PGE2 alters chromatin through H2A.Z-variant enhancer nucleosome modification to promote hematopoietic stem cell fate.

Prostaglandin E2 (PGE2) and 16,16-dimethyl-PGE2 (dmPGE2) are important regulators of hematopoietic stem and progenitor cell (HSPC) fate and offer potential to enhance stem cell therapies [C. Cutler et al. Blood 122, 3074-3081(2013); W. Goessling et al. Cell Stem Cell 8, 445-458 (2011); W. Goessling et al. Cell 136, 1136-1147 (2009)]. Here, we report that PGE2-induced changes in chromatin at enhancer regions through histone-variant H2A.Z permit acute inflammatory gene induction to promote HSPC fate. We found that dmPGE2-inducible enhancers retain MNase-accessible, H2A.Z-variant nucleosomes permissive of CREB transcription factor (TF) binding. CREB binding to enhancer nucleosomes following dmPGE2 stimulation is concomitant with deposition of histone acetyltransferases p300 and Tip60 on chromatin. Subsequent H2A.Z acetylation improves chromatin accessibility at stimuli-responsive enhancers. Our findings support a model where histone-variant nucleosomes retained within inducible enhancers facilitate TF binding. Histone-variant acetylation by TF-associated nucleosome remodelers creates the accessible nucleosome landscape required for immediate enhancer activation and gene induction. Our work provides a mechanism through which inflammatory mediators, such as dmPGE2, lead to acute transcriptional changes and modify HSPC behavior to improve stem cell transplantation.

Cardiopulmonary Resuscitation Outcomes and Trainee Perception of Code Status Discussions in Patients with Cirrhosis.

BACKGROUND: Cardiopulmonary resuscitation (CPR) outcomes among patients with cirrhosis are poor, but factors associated with outcomes and provider awareness remain under-evaluated. AIMS: We retrospectively investigated in-hospital CPR mortality among patients with cirrhosis, and, using these results, undertook an educational study among providers to improve knowledge of CPR outcomes and code status in patients with cirrhosis. METHODS: We identified patients with cirrhosis admitted from 2012 to 2022 who underwent CPR at our center; the primary outcome was survival-to-discharge. A brief video based on these results was presented online to Internal Medicine residents, along with paired pre/post-surveys assessing attitudes toward holding code status conversations and knowledge of CPR outcomes in patients with cirrhosis. RESULTS: 97 cases of CPR were identified. 27 patients (28%) survived to discharge post-CPR. A history of liver decompensation was significantly associated with lower survival (OR 0.21, p < 0.05). 22 residents participated in the educational intervention; afterward, their estimation of survival after CPR for patients with cirrhosis significantly improved (p < 0.05). Mean confidence in answering patient questions about prognosis, measured from 1 to 5, also significantly improved (2.4-"a little confident" vs. 3.8-"confident", p < 0.05). 59% of surveyed residents identified impact on liver transplant candidacy as at least a "somewhat significant" barrier to code status conversations. CONCLUSIONS: We identified significant trainee uncertainty about outcomes in patients with cirrhosis. These deficits improved after an educational intervention and gave providers more confidence in holding informed code status conversations with patients with cirrhosis, a population that faces barriers to adequate code discussions.

Functional chararacterization of the enzymes TabB and TabD involved in tabtoxin biosynthesis by Pseudomonas syringae.

Pseudomonas syringae pv. tabaci ATCC 11528 produces tabtoxin, a ß-lactam-containing dipeptide phytotoxin. Tabtoxinine-ß-lactam (TßL), one of tabtoxin's constituent amino acids, structurally mimics lysine, and many of the proteins encoded by the tabtoxin biosynthetic gene cluster are homologs of lysine biosynthetic enzymes, suggesting that the tabtoxin and lysine biosynthetic routes parallel one another. We cloned and expressed TabB and TabD, predicted homologs of tetrahydrodipicolinate (THDPA)-N-acyltransferase and N-acyl-THDPA aminotransferase, respectively, to determine their activities in vitro. We confirmed that TabB succinylates THDPA and that TabD is a PLP-dependent aminotransferase that utilizes glutamate as an amine donor. Surprisingly, we also found that though TabD could utilize the TabB product N-succinyl-THDPA as a substrate, THDPA itself was also recognized. These observations reveal that TabB functionally duplicates DapD, the THDPA-N-succinyltransferase involved in lysine biosynthesis, and reinforce the close relationship between the metabolic logics underpinning the respective biosynthetic pathways.

Transplantation-based screen identifies inducers of muscle progenitor cell engraftment across vertebrate species.

Stem cell transplantation presents a potentially curative strategy for genetic disorders of skeletal muscle, but this approach is limited by the deleterious effects of cell expansion in vitro and consequent poor engraftment efficiency. In an effort to overcome this limitation, we sought to identify molecular signals that enhance the myogenic activity of cultured muscle progenitors. Here, we report the development and application of a cross-species small-molecule screening platform employing zebrafish and mice, which enables rapid, direct evaluation of the effects of chemical compounds on the engraftment of transplanted muscle precursor cells. Using this system, we screened a library of bioactive lipids to discriminate those that could increase myogenic engraftment in vivo in zebrafish and mice. This effort identified two lipids, lysophosphatidic acid and niflumic acid, both linked to the activation of intracellular calcium-ion flux, which showed conserved, dose-dependent, and synergistic effects in promoting muscle engraftment across these vertebrate species.