HDAC3 ensures stepwise epidermal stratification via NCoR/SMRT-reliant mechanisms independent of its histone deacetylase activity.

Chromatin modifiers play critical roles in epidermal development, but the functions of histone deacetylases in this context are poorly understood. The class I HDAC, HDAC3, is of particular interest because it plays divergent roles in different tissues by partnering with tissue-specific transcription factors. We found that HDAC3 is expressed broadly in embryonic epidermis and is required for its orderly stepwise stratification. HDAC3 protein stability in vivo relies on NCoR and SMRT, which function redundantly in epidermal development. However, point mutations in the NCoR and SMRT deacetylase-activating domains, which are required for HDAC3's enzymatic function, permit normal stratification, indicating that HDAC3's roles in this context are largely independent of its histone deacetylase activity. HDAC3-bound sites are significantly enriched for predicted binding motifs for critical epidermal transcription factors including AP1, GRHL, and KLF family members. Our results suggest that among these, HDAC3 operates in conjunction with KLF4 to repress inappropriate expression of Tgm1, Krt16, and Aqp3 In parallel, HDAC3 suppresses expression of inflammatory cytokines through a Rela-dependent mechanism. These data identify HDAC3 as a hub coordinating multiple aspects of epidermal barrier acquisition.

Ethical Issues in Using Behavior Contracts to Manage the "Difficult" Patient and Family.

Long used as a tool for medical compliance and adhering to treatment plans, behavior contracts have made their way into the in-patient healthcare setting as a way to manage the "difficult" patient and family. The use of this tool is even being adopted by healthcare ethics consultants (HECs) in US hospitals as part of their work in navigating conflict at the bedside. Anecdotal evidence of their increasing popularity among clinical ethicists, for example, can be found at professional bioethics meetings and conversations and idea-sharing among practitioners on HEC social media. While there are a handful of papers gesturing toward a bioethical critique of behavior contracts of various types, the use of behavior contracts in the context of interpersonal conflict has not been vetted by bioethicists to determine their ethical legitimacy or efficacy. In this paper, we highlight a set of ethical concerns that we believe must be addressed before continuing or widespread implementation of behavior contracts to manage the "difficult" patient or family.

Modulation of Response Regulator CheY Reaction Kinetics by Two Variable Residues That Affect Conformation.

Microorganisms and plants utilize two-component systems to regulate adaptive responses to changing environmental conditions. Sensor kinases detect stimuli and alter their autophosphorylation activity accordingly. Signal propagation occurs via the transfer of phosphoryl groups from upstream kinases to downstream response regulator proteins. Removal of phosphoryl groups from the response regulator typically resets the system. Members of the same protein family may catalyze phosphorylation and dephosphorylation reactions with different efficiencies, exhibiting rate constants spanning many orders of magnitude to accommodate response time scales from milliseconds to days. We previously found that variable positions one or two residues to the C-terminal side of the conserved Asp phosphorylation site (D+2) or Thr/Ser (T+1/T+2) in response regulators alter reaction kinetics by direct interaction with phosphodonor or phosphoacceptor molecules. Here, we explore the kinetic effects of amino acid substitutions at the two positions immediately C-terminal to the conserved Lys (K+1/K+2) in the model Escherichia coli response regulator CheY. We measured CheY autophosphorylation and autodephosphorylation rate constants for 27 pairs of K+1/K+2 residues that represent 84% of naturally occurring response regulators. Effects on autodephosphorylation were modest, but autophosphorylation rate constants varied by 2 orders of magnitude, suggesting that the K+1/K+2 positions influence reaction kinetics by altering the conformational spectrum sampled by CheY at equilibrium. Additional evidence supporting this indirect mechanism includes the following: the effect on autophosphorylation rate constants is independent of the phosphodonor, the autophosphorylation rate constants and dissociation constants for the phosphoryl group analog BeF3- are inversely correlated, and the K+1/K+2 positions are distant from the phosphorylation site.IMPORTANCE We have identified five variable positions in response regulators that allow the rate constants of autophosphorylation and autodephosporylation reactions each to be altered over 3 orders of magnitude in CheY. The distributions of variable residue combinations across response regulator subfamilies suggest that distinct mechanisms associated with different variable positions allow reaction rates to be tuned independently during evolution for diverse biological purposes. This knowledge could be used in synthetic-biology applications to adjust the properties (e.g., background noise and response duration) of biosensors and may allow prediction of response regulator reaction kinetics from the primary amino acid sequence.

Rheb1 loss leads to increased hematopoietic stem cell proliferation and myeloid-biased differentiation in vivo.

Hematopoietic stem cells constitute a unique subpopulation of blood cells that can give rise to all types of mature cells in response to physiological demands. However, the intrinsic molecular machinery that regulates this transformative property remains elusive. In this paper, we demonstrate that small GTPase Rheb1 is a critical regulator of proliferation and differentiation of hematopoietic stem cells in vivo Rheb1 deletion led to increased phenotypic hematopoietic stem cell/hematopoietic progenitor cell proliferation under a steady state condition. Over-proliferating Rheb1-deficient hematopoietic stem cells were severely impaired in functional repopulation assays, and they failed to regenerate the blood system when challenged with hematopoietic ablation by sublethal irradiation. In addition, it was discovered that Rheb1 loss resulted in a lack of maturation of neutrophils / caused neutrophil immaturation by reducing mTORC1 activity, and that activation of the mTORC1 signaling pathway by mTOR activator 3BDO partially restored the maturation of Rheb1-deficient neutrophils. Rheb1 deficiency led to a progressive enlargement of the hematopoietic stem cell population and an eventual excessive myeloproliferation in vivo, including an overproduction of peripheral neutrophils and an excessive expansion of extramedullary hematopoiesis. Moreover, low RHEB expression was correlated with poor survival in acute myeloid leukemia patients with normal karyotype. Our results, therefore, demonstrate a critical and unique role for Rheb1 in maintaining proper hematopoiesis and myeloid differentiation.

Evaluating the Impact of the COVID-19 Pandemic on First-Year Medical Student Nutrition.

BACKGROUND: Medical school students in high-stress environments have been shown to make poor personal health decisions ranging from less healthy selections of food to lower rates of exercise. With the emergence of the COVID-19 pandemic adding a major social and health challenge, it is important to examine the effect this new stressor has on the health habits of medical school students. METHODS: All first-year students at Albany Medical College completed a self-recorded three-day log of food intake and exercise modality and duration. Reported data included calories, carbohydrates, protein, lipids, sodium, calcium, and other micronutrients. The data was divided between pre-pandemic (2018-19) and mid-pandemic (2020-21) entries. T-tests and ANOVA tests were used to compare for significance. RESULTS: Students consumed significantly fewer calories during the pandemic compared to before. This reduction was primarily driven by the female cohort of students. Specifically, this reduction in calories appears to be driven by a decrease in carbohydrate consumption, rather than lipids or protein, which did not change. Additionally, there were significant decreases in sodium, calcium, and vitamin D intake. The mid-pandemic time span (2020-21) appears to be correlated with decreased caloric intake, as well as other important nutrients such as vitamin D and calcium. CONCLUSIONS: This study demonstrated a decrease in calories, carbohydrates, sodium, and alcohol consumption when comparing pre- and mid-pandemic dietary habits of first-year medical students. It also indicated less than the recommended amount of calcium and Vitamin D consumption. Such changes may indicate restrictive eating habits in times of stress.

Will targeting PI3K/Akt/mTOR signaling work in hematopoietic malignancies?

The constitutive activation of phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway has been demonstrated to be critical in clinical cancer patients as well as in laboratory cancer models including hematological malignancies. Great efforts have been made to develop inhibitors targeting this pathway in hematological malignancies but so far the efficacies of these inhibitors were not as good as expected. By analyzing existing literatures and datasets available, we found that mutations of genes in the pathway only constitute a very small subset of hematological malignancies. Deep understanding of the function of gene, the pathway and/or its regulators, and the cellular response to inhibitors, may help us design better drugs targeting the hematological malignancies.