A high G418-resistant neo(R) transgenic mouse and mouse embryonic fibroblast (MEF) feeder layers for cytotoxicity and gene targeting in vivo and in vitro

Identification of a GABAergic neural circuit governing leptin signaling deficiency-induced obesity

The hormone leptin is known to robustly suppress food intake by acting upon the leptin receptor (LepR) signaling system residing within the agouti-related protein (AgRP) neurons of the hypothalamus. However, clinical studies indicate that leptin is undesirable as a therapeutic regiment for obesity, which is at least partly attributed to the poorly understood complex secondary structure and key signaling mechanism of the leptin-responsive neural circuit. Here, we show that the LepR-expressing portal neurons send GABAergic projections to a cohort of α3-GABAA receptor expressing neurons within the dorsomedial hypothalamic nucleus (DMH) for the control of leptin-mediated obesity phenotype. We identified the DMH as a key brain region that contributes to the regulation of leptin-mediated feeding. Acute activation of the GABAergic AgRP-DMH circuit promoted food intake and glucose intolerance, while activation of post-synaptic MC4R neurons in the DMH elicited exactly opposite phenotypes. Rapid deletion of LepR from AgRP neurons caused an obesity phenotype which can be rescued by blockage of GABAA receptor in the DMH. Consistent with behavioral results, these DMH neurons displayed suppressed neural activities in response to hunger or hyperglycemia. Furthermore, we identified that α3-GABAA receptor signaling within the DMH exerts potent bi-directional regulation of the central effects of leptin on feeding and body weight. Together, our results demonstrate a novel GABAergic neural circuit governing leptin-mediated feeding and energy balance via a unique α3-GABAA signaling within the secondary leptin-responsive neural circuit, constituting a new avenue for therapeutic interventions in the treatment of obesity and associated comorbidities.

Antithymidylate resistance enables transgene selection and cell survival for T cells in the presence of 5-fluorouracil and antifolates

Antithymidylates (AThy) constitute a class of drugs used in the treatment of cancers such as lung, colon, breast and pancreas. These drugs inhibit DNA synthesis by targeting the enzymes dihydrofolate reductase (DHFR) and/or thymidylate synthase (TYMS). AThys effectively inhibit cancer cells, and also inhibit T cells, preventing anticancer immunity, which might otherwise develop from AThy-induced cancer destruction. We establish that T cells expressing mutant DHFR--DHFR L22F, F31S (DHFR(FS))--and/or mutant TYMS--TYMS T51S, G52S (TYMS(SS))-effectively survive in toxic concentrations of AThys methotrexate, pemetrexed and 5-fluorouracil. Furthermore, we show that DHFR(FS) permitted rapid selection of an inducible suicide transgene in T cells. These findings demonstrate that AThy resistances prevent AThy cytotoxicity to T cells while permitting selection of important transgenes. This technological development could enhance in vitro and in vivo survival and selection of T-cell therapeutics being designed for a broad range of cancers.

ECG in neonate mice with spinal muscular atrophy allows assessment of drug efficacy

Molecular technologies have produced diverse arrays of animal models for studying genetic diseases and potential therapeutics. Many have neonatal phenotypes. Spinal muscular atrophy (SMA) is a neuromuscular disorder primarily affecting children, and is of great interest in translational medicine. The most widely used SMA mouse models require all phenotyping to be performed in neonates since they do not survive much past weaning. Pre-clinical studies in neonate mice can be hindered by toxicity and a lack of quality phenotyping assays, since many assays are invalid in pups or require subjective scoring with poor inter-rater variability. We find, however, that passive electrocardiography (ECG) recording in conscious 11-day old SMA mice provides sensitive outcome measures, detecting large differences in heart rate, cardiac conduction, and autonomic control resulting from disease. We find significant drug benefits upon treatment with G418, an aminoglycoside targeting the underlying protein deficiency, even in the absence of overt effects on growth and survival. These findings provide several quantitative physiological biomarkers for SMA preclinical studies, and will be of utility to diverse disease models featuring neonatal cardiac arrhythmias.

The discovery of a reciprocal relationship between tyrosine-kinase signaling and cullin neddylation

While neddylation is known to activate cullin (CUL)-RING ubiquitin ligases (CRLs), its role in regulating T cell signaling is poorly understood. Using the investigational NEDD8 activating enzyme (NAE) inhibitor, MLN4924, we found that neddylation negatively regulates T cell receptor (TCR) signaling, as its inhibition increases IL-2 production, T cell proliferation and Treg development in vitro. We also discovered that loss of CUL neddylation occurs upon TCR signaling, and CRLs negatively regulate IL-2 production. Additionally, we found that tyrosine kinase signaling leads to CUL deneddylation in multiple cell types. These studies indicate that CUL neddylation is a global regulatory mechanism for tyrosine kinase signaling.