Exploring potential developmental origins of common neurodegenerative disorders.

In the United States, it is now estimated that 6.7 million people over the age of 65 are afflicted by Alzheimer's disease (AD), over 1 million people are living with Parkinson's disease (PD), and over 200 000 have or are at risk for developing Huntington's disease (HD). All three of these neurodegenerative diseases result in the ultimate death of distinct neuronal subtypes, and it is widely thought that age-related damage is the single biggest contributing factor to this neuronal death. However, recent studies are now suggesting that developmental defects during early neurogenesis could also play a role in the pathology of neurodegenerative diseases. Loss or overexpression of proteins associated with HD, PD, and AD also result in embryonic phenotypes but whether these developmental defects slowly unmask over time and contribute to age-related neurodegeneration remains highly debated. Here, we discuss known links between embryonic neurogenesis and neurodegenerative disorders (including common signaling pathways), potential compensatory mechanisms that could delay presentation of neurodegenerative disorders, and the types of model systems that could be used to study these links in vivo.

METTLing in Stem Cell and Cancer Biology.

The methyltransferase-like (METTL) family is a diverse group of methyltransferases that can methylate nucleotides, proteins, and small molecules. Despite this diverse array of substrates, they all share a characteristic seven-beta-strand catalytic domain, and recent evidence suggests many also share an important role in stem cell biology. The most well characterized family members METTL3 and METTL14 dimerize to form an N6-methyladenosine (m6A) RNA methyltransferase with established roles in cancer progression. However, new mouse models indicate that METTL3/METTL14 are also important for embryonic stem cell (ESC) development and postnatal hematopoietic and neural stem cell self-renewal and differentiation. METTL1, METTL5, METTL6, METTL8, and METTL17 also have recently identified roles in ESC pluripotency and differentiation, while METTL11A/11B, METTL4, METTL7A, and METTL22 have been shown to play roles in neural, mesenchymal, bone, and hematopoietic stem cell development, respectively. Additionally, a variety of other METTL family members are translational regulators, a role that could place them as important players in the transition from stem cell quiescence to differentiation. Here we will summarize what is known about the role of METTL proteins in stem cell differentiation and highlight the connection between their growing importance in development and their established roles in oncogenesis.

Membrane Stretch Gates NMDA Receptors.

NMDARs are ionotropic glutamate receptors widely expressed in the CNS, where they mediate phenomena as diverse as neurotransmission, information processing, synaptogenesis, and cellular toxicity. They function as glutamate-gated Ca2+-permeable channels, which require glycine as coagonist, and can be modulated by many diffusible ligands and cellular cues, including mechanical stimuli. Previously, we found that, in cultured astrocytes, shear stress initiates NMDAR-mediated Ca2+ entry in the absence of added agonists, suggesting that more than being mechanosensitive, NMDARs may be mechanically activated. Here, we used controlled expression of rat recombinant receptors and noninvasive on-cell single-channel current recordings to show that mild membrane stretch can substitute for the neurotransmitter glutamate in gating NMDAR currents. Notably, stretch-activated currents maintained the hallmark features of the glutamate-gated currents, including glycine-requirement, large unitary conductance, high Ca2+ permeability, and voltage-dependent Mg2+ blockade. Further, we found that the stretch-gated current required the receptor's intracellular domain. Our results are consistent with the hypothesis that mechanical forces can gate endogenous NMDAR currents even in the absence of synaptic glutamate release, which has important implications for understanding mechanotransduction and the physiological and pathologic effects of mechanical forces on cells of the CNS.SIGNIFICANCE STATEMENT We show that, in addition to enhancing currents elicited with low agonist concentrations, membrane stretch can gate NMDARs in the absence of the neurotransmitter glutamate. Stretch-gated currents have the principal hallmarks of the glutamate-gated currents, including requirement for glycine, large Na+ conductance, high Ca2+ permeability, and voltage-dependent Mg2+ block. Therefore, results suggest that mechanical forces can initiate cellular processes presently attributed to glutamatergic neurotransmission, such as synaptic plasticity and cytotoxicity. Given the ubiquitous presence of mechanical forces in the CNS, this discovery identifies NMDARs as possibly important mechanotransducers during development and across the lifespan, and during pathologic processes, such as those associated with traumatic brain injuries, shaken infant syndrome, and chronic traumatic encephalopathy.

Age-related neurodegeneration and cognitive impairments of NRMT1 knockout mice are preceded by misregulation of RB and abnormal neural stem cell development.

N-terminal methylation is an important posttranslational modification that regulates protein/DNA interactions and plays a role in many cellular processes, including DNA damage repair, mitosis, and transcriptional regulation. Our generation of a constitutive knockout mouse for the N-terminal methyltransferase NRMT1 demonstrated its loss results in severe developmental abnormalities and premature aging phenotypes. As premature aging is often accompanied by neurodegeneration, we more specifically examined how NRMT1 loss affects neural pathology and cognitive behaviors. Here we find that Nrmt1-/- mice exhibit postnatal enlargement of the lateral ventricles, age-dependent striatal and hippocampal neurodegeneration, memory impairments, and hyperactivity. These morphological and behavior abnormalities are preceded by alterations in neural stem cell (NSC) development. Early expansion and differentiation of the quiescent NSC pool in Nrmt1-/- mice is followed by its subsequent depletion and many of the resulting neurons remain in the cell cycle and ultimately undergo apoptosis. These cell cycle phenotypes are reminiscent to those seen with loss of the NRMT1 target retinoblastoma protein (RB). Accordingly, we find misregulation of RB phosphorylation and degradation in Nrmt1-/- mice, and significant de-repression of RB target genes involved in cell cycle. We also identify novel de-repression of Noxa, an RB target gene that promotes apoptosis. These data identify Nα-methylation as a novel regulatory modification of RB transcriptional repression during neurogenesis and indicate that NRMT1 and RB work together to promote NSC quiescence and prevent neuronal apoptosis.

CREB-mediated transcriptional activation of NRMT1 drives muscle differentiation.

The N-terminal methyltransferase NRMT1 is an important regulator of protein/DNA interactions and plays a role in many cellular processes, including mitosis, cell cycle progression, chromatin organization, DNA damage repair, and transcriptional regulation. Accordingly, loss of NRMT1 results in both developmental pathologies and oncogenic phenotypes. Though NRMT1 plays such important and diverse roles in the cell, little is known about its own regulation. To better understand the mechanisms governing NRMT1 expression, we first identified its predominant transcriptional start site and minimal promoter region with predicted transcription factor motifs. We then used a combination of luciferase and binding assays to confirm CREB1 as the major regulator of NRMT1 transcription. We tested which conditions known to activate CREB1 also activated NRMT1 transcription, and found CREB1-mediated NRMT1 expression was increased during recovery from serum starvation and muscle cell differentiation. To determine how NRMT1 expression affects myoblast differentiation, we used CRISPR/Cas9 technology to knock out NRMT1 expression in immortalized C2C12 mouse myoblasts. C2C12 cells depleted of NRMT1 lacked Pax7 expression and were unable to proceed down the muscle differentiation pathway. Instead, they took on characteristics of C2C12 cells that have transdifferentiated into osteoblasts, including increased alkaline phosphatase and type I collagen expression and decreased proliferation. These data implicate NRMT1 as an important downstream target of CREB1 during muscle cell differentiation.

Push-Dose Vasopressin for Hypotension in Septic Shock.

BACKGROUND: Peri-intubation cardiac arrest and hypotension in patients with septic shock occur often in the emergency department (ED) and ultimately lead to worse clinical outcomes. In recent years, the use of push-dose, or bolus-dose, vasopressors in the ED have become common practice for transient hypotension and bridging to continuous infusion vasopressors. Push-dose epinephrine and phenylephrine are the agents used most frequently in this scenario. CASE REPORT: A 63-year-old woman who was apneic and pulseless presented to our ED. After 4 min of cardiopulmonary resuscitation, spontaneous circulation was achieved, and the patient was intubated for airway protection. She became hypotensive with a blood pressure of 55/36 mm Hg. After receiving a 1-L bolus of lactated Ringer solution, she remained hypotensive with blood pressure of 80/51 mm Hg and a pulse of 129 beats/min. One unit of intravenous vasopressin push bolus was administered. Within 1 min, her hemodynamics improved to a blood pressure of 141/102 mm Hg and pulse of 120 beats/min. Over the next 2 h, her mean arterial pressure slowly and progressively declined from 120 to 80. No further vasoactive medications were required for approximately 120 min until norepinephrine and vasopressin was initiated for septic shock. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case report discusses the use of push-dose vasopressin as an alternate vasoactive medication to improve hemodynamics in a patient with vasodilatory septic shock.

Role of the PGE2 receptor subtypes EP1, EP2, and EP3 in repetitive traumatic brain injury.

AIMS: The goal was to explore the signaling pathways of PGE2 to investigate therapeutic effects against secondary injuries following TBI. METHODS: Young (4.9 ± 1.0 months) and aged (20.4 ± 1.4 months) male wild type (WT) C57BL/6 and PGE2 EP1, 2, and 3 receptor knockout mice were selected to either receive sham or repetitive concussive head injury. Immunohistochemistry protocols with Iba1 and GFAP were performed to evaluate microgliosis and astrogliosis in the hippocampus, two critical components of neuroinflammation. Passive avoidance test measured memory function associated with the hippocampus. RESULTS: No differences in hippocampal microgliosis were found when aged EP2-/- and EP3-/- mice were compared with aged WT mice. However, the aged EP1-/- mice had 69.2 ± 7.5% less hippocampal microgliosis in the contralateral hemisphere compared with WT aged mice. Compared with aged EP2-/- and EP3-/- , EP1-/- aged mice had 78.9 ± 5.1% and 74.7 ± 6.2% less hippocampal microgliosis in the contralateral hemisphere. Within the EP1-/- mice, aged mice had 90.7 ± 2.7% and 81.1 ± 5.6% less hippocampal microgliosis compared with EP1-/- young mice in the contralateral and ipsilateral hemispheres, respectively. No differences were noted in all groups for astrogliosis. There was a significant difference in latency time within EP1-/- , EP2-/- , and EP3-/- on day 1 and day 2 in aged and young mice. CONCLUSION: These findings demonstrate that the PGE2 EP receptors may be potential therapeutic targets to treat repetitive concussions and other acute brain injuries.

Aggressive Versus Conservative Initial Diuretic Dosing in the Emergency Department for Acute Decompensated Heart Failure.

BACKGROUND: Intravenous (IV) loop diuretics are recommended to relieve vascular congestion in patients with acute decompensated heart failure (ADHF); however, initial dosing is often empirical. Strong evidence supporting individualized diuretic dosing in the emergency department (ED) is lacking. OBJECTIVE: The purpose of this study was to compare the efficacy and safety of aggressive (≥2 daily home doses) and conservative (<2 daily home doses) initial doses of loop diuretic. METHODS: This was a retrospective cohort study in adult patients presenting to the ED with ADHF at an academic medical center from Apri 2015 to September 2015. The primary outcome was time to transition from IV to oral diuretics. RESULTS: A total of 91 patients were included (aggressive dosing, n = 44; conservative dosing, n = 47). Mean time to transition from IV to oral diuretics was 67.9 hours in the aggressive group compared with 88.1 hours in the conservative group ( P = 0.049). Mean hospital length of stay (LOS) was 119.5 hours in the aggressive group versus 123.0 hours in the conservative group ( P = 0.799). No differences were observed between the mean urine output ( P = 0.829), change in body weight ( P = 0.528), or serum creatinine ( P = 0.135). CONCLUSION: Patients who received an aggressive initial diuretic dose in the ED had a significantly faster time to oral diuretic therapy without any significant differences in hospital LOS, urine output, change in body weight, and renal function when compared with conservative dosing.

Comparative effectiveness of 3- versus 4-factor prothrombin complex concentrate for emergent warfarin reversal.

INTRODUCTION: Three- and 4-factor prothrombin complex concentrates (PCC) are routinely administered for emergent reversal of warfarin, but direct comparisons of clinical outcomes are lacking. The purpose of this study was to compare the safety and effectiveness of 3- and 4-PCC in patients requiring emergent warfarin reversal. MATERIALS AND METHODS: This was a single-center retrospective study in adult patients requiring administration of either 3-PCC or 4-PCC for emergent reversal of warfarin. RESULTS: One hundred sixty-five patients were included (3-PCC, n=109; 4-PCC, n=56). The most frequent indications for PCC were intracranial and gastrointestinal bleeding. Baseline median INR was 2.5 (2.0-3.2) and 2.4 (2.0-4.2) in the 3-PCC and 4-PCC groups. Thirty minutes after PCC administration, median INR decreased to 1.3 in both groups (p<0.001), and 87 (80%) versus 47 (84%) of patients had INR values≤1.5 (p=0.52) in the 3-PCC group versus the 4-PCC group. Thromboembolic events occurred in 7 patients (4%) and were similar between the 3-PCC (n=3, 3%) and 4-PCC (n=4, 7%) groups (p=0.23). Thirty-four (31%) patients in the 3-PCC group died compared to 5 patients (9%) in the 4-PCC group (p=0.001). INR>1.5 thirty minutes after PCC was associated with increased mortality (OR 4.3; 95% CI 1.8-10.4, p=0.001), and administration of a 4-PCC was associated with decreased mortality (OR 0.19; 95% CI 0.06-0.54, p=0.002). CONCLUSION: Patients who received 4-PCC, and those with INR≤1.5 regardless of type of PCC received were more likely to survive. Thromboembolic events were low in both groups and similar to previous studies.

Lack of association of the HMGA1 IVS5-13insC variant with type 2 diabetes in an ethnically diverse hypertensive case control cohort.

BACKGROUND: Recently, the high-mobility group A1 gene (HMGA1) variant IVS5-13insC has been associated with type 2 diabetes, but reported associations are inconsistent and data are lacking in Hispanic and African American populations. We sought to investigate the HMGA1-diabetes association and to characterize IVS5-13insC allele frequencies and linkage disequilibrium (LD) in 3,070 Caucasian, Hispanic, and African American patients from the INternational VErapamil SR-Trandolapril STudy (INVEST). METHODS: INVEST was a randomized, multicenter trial comparing two antihypertensive treatment strategies in an ethnically diverse cohort of hypertensive, coronary artery disease patients. Controls, who were diabetes-free throughout the study, and type 2 diabetes cases, either prevalent or incident, were genotyped for IVS5-13insC using Taqman®, confirmed with Pyrosequencing and Sanger sequencing. For LD analysis, genotyping for eight additional HMGA1 single nucleotide polymorphisms (SNPs) was performed using the Illumina® HumanCVD BeadChip. We used logistic regression to test association of the HMGA1 IVS5-13insC and diabetes, adjusted for age, gender, body mass index, and percentage European, African, and Native American ancestry. RESULTS: We observed IVS5-13insC minor allele frequencies consistent with previous literature in Caucasians and African Americans (0.03 in cases and 0.04 in controls for both race/ethnic groups), and higher frequencies in Hispanics (0.07 in cases and 0.07 in controls). The IVS5-13insC was not associated with type 2 diabetes overall (odds ratio 0.98 [0.76-1.26], p=0.88) or in any race/ethnic group. Pairwise LD (r2) of IVS5-13insC and rs9394200, a SNP previously used as a tag SNP for IVS5-13insC, was low (r2=0.47 in Caucasians, r2=0.25 in Hispanics, and r2=0.06 in African Americans). Furthermore, in silico analysis suggested a lack of functional consequences for the IVS5-13insC variant. CONCLUSIONS: Our results suggest that IVS5-13insC is not a functional variant and not associated with type 2 diabetes in an ethnically diverse, hypertensive, coronary artery disease population. Larger, more adequately powered studies need to be performed to confirm our findings.