Publications by authors named "Russell Ray"

20 Publications

  • Page 1 of 1

Intermittent Hypoxia and Effects on Early Learning/Memory: Exploring the Hippocampal Cellular Effects of Pediatric Obstructive Sleep Apnea.

Anesth Analg 2021 07;133(1):93-103

Department of Anesthesiology.

This review provides an update on the neurocognitive phenotype of pediatric obstructive sleep apnea (OSA). Pediatric OSA is associated with neurocognitive deficits involving memory, learning, and executive functioning. Adenotonsillectomy (AT) is presently accepted as the first-line surgical treatment for pediatric OSA, but the executive function deficits do not resolve postsurgery, and the timeline for recovery remains unknown. This finding suggests that pediatric OSA potentially causes irreversible damage to multiple areas of the brain. The focus of this review is the hippocampus, 1 of the 2 major sites of postnatal neurogenesis, where new neurons are formed and integrated into existing circuitry and the mammalian center of learning/memory functions. Here, we review the clinical phenotype of pediatric OSA, and then discuss existing studies of OSA on different cell types in the hippocampus during critical periods of development. This will set the stage for future study using preclinical models to understand the pathogenesis of persistent neurocognitive dysfunction in pediatric OSA.
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http://dx.doi.org/10.1213/ANE.0000000000005273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8134503PMC
July 2021

Somatotopic Organization and Intensity Dependence in Driving Distinct NPY-Expressing Sympathetic Pathways by Electroacupuncture.

Neuron 2020 11 12;108(3):436-450.e7. Epub 2020 Aug 12.

Dana-Farber Cancer Institute and Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

The neuroanatomical basis behind acupuncture practice is still poorly understood. Here, we used intersectional genetic strategy to ablate NPY noradrenergic neurons and/or adrenal chromaffin cells. Using endotoxin-induced systemic inflammation as a model, we found that electroacupuncture stimulation (ES) drives sympathetic pathways in somatotopy- and intensity-dependent manners. Low-intensity ES at hindlimb regions drives the vagal-adrenal axis, producing anti-inflammatory effects that depend on NPY adrenal chromaffin cells. High-intensity ES at the abdomen activates NPY splenic noradrenergic neurons via the spinal-sympathetic axis; these neurons engage incoherent feedforward regulatory loops via activation of distinct adrenergic receptors (ARs), and their ES-evoked activation produces either anti- or pro-inflammatory effects due to disease-state-dependent changes in AR profiles. The revelation of somatotopic organization and intensity dependency in driving distinct autonomic pathways could form a road map for optimizing stimulation parameters to improve both efficacy and safety in using acupuncture as a therapeutic modality.
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http://dx.doi.org/10.1016/j.neuron.2020.07.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7666081PMC
November 2020

Off-Target Effects of Clozapine-N-Oxide on the Chemosensory Reflex Are Masked by High Stress Levels.

Front Physiol 2019 22;10:521. Epub 2019 May 22.

Memory Brain Research Center, Baylor College of Medicine, Houston, TX, United States.

Respiratory chemosensory circuits are implicated in several physiological and behavioral disorders ranging from sudden infant death syndrome to panic disorder. Thus, a comprehensive map of the chemosensory network would be of significant value. To delineate chemosensory neuronal populations, we have utilized pharmacogenetic Designer Receptors Exclusively Activated by Designer Drugs (DREADD) perturbations for acute neuronal perturbations in respiratory circuit mapping. Recent studies show that the biologically inert DREADD ligand clozapine-N-oxide (CNO) is back-metabolized into the bioactive compound clozapine in rodents, emphasizing the need for CNO-only DREADD-free controls, which have been carried out in several studies. However, we show that high CNO doses used in several chemosensory circuit mapping studies nonetheless affect the chemosensory ventilatory reflexes in control mice, which is unmasked by extensive habituation. Here, unhabituated control animals showed no differences in respiratory parameters after CNO administration, whereas habituated animals receiving the commonly used dose of 10 mg/kg of CNO show a deficit in the hypercapnic (high CO) chemosensory reflex, which is not present in 1 mg/kg CNO treated or saline control groups. Our findings indicate that even in appropriately controlled studies, additional masked CNO off-target effects may exist and underscore the importance of using minimal doses of activating ligand in combination with high levels of habituation.
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http://dx.doi.org/10.3389/fphys.2019.00521DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6538678PMC
May 2019

Follicle-stimulating hormone and luteinizing hormone increase Ca2+ in the granulosa cells of mouse ovarian follicles†.

Biol Reprod 2019 08;101(2):433-444

Department of Cell Biology, UConn Health, Farmington, CT, USA.

In mammalian ovarian follicles, follicle stimulating hormone (FSH) and luteinizing hormone (LH) signal primarily through the G-protein Gs to elevate cAMP, but both of these hormones can also elevate Ca2+ under some conditions. Here, we investigate FSH- and LH-induced Ca2+ signaling in intact follicles of mice expressing genetically encoded Ca2+ sensors, Twitch-2B and GCaMP6s. At a physiological concentration (1 nM), FSH elevates Ca2+ within the granulosa cells of preantral and antral follicles. The Ca2+ rise begins several minutes after FSH application, peaks at ∼10 min, remains above baseline for another ∼10 min, and depends on extracellular Ca2+. However, suppression of the FSH-induced Ca2+ increase by reducing extracellular Ca2+ does not inhibit FSH-induced phosphorylation of MAP kinase, estradiol production, or the acquisition of LH responsiveness. Like FSH, LH also increases Ca2+, when applied to preovulatory follicles. At a physiological concentration (10 nM), LH elicits Ca2+ oscillations in a subset of cells in the outer mural granulosa layer. These oscillations continue for at least 6 h and depend on the activity of Gq family G-proteins. Suppression of the oscillations by Gq inhibition does not inhibit meiotic resumption, but does delay the time to 50% ovulation by about 3 h. In summary, both FSH and LH increase Ca2+ in the granulosa cells of intact follicles, but the functions of these Ca2+ rises are only starting to be identified.
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http://dx.doi.org/10.1093/biolre/ioz085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7302518PMC
August 2019

Embryonic hindbrain patterning genes delineate distinct cardio-respiratory and metabolic homeostatic populations in the adult.

Sci Rep 2017 08 22;7(1):9117. Epub 2017 Aug 22.

Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA.

Previous studies based on mouse genetic mutations suggest that proper partitioning of the hindbrain into transient, genetically-defined segments called rhombomeres is required for normal respiratory development and function in neonates. Less clear is what role these genes and the neurons they define play in adult respiratory circuit organization. Several Cre drivers are used to access and study developmental rhombomeric domains (Eng1 , HoxA2-Cre, Egr2 , HoxB1 , and HoxA4-Cre) in the adult. However, these drivers show cumulative activity beyond the brainstem while being used in intersectional genetic experiments to map central respiratory circuitry. We crossed these drivers to conditional DREADD mouse lines to further characterize the functional contributions of Cre defined populations. In the adult, we show that acute DREADD inhibition of targeted populations results in a variety of not only respiratory phenotypes but also metabolic and temperature changes that likely play a significant role in the observed respiratory alterations. DREADD mediated excitation of targeted domains all resulted in death, with unique differences in the patterns of cardio-respiratory failure. These data add to a growing body of work aimed at understanding the role of early embryonic patterning genes in organizing adult respiratory homeostatic networks that may be perturbed in congenital pathophysiologies.
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http://dx.doi.org/10.1038/s41598-017-08810-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5567350PMC
August 2017

() defines neurons that are required for full hypercapnic and hypoxic reflexes.

Biol Open 2017 Aug 15;6(8):1200-1208. Epub 2017 Aug 15.

Baylor College of Medicine, Department of Neuroscience, 1 Baylor Plaza, T707, Houston, TX 77030, USA

The catecholaminergic (CA) system has been implicated in many facets of breathing control and offers an important target to better comprehend the underlying etiologies of both developmental and adult respiratory pathophysiologies. Here, we used a noninvasive DREADD-based pharmacogenetic approach to acutely perturb ()-defined neurons in awake and unrestrained mice in an attempt to characterize CA function in breathing. We report that clozapine-N-oxide (CNO)-DREADD-mediated inhibition of -defined neurons results in blunted ventilatory responses under respiratory challenge. Under a hypercapnic challenge (5% CO/21% O/74% N), perturbation of neurons results in reduced f, [Formula: see text] and [Formula: see text] Under a hypoxic challenge (10% O/90% N), we saw reduced f, [Formula: see text] and [Formula: see text], in addition to instability in both interbreath interval and tidal volume, resulting in a Cheyne-Stokes-like respiratory pattern. These findings demonstrate the necessity of -defined neurons for the hypercapnic and hypoxic ventilatory responses and breathing stability during hypoxia. However, given the expanded non-CA expression domains of the mouse line found in the brainstem, full phenotypic effect cannot be assigned solely to CA neurons. Nonetheless, this work identifies a key respiratory population that may lead to further insights into the circuitry that maintains respiratory stability in the face of homeostatic challenges.
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http://dx.doi.org/10.1242/bio.026823DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5576086PMC
August 2017

Respiratory Network Stability and Modulatory Response to Substance P Require Nalcn.

Neuron 2017 Apr 6;94(2):294-303.e4. Epub 2017 Apr 6.

Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA; Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA; Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030, USA; Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Baylor College of Medicine, Houston, TX 77030, USA. Electronic address:

Respiration is a rhythmic activity as well as one that requires responsiveness to internal and external circumstances; both the rhythm and neuromodulatory responses of breathing are controlled by brainstem neurons in the preBötzinger complex (preBötC) and the retrotrapezoid nucleus (RTN), but the specific ion channels essential to these activities remain to be identified. Because deficiency of sodium leak channel, non-selective (Nalcn) causes lethal apnea in humans and mice, we investigated Nalcn function in these neuronal groups. We found that one-third of mice lacking Nalcn in excitatory preBötC neurons died soon after birth; surviving mice developed apneas in adulthood. Interestingly, in both preBötC and RTN neurons, the Nalcn current influences the resting membrane potential, contributes to maintenance of stable network activity, and mediates modulatory responses to the neuropeptide substance P. These findings reveal Nalcn's specific role in both rhythmic stability and responsiveness to neuropeptides within the respiratory network.
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http://dx.doi.org/10.1016/j.neuron.2017.03.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702257PMC
April 2017

A low cost, simplified, and scaleable pneumotachograph and face mask for neonatal mouse respiratory measurements.

J Pharmacol Toxicol Methods 2017 Jul 15;86:1-11. Epub 2017 Feb 15.

Baylor College of Medicine, Department of Neuroscience, Room T703, 1 Baylor Plaza, Houston, TX 77030, United States. Electronic address:

Introduction: Neonatal respiratory disorders are a leading cause of perinatal mortality due to complications resulting from premature births and prenatal exposure to drugs of abuse, but optimal treatments for these symptoms are still unclear due to a variety of confounds and risk factors. Mouse models present an opportunity to study the underlying mechanisms and efficacy of potential treatments of these conditions with controlled variables. However, measuring respiration in newborn mice is difficult and commercial components are expensive and often require modification, creating a barrier and limiting our understanding of the short and long-term effects of birth complications on respiratory function.

Methods: Here, we present an inexpensive and simple flow through pneumotachograph and face mask design that can be easily scaled for parallel, high-throughput assays measuring respiration in neonatal mouse pups. The final apparatus consists of three main parts: a water-jacketed chamber, an integrated support tray for the pup, and a pneumotachograph consisting of a two side-arm air channel that is attached to a pressure transducer.

Results: The pneumotach showed a linear response and clean, steady respiratory traces in which apneas and sighs were clearly visible. Administration of caffeine in P0.5 CD1 wildtype neonates resulted in an increase in tidal volume, minute ventilation, and minute ventilation normalized to oxygen consumption as well as a decrease in periodic instability.

Discussion: The described methods offer a relatively simple and inexpensive approach to constructing a pneumotachograph for non-invasive measurements of neonatal mouse respiration, enhancing accessibility and enabling the high-throughput and parallel characterizations of neonatal respiratory disorders and potential pharmacological therapies.
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http://dx.doi.org/10.1016/j.vascn.2017.02.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5684870PMC
July 2017

Lethal lung hypoplasia and vascular defects in mice with conditional Foxf1 overexpression.

Biol Open 2016 Nov 15;5(11):1595-1606. Epub 2016 Nov 15.

Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA

FOXF1 heterozygous point mutations and genomic deletions have been reported in newborns with the neonatally lethal lung developmental disorder, alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). However, no gain-of-function mutations in FOXF1 have been identified yet in any human disease conditions. To study the effects of FOXF1 overexpression in lung development, we generated a Foxf1 overexpression mouse model by knocking-in a Cre-inducible Foxf1 allele into the ROSA26 (R26) locus. The mice were phenotyped using micro-computed tomography (micro-CT), head-out plethysmography, ChIP-seq and transcriptome analyses, immunohistochemistry, and lung histopathology. Thirty-five percent of heterozygous R26-Lox-Stop-Lox (LSL)-Foxf1 embryonic day (E)15.5 embryos exhibit subcutaneous edema, hemorrhages and die perinatally when bred to Tie2-cre mice, which targets Foxf1 overexpression to endothelial and hematopoietic cells. Histopathological and micro-CT evaluations revealed that R26Foxf1; Tie2-cre embryos have immature lungs with a diminished vascular network. Neonates exhibited respiratory deficits verified by detailed plethysmography studies. ChIP-seq and transcriptome analyses in E18.5 lungs identified Sox11, Ghr, Ednrb, and Slit2 as potential downstream targets of FOXF1. Our study shows that overexpression of the highly dosage-sensitive Foxf1 impairs lung development and causes vascular abnormalities. This has important clinical implications when considering potential gene therapy approaches to treat disorders of FOXF1 abnormal dosage, such as ACDMPV.
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http://dx.doi.org/10.1242/bio.019208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5155529PMC
November 2016

Generation of Two Noradrenergic-Specific Dopamine-Beta-Hydroxylase-FLPo Knock-In Mice Using CRISPR/Cas9-Mediated Targeting in Embryonic Stem Cells.

PLoS One 2016 21;11(7):e0159474. Epub 2016 Jul 21.

Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America.

CRISPR/Cas9 mediated DNA double strand cutting is emerging as a powerful approach to increase rates of homologous recombination of large targeting vectors, but the optimization of parameters, equipment and expertise required remain barriers to successful mouse generation by single-step zygote injection. Here, we sought to apply CRISPR/Cas9 methods to traditional embryonic stem (ES) cell targeting followed by blastocyst injection to overcome the common issues of difficult vector construction and low targeting efficiency. To facilitate the study of noradrenergic function, which is implicated in myriad behavioral and physiological processes, we generated two different mouse lines that express FLPo recombinase under control of the noradrenergic-specific Dopamine-Beta-Hydroxylase (DBH) gene. We found that by co-electroporating a circular vector expressing Cas9 and a locus-specific sgRNA, we could target FLPo to the DBH locus in ES cells with shortened 1 kb homology arms. Two different sites in the DBH gene were targeted; the translational start codon with 6-8% targeting efficiency, and the translational stop codon with 75% targeting efficiency. Using this approach, we established two mouse lines with DBH-specific expression of FLPo in brainstem catecholaminergic populations that are publically available on MMRRC (MMRRC_041575-UCD and MMRRC_041577-UCD). Altogether, this study supports simplified, high-efficiency Cas9/CRISPR-mediated targeting in embryonic stem cells for production of knock-in mouse lines in a wider variety of contexts than zygote injection alone.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0159474PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4956144PMC
July 2017

Translational control of nicotine-evoked synaptic potentiation in mice and neuronal responses in human smokers by eIF2α.

Elife 2016 Mar 1;5. Epub 2016 Mar 1.

Department of Neuroscience, Baylor College of Medicine, Houston, United States.

Adolescents are particularly vulnerable to nicotine, the principal addictive component driving tobacco smoking. In a companion study, we found that reduced activity of the translation initiation factor eIF2α underlies the hypersensitivity of adolescent mice to the effects of cocaine. Here we report that nicotine potentiates excitatory synaptic transmission in ventral tegmental area dopaminergic neurons more readily in adolescent mice compared to adults. Adult mice with genetic or pharmacological reduction in p-eIF2α-mediated translation are more susceptible to nicotine's synaptic effects, like adolescents. When we investigated the influence of allelic variability of the Eif2s1 gene (encoding eIF2α) on reward-related neuronal responses in human smokers, we found that a single nucleotide polymorphism in the Eif2s1 gene modulates mesolimbic neuronal reward responses in human smokers. These findings suggest that p-eIF2α regulates synaptic actions of nicotine in both mice and humans, and that reduced p-eIF2α may enhance susceptibility to nicotine (and other drugs of abuse) during adolescence.
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http://dx.doi.org/10.7554/eLife.12056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4786418PMC
March 2016

Activity of Raphé Serotonergic Neurons Controls Emotional Behaviors.

Cell Rep 2015 Dec 19;13(9):1965-76. Epub 2015 Nov 19.

Department of Psychiatry, Columbia University, New York, NY 10032, USA; New York State Psychiatric Institute, New York, NY 10032, USA. Electronic address:

Despite the well-established role of serotonin signaling in mood regulation, causal relationships between serotonergic neuronal activity and behavior remain poorly understood. Using a pharmacogenetic approach, we find that selectively increasing serotonergic neuronal activity in wild-type mice is anxiogenic and reduces floating in the forced-swim test, whereas inhibition has no effect on the same measures. In a developmental mouse model of altered emotional behavior, increased anxiety and depression-like behaviors correlate with reduced dorsal raphé and increased median raphé serotonergic activity. These mice display blunted responses to serotonergic stimulation and behavioral rescues through serotonergic inhibition. Furthermore, we identify opposing consequences of dorsal versus median raphé serotonergic neuron inhibition on floating behavior, together suggesting that median raphé hyperactivity increases anxiety, whereas a low dorsal/median raphé serotonergic activity ratio increases depression-like behavior. Thus, we find a critical role of serotonergic neuronal activity in emotional regulation and uncover opposing roles of median and dorsal raphé function.
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http://dx.doi.org/10.1016/j.celrep.2015.10.061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756479PMC
December 2015

It's not the heart: autonomic nervous system predisposition to lethal ventricular arrhythmias.

Heart Rhythm 2015 Nov 8;12(11):2294-5. Epub 2015 Jul 8.

Cardiovascular Research Institute; Department of Molecular Physiology and Biophysics; Department of Medicine (Cardiology), Baylor College of Medicine, Houston, Texas. Electronic address:

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http://dx.doi.org/10.1016/j.hrthm.2015.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5103306PMC
November 2015

Egr2-neurons control the adult respiratory response to hypercapnia.

Brain Res 2013 May 19;1511:115-25. Epub 2012 Dec 19.

Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.

`The early growth response 2 transcription factor, Egr2, establishes a population of brainstem neurons essential for normal breathing at birth. Egr2-null mice die perinatally of respiratory insufficiency characterized by subnormal respiratory rate and severe apneas. Here we bypass this lethality using a noninvasive pharmacogenetic approach to inducibly perturb neuron activity postnatally, and ask if Egr2-neurons control respiration in adult mice. We found that the normal ventilatory increase in response to elevated tissue CO₂ was impaired, blunted by 63.1 ± 8.7% after neuron perturbation due to deficits in both respiratory amplitude and frequency. By contrast, room-air breathing was unaffected, suggesting that the drive for baseline breathing may not require those Egr2-neurons manipulated here. Of the multiple brainstem sites proposed to affect ventilation in response to hypercapnia, only the retrotrapezoid nucleus, a portion of the serotonergic raphé, and a portion of the A5 nucleus have a history of Egr2 expression. We recently showed that acute inhibition of serotonergic neurons en masse blunts the CO₂ chemoreflex in adults, causing a difference in hypercapnic response of ∼50% after neuron perturbation through effects on respiratory amplitude only. The suppressed respiratory frequency upon perturbation of Egr2-neurons thus may stem from non-serotonergic neurons within the Egr2 domain. Perturbation of Egr2-neurons did not affect body temperature, even on exposure to ambient 4°C. These findings support a model in which Egr2-neurons are a critical component of the respiratory chemoreflex into adulthood. Methodologically, these results highlight how pharmacogenetic approaches allow neuron function to be queried in unanesthetized adult animals, reaching beyond the roadblocks of developmental lethality and compensation as well as the anatomical disturbances associated with invasive methods. This article is part of a Special Issue entitled Optogenetics (7th BRES).
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http://dx.doi.org/10.1016/j.brainres.2012.12.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3947592PMC
May 2013

GABAergic RIP-Cre neurons in the arcuate nucleus selectively regulate energy expenditure.

Cell 2012 Oct;151(3):645-57

Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA.

Neural regulation of energy expenditure is incompletely understood. By genetically disrupting GABAergic transmission in a cell-specific fashion, and by combining this with selective pharmacogenetic activation and optogenetic mapping techniques, we have uncovered an arcuate-based circuit that selectively drives energy expenditure. Specifically, mice lacking synaptic GABA release from RIP-Cre neurons have reduced energy expenditure, become obese and are extremely sensitive to high-fat diet-induced obesity, the latter due to defective diet-induced thermogenesis. Leptin's ability to stimulate thermogenesis, but not to reduce feeding, is markedly attenuated. Acute, selective activation of arcuate GABAergic RIP-Cre neurons, which monosynaptically innervate PVH neurons projecting to the NTS, rapidly stimulates brown fat and increases energy expenditure but does not affect feeding. Importantly, this response is dependent upon GABA release from RIP-Cre neurons. Thus, GABAergic RIP-Cre neurons in the arcuate selectively drive energy expenditure, contribute to leptin's stimulatory effect on thermogenesis, and protect against diet-induced obesity.
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http://dx.doi.org/10.1016/j.cell.2012.09.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3500616PMC
October 2012

Impaired respiratory and body temperature control upon acute serotonergic neuron inhibition.

Science 2011 Jul;333(6042):637-42

Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.

Physiological homeostasis is essential for organism survival. Highly responsive neuronal networks are involved, but their constituent neurons are just beginning to be resolved. To query brain serotonergic neurons in homeostasis, we used a neuronal silencing tool, mouse RC::FPDi (based on the synthetic G protein-coupled receptor Di), designed for cell type-specific, ligand-inducible, and reversible suppression of action potential firing. In mice harboring Di-expressing serotonergic neurons, administration of the ligand clozapine-N-oxide (CNO) by systemic injection attenuated the chemoreflex that normally increases respiration in response to tissue carbon dioxide (CO(2)) elevation and acidosis. At the cellular level, CNO suppressed firing rate increases evoked by CO(2) acidosis. Body thermoregulation at room temperature was also disrupted after CNO triggering of Di; core temperatures plummeted, then recovered. This work establishes that serotonergic neurons regulate life-sustaining respiratory and thermoregulatory networks, and demonstrates a noninvasive tool for mapping neuron function.
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http://dx.doi.org/10.1126/science.1205295DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3729433PMC
July 2011

Mapping cell fate and function using recombinase-based intersectional strategies.

Methods Enzymol 2010 ;477:183-213

Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA.

Cell types are typically defined by expression of a unique combination of genes, rather than a single gene. Intersectional methods therefore become crucial to selectively access these cells for higher resolution fate mapping and functional manipulations. Here, we discuss one such intersectional method. Two recombinase systems (Cre/loxP and Flp/FRT) work together to remove a double STOP cassette and thereby activate expression of a target transgene solely in cells defined by a particular pairwise combination of driver genes. Depending on the nature of the target transgene, this strategy can be used to deliver cell-lineage tracers, sensors, and/or effector molecules to highly selective cell types in vivo. In this chapter, we discuss concepts, reagents, and methods underlying this intersectional approach and encourage consideration of various intersectional and binary methods for accessing uniquely defined cell subsets in the mouse.
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http://dx.doi.org/10.1016/S0076-6879(10)77011-7DOI Listing
December 2010

Rautenlippe Redux -- toward a unified view of the precerebellar rhombic lip.

Curr Opin Cell Biol 2009 Dec 31;21(6):741-7. Epub 2009 Oct 31.

Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.

The rhombic lip (aka rautenlippe) is a germinative neuroepithelium rimming the opening of the hindbrain fourth ventricle during development. Studies spanning more than a century have shown that the rhombic lip produces numerous brainstem neuronal populations unique in their development and functions. While these studies have largely been anatomical in nature, recent applications of newer techniques such as genetic fate mapping and conditional mutagenesis have resolved the rhombic lip into numerous molecularly distinct progenitor domains along spatial and temporal axes that give rise to specific neuron subtypes and systems. This exciting convergence between anatomical and molecular definitions of the rhombic lip and its constituent progenitor populations provides now an important framework for further studies into the genetic basis of development and function of numerous hindbrain neuron types crucial to life.
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http://dx.doi.org/10.1016/j.ceb.2009.10.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3729404PMC
December 2009

An examination of the Chiropteran HoxD locus from an evolutionary perspective.

Evol Dev 2008 Nov-Dec;10(6):657-70

Department of Human Genetics, University of Utah, 15 North 2030 East rm. 5440, Salt Lake City, UT 84112-5331, USA.

Duplications of Hox gene clusters have been suggested as a mechanism whereby new Hox functions can be developed while preserving critical ancestral roles. However, in tetrapods, particularly in mammals, there is great variability in limb structure morphologies that are known to be affected by Hox genes without further Hox cluster duplications. The lack of further duplications suggests that if Hox genes have played a direct role in the morphological elaboration of tetrapod limbs, the changes must have come about from Hox protein sequence changes or from changes regarding the amount, time, and place of Hox gene expression. To investigate whether such changes to Hox genes could play a role in limb elaboration, we examined the HoxD locus in bats, which have both highly elaborated fore- and hindlimbs. We found that while the Chiropteran HoxD13 protein was highly conserved, there was an expansion of HoxD13 expression in the posterior portion of the Chiropteran forelimb and into the leading edge of the wing membrane. We were also able to uncover a number of unique lineage-specific sequence changes to a known HoxD limb enhancer, the Global Control Region (GCR). Further, mouse transgenic assays showed that the Chiropteran GCR has new limb enhancer activity domains beyond that reported for the Human GCR. These results suggest that modulation of Hox gene expression may be a mechanism for effecting morphological change in lineage-specific manner while maintaining ancestral constraints and cluster integrity.
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http://dx.doi.org/10.1111/j.1525-142X.2008.00279.xDOI Listing
January 2009

Large-scale mapping of mutations affecting zebrafish development.

BMC Genomics 2007 Jan 9;8:11. Epub 2007 Jan 9.

Department 3--Genetics, Max-Planck-Institut für Entwicklungsbiologie, Spemannstr, 35/III, 72076 Tübingen, Germany.

Background: Large-scale mutagenesis screens in the zebrafish employing the mutagen ENU have isolated several hundred mutant loci that represent putative developmental control genes. In order to realize the potential of such screens, systematic genetic mapping of the mutations is necessary. Here we report on a large-scale effort to map the mutations generated in mutagenesis screening at the Max Planck Institute for Developmental Biology by genome scanning with microsatellite markers.

Results: We have selected a set of microsatellite markers and developed methods and scoring criteria suitable for efficient, high-throughput genome scanning. We have used these methods to successfully obtain a rough map position for 319 mutant loci from the Tübingen I mutagenesis screen and subsequent screening of the mutant collection. For 277 of these the corresponding gene is not yet identified. Mapping was successful for 80 % of the tested loci. By comparing 21 mutation and gene positions of cloned mutations we have validated the correctness of our linkage group assignments and estimated the standard error of our map positions to be approximately 6 cM.

Conclusion: By obtaining rough map positions for over 300 zebrafish loci with developmental phenotypes, we have generated a dataset that will be useful not only for cloning of the affected genes, but also to suggest allelism of mutations with similar phenotypes that will be identified in future screens. Furthermore this work validates the usefulness of our methodology for rapid, systematic and inexpensive microsatellite mapping of zebrafish mutations.
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http://dx.doi.org/10.1186/1471-2164-8-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1781435PMC
January 2007
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