William A. Alaynick

SnapShot: Spinal Cord Development

Hb9 Er81 Er81 Pea3 Ia propriospinals Hb9 Ils1Glutamate CA>2Cerebellum Somatosensory relayGlutamate IA>2Cerebellum Somatosensory relayGlutamate CA D>2 GABA Glycine I A>D>2INsF/E?GABA Glycine???Acetylcholine MuscleMuscleContraction of musculatureGlutamate ? ? Glutamate C A>D>2 MN, V1, V2RhythmicityGlutamate C A>D>2 MN, V1, V2Rhythmicity

Antipurinergic therapy corrects the autism-like features in the Fragile X (Fmr1 knockout) mouse model

BackgroundThis study was designed to test a new approach to drug treatment of autism spectrum disorders (ASDs) in the Fragile X (Fmr1) knockout mouse model.MethodsWe used behavioral analysis, mass spectrometry, metabolomics, electron microscopy, and western analysis to test the hypothesis that the disturbances in social behavior, novelty preference, metabolism, and synapse structure are treatable with antipurinergic therapy (APT).ResultsWeekly treatment with the purinergic antagonist suramin (20 mg/kg intraperitoneally), started at 9 weeks of age, restored normal social behavior, and improved metabolism, and brain synaptosomal structure. Abnormalities in synaptosomal glutamate, endocannabinoid, purinergic, and IP3 receptor expression, complement C1q, TDP43, and amyloid β precursor protein (APP) were corrected. Comprehensive metabolomic analysis identified 20 biochemical pathways associated with symptom improvements. Seventeen pathways were shared with human ASD, and 11 were shared with the maternal immune activation (MIA) model of ASD. These metabolic pathways were previously identified as functionally related mediators of the evolutionarily conserved cell danger response (CDR).ConclusionsThe data show that antipurinergic therapy improves the multisystem, ASD-like features of both the environmental MIA, and the genetic Fragile X models. These abnormalities appeared to be traceable to mitochondria and regulated by purinergic signaling.

Exercise and PGC-1α-Independent Synchronization of Type I Muscle Metabolism and Vasculature by ERRγ

How type I skeletal muscle inherently maintains high oxidative and vascular capacity in the absence of exercise is unclear. We show that nuclear receptor ERRγ is highly expressed in type I muscle and, when transgenically expressed in anaerobic type II muscles (ERRGO mice), dually induces metabolic and vascular transformation in the absence of exercise. ERRGO mice show increased expression of genes promoting fat metabolism, mitochondrial respiration, and type I fiber specification. Muscles in ERRGO mice also display an activated angiogenic program marked by myofibrillar induction and secretion of proangiogenic factors, neovascularization, and a 100% increase in running endurance. Surprisingly, the induction of type I muscle properties by ERRγ does not involve PGC-1α. Instead, ERRγ genetically activates the energy sensor AMPK in mediating the metabovascular changes in ERRGO mice. Therefore, ERRγ represents a previously unrecognized determinant that specifies intrinsic vascular and oxidative metabolic features that distinguish type I from type II muscle.

Nuclear Receptors, Mitochondria, and Lipid Metabolism

Lipid metabolism is a continuum from emulsification and uptake of lipids in the intestine to cellular uptake and transport to compartments such as mitochondria. Whether fats are shuttled into lipid droplets in adipose tissue or oxidized in mitochondria and peroxisomes depends on metabolic substrate availability, energy balance and endocrine signaling of the organism. Several members of the nuclear hormone receptor superfamily are lipid-sensing factors that affect all aspects of lipid metabolism. The physiologic actions of glandular hormones (e.g. thyroid, mineralocorticoid and glucocorticoid), vitamins (e.g. vitamins A and D) and reproductive hormones (e.g. progesterone, estrogen and testosterone) and their cognate receptors are well established. The peroxisome-proliferator activated receptors (PPARs) and liver X receptors (LXRs), acting in concert with PPARgamma Coactivator 1alpha (PGC-1alpha), have been shown to regulate insulin sensitivity and lipid handling. These receptors are the focus of intense pharmacologic studies to expand the armamentarium of small molecule ligands to treat diabetes and the metabolic syndrome (hypertension, insulin resistance, hyperglycemia, dyslipidemia and obesity). Recently, additional partners of PGC-1alpha have moved to the forefront of metabolic research, the estrogen-related receptors (ERRs). Although no endogenous ligands for these receptors have been identified, phenotypic analyses of knockout mouse models demonstrate an important role for these molecules in substrate sensing and handling as well as mitochondrial function.

Segregation of Axial Motor and Sensory Pathways via Heterotypic Trans-Axonal Signaling

Execution of motor behaviors relies on circuitries effectively integrating immediate sensory feedback to efferent pathways controlling muscle activity. It remains unclear how, during neuromuscular circuit assembly, sensory and motor projections become incorporated into tightly coordinated, yet functionally separate pathways. We report that, within axial nerves, establishment of discrete afferent and efferent pathways depends on coordinate signaling between coextending sensory and motor projections. These heterotypic axon-axon interactions require motor axonal EphA3/EphA4 receptor tyrosine kinases activated by cognate sensory axonal ephrin-A ligands. Genetic elimination of trans-axonal ephrin-A → EphA signaling in mice triggers drastic motor-sensory miswiring, culminating in functional efferents within proximal afferent pathways. Effective assembly of a key circuit underlying motor behaviors thus critically depends on trans-axonal signaling interactions resolving motor and sensory projections into discrete pathways.

Metabolic features of chronic fatigue syndrome

Significance Chronic fatigue syndrome is a multisystem disease that causes long-term pain and disability. It is difficult to diagnose because of its protean symptoms and the lack of a diagnostic laboratory test. We report that targeted, broad-spectrum metabolomics of plasma not only revealed a characteristic chemical signature but also revealed an unexpected underlying biology. Metabolomics showed that chronic fatigue syndrome is a highly concerted hypometabolic response to environmental stress that traces to mitochondria and was similar to the classically studied developmental state of dauer. This discovery opens a fresh path for the rational development of new therapeutics and identifies metabolomics as a powerful tool to identify the chemical differences that contribute to health and disease. More than 2 million people in the United States have myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). We performed targeted, broad-spectrum metabolomics to gain insights into the biology of CFS. We studied a total of 84 subjects using these methods. Forty-five subjects (n = 22 men and 23 women) met diagnostic criteria for ME/CFS by Institute of Medicine, Canadian, and Fukuda criteria. Thirty-nine subjects (n = 18 men and 21 women) were age- and sex-matched normal controls. Males with CFS were 53 (±2.8) y old (mean ± SEM; range, 21–67 y). Females were 52 (±2.5) y old (range, 20–67 y). The Karnofsky performance scores were 62 (±3.2) for males and 54 (±3.3) for females. We targeted 612 metabolites in plasma from 63 biochemical pathways by hydrophilic interaction liquid chromatography, electrospray ionization, and tandem mass spectrometry in a single-injection method. Patients with CFS showed abnormalities in 20 metabolic pathways. Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome. Pathway abnormalities included sphingolipid, phospholipid, purine, cholesterol, microbiome, pyrroline-5-carboxylate, riboflavin, branch chain amino acid, peroxisomal, and mitochondrial metabolism. Area under the receiver operator characteristic curve analysis showed diagnostic accuracies of 94% [95% confidence interval (CI), 84–100%] in males using eight metabolites and 96% (95% CI, 86–100%) in females using 13 metabolites. Our data show that despite the heterogeneity of factors leading to CFS, the cellular metabolic response in patients was homogeneous, statistically robust, and chemically similar to the evolutionarily conserved persistence response to environmental stress known as dauer.

Spinal Locomotor Circuits Develop Using Hierarchical Rules Based on Motorneuron Position and Identity

The coordination of multi-muscle movements originates in the circuitry that regulates the firing patterns of spinal motorneurons. Sensory neurons rely on the musculotopic organization of motorneurons to establish orderly connections, prompting us to examine whether the intraspinal circuitry that coordinates motor activity likewise uses cell position as an internal wiring reference. We generated a motorneuron-specific GCaMP6f mouse line and employed two-photon imaging to monitor the activity of lumbar motorneurons. We show that the central pattern generator neural network coordinately drives rhythmic columnar-specific motorneuron bursts at distinct phases of the locomotor cycle. Using multiple genetic strategies to perturb the subtype identity and orderly position of motorneurons, we found that neurons retained their rhythmic activity-but cell position was decoupled from the normal phasing pattern underlying flexion and extension. These findings suggest a hierarchical basis of motor circuit formation that relies on increasingly stringent matching of neuronal identity and position.

A role for dopamine in feeding responses produced by orexigenic agents

Dopamine-deficient (DD) mice become hypophagic and die of starvation by 3 to 4 weeks of age unless dopamine is restored by daily treatment with l-3-4-dihydroxyphenylalanine (l-dopa). We demonstrate here that DD mice mount qualitatively normal counter-regulatory blood glucose responses to insulin and 2-deoxy-d-glucose (2-DG). However, unlike control mice, DD mice fail to eat in response to acute glucoprivation induced by insulin or 2-DG. They also have a severely blunted response to central administration of peptide YY (PYY). Viral-mediated restoration of dopamine synthesis to the central caudate putamen (CPu) of DD mice rescues feeding and survival. However, this treatment fails to restore insulin- and 2-DG-induced feeding despite normalizing feeding in response to food deprivation and PYY. Since dopamine signaling in the CPu is not sufficient for glucoprivation-induced feeding, we propose that this feeding behavior may be mediated by dopamine in an anatomically distinct brain region.

Dependence of Hippocampal Function on ERRγ-Regulated Mitochondrial Metabolism

Neurons utilize mitochondrial oxidative phosphorylation (OxPhos) to generate energy essential for survival, function, and behavioral output. Unlike most cells that burn both fat and sugar, neurons only burn sugar. Despite its importance, how neurons meet the increased energy demands of complex behaviors such as learning and memory is poorly understood. Here we show that the estrogen-related receptor gamma (ERRγ) orchestrates the expression of a distinct neural gene network promoting mitochondrial oxidative metabolism that reflects the extraordinary neuronal dependence on glucose. ERRγ(-/-) neurons exhibit decreased metabolic capacity. Impairment of long-term potentiation (LTP) in ERRγ(-/-) hippocampal slices can be fully rescued by the mitochondrial OxPhos substrate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ in cerebral cortex and hippocampus exhibit defects in spatial learning and memory. These findings implicate neuronal ERRγ in the metabolic adaptations required for memory formation.

The effect of nap frequency on daytime sleep architecture

It is well documented that the quality and quantity of prior sleep influence future sleep. For instance, nocturnal sleep restriction leads to an increase in slow wave sleep (SWS) (i.e. SWS rebound) during a subsequent sleep period. However, few studies have examined how prior napping affects daytime sleep architecture. Because daytime naps are recommended for management of disrupted sleep, understanding the impact of napping on subsequent sleep may be important. We monitored sleep-wake patterns for one week with actigraphy followed by a 75-minute polysomnographically-recorded nap. We found that greater nap frequency was correlated with increased Stage 1 and decreased SWS. We categorized subjects based on nap frequency during the prior week (0 nap, 1 to 2 naps, and 3 to 4 naps) and found differences in Stage 1, Stage 2, and SWS between groups. Subjects who took no naps had the greatest amount of SWS, those who took 1 to 2 naps had the most Stage 2 sleep, and those who took 3 to 4 naps had the most Stage 1. While correlations were not found between nap frequency and nocturnal sleep measures, frequent napping was associated with increased subjective sleepiness. Therefore, frequent napping appears to be associated with lighter daytime sleep and increased sleepiness during the day. Speculatively, low levels of daytime sleepiness and increased SWS in non-nappers may help explain why these individuals choose not to nap.