors, and outcomes of postoperative AKI‐D in pediatric heart transplant recipients.MethodsWe retrospectively identified all pediatric first‐time, single‐organ heart transplants at our institution from 2014 to 2022. Postoperative AKI was defined as AKI within 2 weeks of transplant. Unadjusted and adjusted logistic regression were used to identify characteristics associated with AKI‐D, and unadjusted time‐to‐event analyses were used to determine the association between AKI‐D and survival free of kidney failure.ResultsAmong 177 patients included, 116 (66%) developed postoperative AKI of any stage, including 13 (7%) who developed AKI‐D with median time from transplant to dialysis initiation of 6 days (IQR 3–13). In adjusted models, increased cardiopulmonary bypass time (OR 1.19, 95% CI 1.04–1.37, per 15 min increase in bypass time) and higher weight at transplant were associated with higher odds of AKI‐D, whereas patient demographics and pretransplant kidney function were not associated with AKI‐D. AKI‐D was associated with greater mortality during initial hospitalization (46% vs. 1%, p < 0.001) and a lower rate of survival free of kidney failure.ConclusionsThe incidence of AKI‐D after pediatric heart transplant was 7%, with extended cardiopulmonary bypass time associated with postoperative AKI‐D even in adjusted models. Further research is needed to improve the prediction and management of AKI‐D in this population.

Transcription factor (TF) DNA-binding dynamics govern cell fate and identity. However, our ability to pharmacologically control TF localization is limited. Here we leverage chemically driven binding site restriction leading to robust and DNA-sequence-specific redistribution of PU.1, a pioneer TF pertinent to many hematopoietic malignancies. Through an innovative technique, 'CLICK-on-CUT&Tag', we characterize the hierarchy of de novo PU.1 motifs, predicting occupancy in the PU.1 cistrome under binding site restriction. Temporal and single-molecule studies of binding site restriction uncover the pioneering dynamics of native PU.1 and identify the paradoxical activation of an alternate target gene set driven by PU.1 localization to second-tier binding sites. These transcriptional changes were corroborated by genetic blockade and site-specific reporter assays. Binding site restriction and subsequent PU.1 network rewiring causes primary human leukemia cells to differentiate. In summary, pharmacologically induced TF redistribution can be harnessed to govern TF localization, actuate alternate gene networks and direct cell fate.

Proximal tubule endocytosis is essential to produce protein free urine as well as to regulate system wide metabolic pathways, such as the activation of Vitamin D. We have determined that the proximal tubule expresses an endolysosomal membrane protein, protein spinster homolog1 (Spns1), which engenders a novel iron conductance that is indispensable during embryonic development. Conditional knockout of Spns1 with a novel Cre-LoxP construct specific to megalin-expressing cells led to the arrest of megalin receptor-mediated endocytosis as well as dextran pinocytosis in proximal tubules. The endocytic defect was accompanied by changes in megalin phosphorylation as well as enlargement of lysosomes confirming previous findings in Drosophila and Zebrafish. The endocytic defect was also accompanied by iron overload in proximal tubules. Remarkably, iron levels regulated the Spns1 phenotypes, because feeding an iron deficient diet or mating Spns1 knockout with divalent metal transporter1 (DMT1) knockout rescued the phenotypes. Conversely, iron loading wild type mice reproduced the endocytic defect, These data demonstrate a reversible, negative feedback for apical endocytosis, and raise the possibility that regulation of endocytosis, pinocytosis, megalin activation, and organellar size and function is nutrient-responsive.

Supplemental Figure 1. WHO/ICC subtypes for the B-ALL cohort. Supplemental Figure 2. Lymphoid clonal hematopoiesis (CH) mutations are less common in adults with ALL. Supplemental Figure 3. Blast percentage in the pre-treatment sample and detected variant allelic frequencies (VAF) of mutations in ALL patients with myeloid mutations. Supplemental Figure 4. Germline testing in the adult ALL cohort. Supplemental Figure 5. Associations of gene mutations and WHO/ICC disease subtypes in B-ALL. Supplemental Figure 6. Overall survival in adults with B-ALL. Supplemental Figure 7. Kaplan-Meier overall survival curves for Ph-negative B-ALL patients stratified based on the presence of TP53 and non-TP53 MyM (A), and treatment with different chemotherapy protocols (B, C, D). LH, low hypodiploidy. Supplemental Figure 8. T-lineage ALL with myeloid mutations (MyM). Supplemental Figure 9. Expression levels of lineage-specific surface markers. Supplemental Figure 10. Single cell DNA and protein sequencing to study the clonal architecture of Tlineage ALL with MyM. Supplemental Figure 11. A, Flow plots showing ETP-lymphoblast, myeloid, and mature lymphocytic compartments of ETP-ALL1, which were sorted for DNA extraction and sequencing. B, Distribution of variant allelic frequencies (VAFs) for myeloid (IDH2, DNMT3A) and NRAS mutations across subpopulations of cells in ETP-ALL1. Supplemental Figure 12. Clonal dynamics of ALL with MyM. Supplemental Figure 13. Two CH mutations (TP53 and DNMT3A) were detectable seven years before the diagnosis of therapy-related ALL22. Supplemental Figure 14. Clonal evolution of B-ALL2. Supplemental Figure 15. Lymphoblasts from B-ALL with MyM are characterized by their resistance to cytotoxic chemotherapy. Supplemental Figure 16. Curves showing viability of primary human B-ALL samples with TP53 mutation (n= 14), MyM (n= 16) and no MyM/TP53 (n= 24), treated with vincristine, doxorubicin, and blinatumomab at escalating doses. Supplemental Figure 17. Flow cytometry plots showing ALL22 (TP53-mutated B-ALL) sample treated with escalating doses of blinatumomab. Supplemental Figure 18. A, CR with MRD negativity rates in Ph-negative B-ALL patients treated with pediatric regimens, stratified based on age, gender, and treatment site. B, CR with MRD negativity rates in Ph-negative B-ALL patients treated with hyper-CVAD, stratified based on age, gender, and treatment site. C, CR with MRD negativity rates in Ph-negative B-ALL patients treated with inotuzumab. Supplemental Figure 19. A, MHC class I and II antigen expression in blasts from B-ALL with MyM vs B-ALL without MyM/TP53. B, Comparison of genes implicated in blinatumomab resistance in B-ALL with vs without MyM/TP53.

Abstract Myeloid neoplasms arise from preexisting clonal hematopoiesis (CH); however, the role of CH in the pathogenesis of acute lymphoblastic leukemia (ALL) is unknown. We found that 18% of adult ALL cases harbored TP53, and 16% had myeloid CH-associated gene mutations. ALL with myeloid mutations (MyM) had distinct genetic and clinical characteristics, associated with inferior survival. By using single-cell proteogenomic analysis, we demonstrated that myeloid mutations were present years before the diagnosis of ALL, and a subset of these clones expanded over time to manifest as dominant clones in ALL. Single-cell RNA sequencing revealed upregulation of genes associated with cell survival and resistance to apoptosis in B-ALL with MyM, which responds better to newer immunotherapeutic approaches. These findings define ALL with MyM as a high-risk disease that can arise from antecedent CH and offer new mechanistic insights to develop better therapeutic and preventative strategies. Significance: CH is a precursor lesion for lymphoblastic leukemogenesis. ALL with MyM has distinct genetic and clinical characteristics, associated with adverse survival outcomes after chemotherapy. CH can precede ALL years before diagnosis, and ALL with MyM is enriched with activated T cells that respond to immunotherapies such as blinatumomab. See related commentary by Iacobucci, p. 142.

Delayed graft function (DGF) is a frequent complication of kidney transplantation, but its impact on long- and short-term transplant outcomes is unclear. We conducted a systematic literature search for studies published from 2007 to 2020 investigating the association between DGF and posttransplant outcomes. Forest plots stratified between center studies and registry studies were created with pooled odds ratios. Posttransplant outcomes including graft failure, acute rejection, patient mortality, and kidney function were analyzed. Of the 3422 articles reviewed, 38 papers were included in this meta-analysis. In single-center studies, patients who experienced DGF had increased graft failure (odds ratio [OR] 3.38; 95% confidence interval [CI], 1.85-6.17; P < 0.01), acute allograft rejection (OR 1.84; 95% CI, 1.30-2.61; P < 0.01), and mortality (OR 2.32; 95% CI, 1.53-3.50; P < 0.01) at 1-y posttransplant. Registry studies showed increased graft failure (OR 3.66; 95% CI, 3.04-4.40; P < 0.01) and acute rejection (OR 3.24; 95% CI, 1.88-5.59; P < 0.01) but not mortality (OR 2.27; 95% CI, 0.97-5.34; P = 0.06) at 1-y posttransplant. DGF was associated with increased odds of graft failure, acute rejection, and mortality. These results in this meta-analysis could help inform the selection process, treatment, and monitoring of transplanted kidneys at high risk of DGF.

Aberrant transcriptional networks are hallmarks of aging and cancer, yet our ability to target these aberrations is poor. PU.1 is one such transcription factor (TF) who's transcriptional networks are corrupted in disease, including in >50% of Acute Myeloid Leukemia (AML) cases. In this study we investigate an unappreciated pharmacological approach to target the aberrant PU.1 network, by employing novel small molecules which competitively inhibit PU.1:DNA interactions. We performed an extensive multiomics-driven, molecular characterization of AML cells following exposure to PU.1-DNA binding inhibitors (e.g. DB2115). Unexpectedly, we found that such compounds not only led to a reduction of many canonical PU.1 transcripts, but also (seemingly paradoxically) caused increases in alternative PU.1-driven transcripts. We discovered that this two-sided response was a result of robust cistromic repositioning of PU.1 chromatin binding rather than global inhibition. From kinetic CUT&Tag and ATAC sequencing studies, we identified that PU.1 redistribution involved rapid PU.1 loss (~1hr) followed by delayed PU.1 gain (~4-12hrs), causing subsequent opening of the chromatin, thus demonstrating endogenous PU.1's powerful pioneering ability. Through development of CLICK-on-CUT&Tag, we identified exclusive drug binding at displaced PU.1 binding sites, and identified unique, sequence-specific ETS motifs dictating PU.1 gain or loss. By employing these motifs in eGFP reporter assays and CRISPRd systems, we identified direct PU.1-mediated transcriptional control of known and novel functionally relevant genes, including MYC, POMP and STRAP. Finally, we establish that primary AML samples are sensitive to pharmacological PU.1 redistribution upon exposure to DB2115, and the rewiring of the PU.1 network in these cells drives differentiation down the myeloid lineage (Figure 1). Overall, we uncover a novel biological phenomenon we describe as: Pharmacological transcription factor (TF) redistribution. “TF Redistributors”, such as DB2115 and next generation derivatives, are an unprecedented investigative and pharmacological tool which allow the study of complex and fast transcription factor dynamics without disrupting the structure or levels of the TF itself. Furthermore, we discover that pharmacological binding-site restriction and consecutive repositioning of the PU.1 network, cascades into an extensive rewiring of transcriptional circuits which ultimately drives myeloid differentiation of AML cells, potentially providing a novel therapeutic intervention for PU.1-corrupted AML.

Assessment of predonation glomerular filtration rate (GFR) is a key aspect of the evaluation of potential living kidney donors. In the United States, measurement of donor GFR is a regulatory requirement and most commonly assessed using 24-hour timed creatinine clearance (CrCl24), despite the potential for error due to incorrectly timed urine sample collection and tubular creatinine secretion.1,2 We aimed to determine the real-world performance of CrCl24 in living donor candidates.

Aptameric receptors are important biosensor components, yet our ability to identify them depends on the target structures. We analyzed the contributions of individual functional groups on small molecules to binding within 27 target-aptamer pairs, identifying potential hindrances to receptor isolation-for example, negative cooperativity between sterically hindered functional groups. To increase the probability of aptamer isolation for important targets, such as leucine and voriconazole, for which multiple previous selection attempts failed, we designed tailored strategies focused on overcoming individual structural barriers to successful selections. This approach enables us to move beyond standardized protocols into functional group-guided searches, relying on sequences common to receptors for targets and their analogs to serve as anchors in regions of vast oligonucleotide spaces wherein useful reagents are likely to be found.

Objectives: Dialysis is a well-established risk factor for morbidity and mortality after cardiovascular procedures. However, little is known regarding the outcomes of proximal aortic surgery in this high-risk cohort.Methods: Perioperative (in-hospital or 30-day mortality) and 10-year outcomes were analyzed for all the patients who underwent open proximal aortic repair with the diagnosis of nonruptured thoracic aortic aneurysm (aneurysm, n=325) or type A aortic dissection (dissection, n=461) from 1987 to 2015 using the US Renal Data System database.Results: In patients with aneurysm, perioperative mortality was 12.6%. The 10-year mortality was 81% +/- 3%. Age 65 years or more (hazard ratio [HR], 1.35; 95% con- fidence interval [CI], 1.03 to 1.78; P=.03), chronic obstructive pulmonary disease (HR, 1.68; 95% CI, 1.01-2.82; P=.047), and Black race (HR, 1.46; 95% CI, 1.09-1.97; P=.01) were independently associated with worse 10-year mortality. In patients with dissection, perioperative mortality was 24.3% and 10-year mortality was 87.9% +/- 2.2%. Age 65 years or more (HR, 1.49; 95% CI, 1.19-1.86; P <.001), conges- tive heart failure (HR, 1.39; 95% CI, 1.11-2.57; P=.004), and diabetes mellitus as the cause of dialysis (HR, 1.75; 95% CI, 1.2-2.57; P=.004) were independently associated with worse 10-year mortality. Black race (HR, 0.74; 95% CI, 0.6-0.92; P=.008) was associated with a better outcome.Conclusions: We described challenging perioperative and 10-year outcomes for dialysis patients undergoing proximal aortic repair. The present study suggests the need for careful patient selection in the elective repair of proximal aortic aneurysm for dialysis-dependent patients, whereas it affirms the feasibility of emergency surgery for acute type A aortic dissections. (J Thorac Cardiovasc Surg 2023;165:31-9)

A 77-year-old man with a history of cardiac transplantation and pulmonary tuberculosis was admitted for initiation of chemotherapy for multiple myeloma. His kidney function had worsened over several months, which was attributed to multiple myeloma–related kidney disease. Large bilateral kidney cysts precluded biopsy. Upon admission, he was found to have elevated gamma fraction and high IgG κ light chain levels. A peripheral smear showed over 20% plasma cells, diagnostic of progression from multiple myeloma to plasma cell leukemia. Medications included mycophenolate, tacrolimus, prednisone, metoprolol succinate, pantoprazole, and rifabutin-isoniazid-pyrazinamide-ethambutol. Vital signs were within normal limits. Physical exam demonstrated clear lungs and no peripheral edema and the chest radiograph demonstrated no pulmonary edema or pleural effusions. Table 1 outlines the patient’s laboratory studies during hospitalization.

The current strategy to detect acute injury of kidney tubular cells relies on changes in serum levels of creatinine. Yet serum creatinine (sCr) is a marker of both functional and pathological processes and does not adequately assay tubular injury. In addition, sCr may require days to reach diagnostic thresholds, yet tubular cells respond with programs of damage and repair within minutes or hours. To detect acute responses to clinically relevant stimuli, we created mice expressing Rosa26-floxed-stop uracil phosphoribosyltransferase (Uprt) and inoculated 4-thiouracil (4-TU) to tag nascent RNA at selected time points. Cre-driven 4-TU–tagged RNA was isolated from intact kidneys and demonstrated that volume depletion and ischemia induced different genetic programs in collecting ducts and intercalated cells. Even lineage-related cell types expressed different genes in response to the 2 stressors. TU tagging also demonstrated the transient nature of the responses. Because we placed Uprt in the ubiquitously active Rosa26 locus, nascent RNAs from many cell types can be tagged in vivo and their roles interrogated under various conditions. In short, 4-TU labeling identifies stimulus-specific, cell-specific, and time-dependent acute responses that are otherwise difficult to detect with other technologies and are entirely obscured when sCr is the sole metric of kidney damage.

Acute lymphoblastic leukemia (ALL) represents 20% of adult leukemias. Genomic risk stratification of ALL relies on the data generated from large cohorts of pediatric and young adult patients, where older patients with ALL have been underrepresented. It is imperative to understand the unique leukemogenic pathways in this group in order to develop novel therapeutic approaches. Clonal hematopoiesis (CH) is a precursor lesion for development of myeloid leukemias and mature lymphoid neoplasms (Niroula, Nat Med 2021), but its impact on the biology and outcomes of ALL is unknown. Based on our observations on high incidence of myeloid mutations in older adults with ALL, we hypothesized that CH constitutes a fertile genomic background for lymphoblastic leukemogenesis, and ALL with myeloid mutations is a unique entity with distinct clinical and molecular characteristics. We studied 400 adult patients with ALL treated at the University of Chicago, Moffitt Cancer Center, and City of Hope between 2014 and 2022 (Fig 1A). Genetic profiling of pre-treatment bone marrow samples was performed with a comprehensive panel covering 147 myeloid and lymphoid genes. Overall, 33% of ALL cases had at least one myeloid CH-associated mutation with the following frequencies: TP53 (18%), DNMT3A (5%), TET2 (4%), ASXL1 (3%), RUNX1 (3%), IDH2 (2%), BCORL1 (2%), U2AF1 (1%), CUX1 (1%), BCOR (1%), CBL (1%), and SF3B1 (1%). We further investigated the association between mutations and clinical variables by calculating the odds-ratios (OR) with adjustments for multiple testing by using the Benjamini-Hochberg method. Myeloid CH mutations in TP53, DNMT3A, TET2, and ASXL1 genes were more common in older adults with ALL. Mutations in TP53 and DNMT3A were enriched in therapy-related B-ALL group (OR 2.6, 95% CI= 1.3-5.5, q= .007 and OR 4.7, CI= 1.2-18.1, q= .01, respectively), and were more commonly associated with hypodiploid (OR 7.1, 95% CI= 1.5-32.7, q=.004 and OR 5.2, 95% CI= 0.6-48, q=.1, respectively) and hyperdiploid (OR 5.9, 95% CI= 2.7-13.1, q=<0.001 and OR 3.9, 95% CI= 1.1-16.5, q=.04, respectively) cytogenetics. We stratified the ALL cohort into three groups: TP53-mutated ALL, non-TP53 CH-associated ALL, and ALL without myeloid CH mutations. Patients in both groups of CH-associated B-ALL had worse overall survival (OS) than patients without myeloid CH mutations (median OS, 23 vs 25 vs 48 months, respectively, p=.001). In a multivariable analysis of OS for B-ALL, adjusting for age and therapy-related ALL, both TP53 (HR 1.95, 95% CI=1.2-3.17, p=.006) and non-TP53 myeloid CH (HR 1.95, 95% CI=1.14-3.35, p=.01) were associated with worse OS. Based on the data indicating high allelic frequencies of myeloid CH mutations in ALL, we hypothesized that these mutations are ancestral events arising in HSCs. To gain insights into the clonal architecture, we performed single cell DNA+protein sequencing using the Mission Bio, lnc platform. Data from 4,180 cells obtained from a CH-associated B-ALL patient are shown in Fig 1B. Cells were clustered by immunophenotype, and mutations were overlayed into 8 clusters. IDH2 R140Q mutation was shared between ALL and myeloid compartments. PTPN11 mutation was more prevalent in B-lymphoblasts. We observed a similar pattern in 7 additional patients, indicating that both lymphoblasts and non-malignant myeloid cells share CH mutations in ALL patients. Next, we investigated whether CH can be detected as a precursor lesion prior to ALL. In a patient with therapy-related B-ALL, a TET2 CH clone was detectable 5 years prior to ALL, and additional SF3B1 and CDKN2A mutations were detectable at the time of B-ALL diagnosis. We confirmed the presence of these mutations in B-lymphoblasts by single cell sequencing. This patient had persistent TET2/SF3B1 mutated CH despite achieving remission from B-ALL. We observed a similar pattern in four additional patients, for whom the CH mutations were detectable several years prior to their ALL diagnosis and were present in the dominant ALL clone. Collectively, these data support a model in which ALL can arise from pre-existing clones harboring myeloid CH mutations in a significant fraction of older adults. ALL with myeloid mutations is a distinct clinicopathologic entity with inferior survival outcomes. Future studies may decipher mechanisms driving lymphoid bias of CH-mediated leukemogenesis that can be targeted to prevent and treat ALL. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Coronary artery disease is highly prevalent in patients with end-stage renal disease (ESRD), and cardiovascular complications remain the most common cause of death in this patient population. Accordingly, many cardiac surgical procedures requiring cardiopulmonary bypass support are performed on these patients each year, with morbidity and mortality rates far exceeding patients without ESRD. Anuric patients lack the normal renal homeostatic functions which typically allow for physiologic protection from challenges during the operation, such as volume overload, hyperkalemia, and acidemia. Careful preoperative planning and coordination to provide pre-, intra-, and postoperative renal replacement therapies for such patients are imperative. Many different strategies have been reported in the literature. Zero-balance ultrafiltration is a newer strategy which utilizes convective ultrafiltration much like pre-filter continuous renal replacement therapy and utilizes pre-existing connections on the cardiopulmonary bypass pump performed by the perfusion team. This allows for control of potassium concentration throughout the operation with existing personnel and minimal additional equipment. Here, we describe the unique challenges caring for patients receiving renal replacement therapy undergoing cardiac surgical procedures requiring cardiopulmonary bypass.

Aberrant transcriptional networks are a hallmark of cancer, yet our knowledge of the intricacies of transcription factor behavior is poor. PU.1 is an ETS family transcription factor that is essential for hematopoiesis, however more than 50% of AML patients display a disruption of the PU.1 transcriptional network. In this study we implement novel molecular probes to competitively displace PU.1 from canonical DNA binding sites, allowing us to understand PU.1-chromatin binding dynamics, as well as identify the consequences of PU.1 binding site blockade upon PU.1-driven gene transcription and chromatin accessibility. We treated human PU.1low AML cells with a tool PU.1-DNA binding inhibitor, DB2115, and performed PU.1 CUT&Tag, ATAC sequencing and transcriptional profiling. We found, unexpectedly, that DB2115 not only led to inhibition of some canonical PU.1 targets but also mediated concurrent increases of other PU.1 targets. This two-sided response correlated strongly with a robust redistribution of PU.1 chromatin binding rather than a global inhibition - and included losses at regulatory regions of MYC, POMP and gains at CSF1R and TREM2. In fact, most of these redistributed sites (78% of PU.1 gained sites) display subsequent increases in chromatin accessibility and elevated target gene expression, highlighting the pioneering and transcriptional control exerted by repositioned PU.1. Kinetic analyses of PU.1 redistribution reveal that PU.1 losses occur rapidly after DB2115 exposure (1-4hrs), whereas PU.1 gains occur more slowly (4-12hrs) indicative of a loci searching phase prior to novel site binding. Development of an experimental approach combining CLICK-chemistry compound mapping with PU.1 CUT&Tag identified selective drug binding at displaced PU.1 binding sites compared to unchanged/gained sites, with both lost and gained regions being locally enriched for specific and distinct surrounding nucleotide sequences including A/T enrichment. Furthermore, CRISPR-dCas9 blockade and binding site-driven reporter investigations into specific PU.1 cistromic elements revealed important PU.1-mediated direct and rapid control of the POMP, CSF1R and STRAP genes. Overall, PU.1-DNA binding inhibition causes a robust perturbation of PU.1 transcriptional circuits via a novel phenomenon we describe as "Pharmacological transcription factor repositioning". Further investigations with binding site inhibitors such as these represent an unprecedented investigative approach to study complex and fast transcription factor dynamics without disrupting the structure or levels of the factor itself. Furthermore, exploitation of the pharmacological TF repositioning phenomenon may provide novel avenues for therapeutic intervention in PU.1-driven hematologic disorders and other transcriptionally-aberrant diseases.