The rockefeller university

Glucose is the ultimate substrate for most brain activities that use carbon, including synthesis of the neuro-transmitters glutamate and gamma-aminobutyric acid via mitochondrial tricarboxylic acid (TCA) cycle. Brain metabolism and neuronal excitability are thus interdependent. However, the principles that govern their relationship are not always intuitive because heritable defects of brain glucose metabolism are associated with the paradoxical coexistence, in the same individual, of episodic neuronal hyperexcitation (seizures) with reduced basal cerebral electrical activity. One such prototypic disorder is pyruvate dehydrogenase (PDH) deficiency (PDHD). PDH is central to metabolism because it steers most of the glucose-derived flux into the TCA cycle. To better understand the pathophysiology of PDHD, we generated mice with brain-specific reduced PDH activity that paralleled salient human disease features, including cerebral hypotrophy, decreased amplitude electroencephalogram (EEG), and epilepsy. The mice exhibited reductions in cerebral TCA cycle flux, glutamate content, spontaneous, and electrically evoked in vivo cortical field potentials and gamma EEG oscillation amplitude. Episodic decreases in gamma oscillations preceded most epileptiform discharges, facilitating their prediction. Fast-spiking neuron excitability was decreased in brain slices, contributing to in vivo action potential burst prolongation after whisker pad stimulation. These features were partially reversed after systemic administration of acetate, which augmented cerebral TCA cycle flux, glutamate-dependent synaptic transmission, inhibition and gamma oscillations, and reduced epileptiform discharge duration. Thus, our results suggest that dysfunctional excitability in PDHD is consequent to reduced oxidative flux, which leads to decreased neuronal activation and impaired inhibition, and can be mitigated by an alternative metabolic substrate.

Background/Aim: Invariant natural killer T-cells (iNKT) stimulated by CD1d-binding glycolipids have been shown to exert antitumor effects by a number of studies in a mouse model. Breast cancer is a devastating disease, with different types of breast cancer recurring locally or distant as metastatic/advanced disease following initial treatment. The aim of this study was to examine the tumoricidal effect of a CD1d-binding glycolipid, called 7DW8-5, against a highly invasive human breast cancer cell line both in vitro and in vivo. Materials and Methods: Parental MDA-MB-231 cells and MDA-MB-231 cells transduced with human CD1d were labeled with carboxyfluorescein diacetate succinimidyl ester (CFSE), followed by loading with glycolipids. After co-culturing with human iNKT cells, the cells were permeabilized and stained with Alexa Flour 647-conjugated antibody to active caspase-3, and analyzed using a BD LSR II. For the in vivo tumoricidal effect, MDA-MB-231 cells transduced with human CD1d and luciferase genes were injected into the mammary fat pad of female NOD/SCID/IL2r gamma null (NSG) mice, followed by the injection of human iNKT cells with or without 7DW8-5, and the levels of luminescence were analyzed with whole-body imaging. Results: Human iNKT cells could kill CD1d-expressing human breast cancer cells in vitro in the presence of 7DW8-5, but not a-GalCer. As for in vivo, the adoptive transfer of human iNKT cells into tumor-challenged NSG mice significantly inhibited the growth of CD1d+ MDA-MB-231 human breast cancer cells in the presence of 7DW8-5. Conclusion: CD1d-binding, glycolipid-based iNKT-cell therapy is suggested as a potent and effective treatment against breast cancer in humans.

RNA-binding proteins (RBPs) regulate genetic diversity, but the degree to which they do so in individual cell types in vivo is unknown. We developed NOVA2 cTag-crosslinking and immunoprecipitation (CLIP) to generate functional RBP-RNA maps from different neuronal populations in the mouse brain. Combining cell type datasets from Nova2-cTag and Nova2 conditional knockout mice revealed differential NOVA2 regulatory actions on alternative splicing (AS) on the same transcripts expressed in different neurons. This includes functional differences in transcripts expressed in cortical and cerebellar excitatory versus inhibitory neurons, where we find NOVA2 is required for, respectively, development of laminar structure, motor coordination, and synapse formation. We also find that NOVA2-regulated AS is coupled to NOVA2 regulation of intron retention in hundreds of transcripts, which can sequester the trans-acting splicing factor PTBP2. In summary, cTag-CLIP complements single-cell RNA sequencing (RNA-seq) studies by providing a means for understanding RNA regulation of functional cell diversity.

Although numerous epigenetic aberrancies accumulate in melanoma, their contribution to initiation and progression remain unclear. The epigenetic mark 5-hydroxymethylcytosine (5hmC), generated through TET-mediated DNA modification, is now referred to as the sixth base of DNA and has recently been reported as a potential biomarker for multiple types of cancer. Loss of 5hmC is an epigenetic hallmark of melanoma, but whether a decrease in 5hmc levels contributes directly to pathogenesis or whether it merely results from disease progression-associated epigenetic remodeling remains to be established. Here, we show that NRAS-driven melanomagenesis in mice is accompanied by an overall decrease in 5hmC and specific 5hmC gains in selected gene bodies. Strikingly, genetic ablation of Tet2 in mice cooperated with oncogenic NRASQ61K to promote melanoma initiation while suppressing specific gains in 5hmC. We conclude that TET2 acts as a barrier to melanoma initiation and progression, partly by promoting 5hmC gains in specific gene bodies. Significance: This work emphasizes the importance of epigenome plasticity in cancer development and highlights the involvement of druggable epigenetic factors in cancer.

Calcineurin is a calcium/calmodulin-regulated phosphatase known for its role in activation of T cells following engagement of the T cell receptor. Calcineurin inhibitors (CNIs) are widely used as immuno-suppressive agents; common adverse effects of CNIs are hypertension and hyperkalemia. While previous studies have implicated activation of the Na-Cl cotransporter (NCC) in the renal distal convoluted tubule (DCT) in this toxicity, the molecular mechanism of this effect is unknown. The renal effects of CNIs mimic the hypertension and hyperkalemia that result from germ-line mutations in with-no-lysine (WNK) kinases and the Kelch-like 3 (KLHL3)-CUL3 ubiquitin ligase complex. WNK4 is an activator of NCC and is degraded by binding to KLHL3 followed by WNK4's ubiquitylation and proteasomal degradation. This binding is prevented by phosphorylation of KLHL3 at serine 433 (KLHL3(S433-P)) via protein kinase C, resulting in increased WNK4 levels and increased NCC activity. Mechanisms mediating KLHL3(S433-P) dephosphorylation have heretofore been unknown. We now demonstrate that calcineurin expressed in DCT is a potent KLHL3(S433-P) phosphatase. In mammalian cells, the calcium ionophore ionomycin, a calcineurin activator, reduces KLHL3(S433-P) levels, and this effect is reversed by the calcineurin inhibitor tacrolimus and by siRNA-mediated knock-down of calcineurin. In vivo, tacrolimus increases levels of KLHL3(S433-P), resulting in increased levels of WNK4, phosphorylated SPAK, and NCC. Moreover, tacrolimus attenuates KLHL3-mediated WNK4 ubiquitylation and degradation, while this effect is absent in KLHL3 with S433A substitution. Additionally, increased extracellular K+ induced calcineurin-dependent dephosphorylation of KLHL3(S433-P). These findings demonstrate that KLHL3(S433-P) is a calcineurin substrate and implicate increased KLHL3 phosphorylation in tacrolimus-induced pathologies.

An important model for axon pathfinding is provided by guidance of embryonic commissural axons from dorsal spinal cord to ventral midline floor plate (FP). FP cells produce a chemoattractive activity, comprised largely of netrin1 (FP-netrin1) and Sonic hedgehog (Shh), that can attract the axons at a distance in vitro. netrin1 is also produced by ventricular zone (VZ) progenitors along the axons' route (VZ-netrin1). Recent studies using region-specific netrin1 deletion suggested that FP-netrin1 is dispensable and VZ-netrin1 sufficient for netrin guidance activity in vivo. We show that removing FP-netrin1 actually causes guidance defects in spinal cord consistent with long-range action (i.e., over hundreds of micrometers), and double mutant analysis supports that FP-netrin1 and Shh collaborate to attract at long range. We further provide evidence that netrin1 may guide via chemotaxis or haptotaxis. These results support the model that netrin1 signals at both short and long range to guide commissural axons in spinal cord.