Biology subjects

Dale, N.

Publications and source records attributed to Dale, N..

18 recordsLinked to original sources

bioRxiv2026

A discrete Connexin26+ neural crest lineage emerges in mid-life and mediates enhanced central brainstem responses to elevated CO2 levels for deep breathing.

The precise control of breathing is fundamental to vertebrate survival. Increased PCO2 in blood and brain parenchyma causes an increase in both the frequency and volume of lung ventilation. We have previously demonstrated that CO2 directly binds to connexin26 (Cx26) hemichannels causing them to open and allow release ATP. We now document the role of Cx26 as a direct physiological CO2 sensor in vivo. Here we describe a unique Cx26+ neural crest cell lineage that populates the ventral brainstem in the vicinity of the PreBoetz nucleus/caudal CO2 chemosensory area during middle age and dies again in old age. Ablating Cx26 genetically specifically within this population of about 20 cells by two independent neural crest Cre-driver lines leads to a loss of local ATP release in the posterior chemosensory area as well as a 40% reduction in elevated tidal volume responses specifically in middle age, as measured by whole-body plethysmography. These in vivo effects change over a life-time: they directly mirror the arrival, wiring in middle age and later death of this cell population in old age. This is a first known example of a middle age change in cranial neural crest lineage composition and highlights the significant power of very few cells for global metabolism. Such lineage-dependent middle-age dynamics also impacts upon the evolution of eusociality: altricial naked pups of our common amniote/synapsid ancestors were heated by by the breath of their (middle-aged) carers, sensing elevated CO2 levels in hypercapnic burrows. Such mechanistic exaptation enabled small amniotes to sense and survive the lethal global CO2 spikes during the Permo-Triassic and other extinction events.

neuroscience↗

bioRxiv2026

The essential molecular components for cellular CO2 sensing via connexins

CO2 opens a subset of connexin hemichannels by binding to a site in the cytoplasmic domain of the channel. From outside the cell, CO2 must cross at least one membrane to reach this site. We have used Neuro-2A cells, which exhibit very low expression of CO2 permeable aquaporins (AQPs) and do not express any of the connexins (Cxs) known to be CO2 sensitive, to evaluate the minimal complement of molecular components required to recapitulate whole cell CO2 sensitivity mediated by connexins (assayed by either whole cell patch clamp recordings or real time recordings of ATP release via a co-expressed genetically encoded ATP sensor). Neuro-2A cells that expressed either Cx26, Cx32 or Cx43 on their own did not exhibit CO2-dependent connexin hemichannel gating. Expression of AQP1 or AQP5 either with or without carbonic anhydrase 2 (CA2) did not reveal any endogenous CO2 sensitivity of Neuro-2A cells. Only by expressing one of Cx26, Cx32 or Cx43 with either AQP1 or AQP5, plus CA2 were we able to reconstitute whole cell CO2 sensitivity. We found that expression of Cx26 with either AQP1 or AQP5 resulted in high levels of cell death. This was prevented by co-expression of CA2. Simulations of the influx and diffusion of CO2 show that CA2 prevents accumulation of intracellular CO2 and excessive activation of Cx26, thus protecting the cells from death. Surveying the transcriptome of cells that express CO2 sensitive connexins shows that many also express CO2 permeable aquaporins and CA2. We suggest that connexins, aquaporins and carbonic anhydrases represent the minimal trifecta of components required for cellular CO2 sensing.

cell biology↗

bioRxiv2026

Deep evolutionary origins of the connexin gene family

The vertebrate connexin family encodes a diverse repertoire of transmembrane channels that mediate both intercellular communication and cytosol to extracellular space exchange. Their apparent absence in non-chordates has led to the prevailing view that connexins arose during chordate evolution with analogous functions performed in non-chordates by the innexins, a structurally similar but non-homologous protein family. Here, using a combination of sequence and structural analyses, we discover the presence of connexins in anthozoan and protostome genomes despite widespread secondary gene loss in Bilateria. We show that these connexins can be present in up to 100 copies per genome and are often found as N-terminal domains of NOD-like receptors (NLRs) or other immune genes. We show that these invertebrate connexins localise at the cell membrane, function as either hemichannels (anthozoans and protostomes) or gap junctions (protostomes), and respond to depolarisation enabling the transfer of small molecules. Further, we demonstrate that a subset of the invertebrate connexin-like domains are sensitive to CO2 and mirroring findings in vertebrate connexins, the CO2-mediated gating stems from the formation of a carbamate bridge between neighbouring subunits. Taken together, we trace the evolution of this gene family to the cnidarian-bilaterian ancestor, demonstrate functional similarity between invertebrate and vertebrate connexins, and suggest an ancient role of connexins in innate immunity.

evolutionary biology↗

bioRxiv2026

Structure of Connexin26 from Lepidosiren paradoxa

Connexin gap junction channels enable the direct exchange of molecules and ions between cells. Channel opening is regulated by various physiological stimuli. Human connexin26 gap junction channels close in response to elevated levels of CO2 in a process that is independent of pH, with structures demonstrating a [CO2]-dependent conformational change. Cx26 from the lungfish, Lepidosiren paradoxa is also CO2 sensitive. Here we solve its structure at high [CO2]. We observe an open conformation of the protein where the N-terminal helix that influences the aperture of the pore is pulled away from the centre. This conformation is stabilised by the presence of a detergent binding between TM3 and TM4 that would prevent the conformational changes necessary to close the protein upon exchange to high [CO2]. The structure supports a mechanism in which the conformation of a motif shown to be important for CO2 sensitivity is correlated with the opening of the pore.

biochemistry↗

bioRxiv2026

Genome writing and Targeted Delivery of the NKX6-3/ANK1 gene cluster and its Type 2 Diabetes GWAS Variants to Human iPSCs

Genome-wide association studies (GWAS) identified over 600 loci containing single-nucleotide polymorphisms (SNPs) associated with type 2 diabetes (T2D), most of which reside in non-coding regions. Among the set of T2D SNPs, linking causal genome variants to disease risk experimentally has remained a challenge; however, advances in synthetic mammalian genome writing techniques now enable the delivery of multiple haplotypes to human induced pluripotent stem cells (hiPSCs) to create a series of isogenic cell lines that can be differentiated and phenotyped in vitro. Here, to begin efforts in dissecting a T2D GWAS locus, we engineered an NKX6-3/ANK1 gene cluster knockout hiPSC line and introduced a landing pad facilitating the delivery of synthetic haplotype payloads. We built four haplotypes, including several that are not observed in nature, containing risk SNPs spanning the NKX6-3/ANK1 gene cluster using a method called "variant Switching Auxotrophic markers for Integration" (vSwAP-In), and integrated them precisely into hiPSCs. NKX6-3/ANK1 deletion blocked pancreatic progenitor and skeletal muscle differentiation, suggesting that NKX6-3 and ANK1 are required for early pancreatic and skeletal muscle development, and perhaps related to the existence of two nonoverlapping sets of SNPs in linkage disequilibrium that associate with the expression of the two adjacent genes. When NKX6-3/ANK1 T2D "Risk" haplotypes were reintroduced, skeletal muscle and pancreatic progenitor differentiation capabilities were restored. ANK1 expression was elevated in the ANK1 Risk and All-Risk haplotypes compared to the NKX6-3 Risk and Non-Risk haplotypes, establishing a functional experimental platform to examine risk SNP clusters in their native contexts. Overall, this work establishes a platform for the dissection of GWAS loci using synthetic haplotype genomics in hiPSCs. Significance StatementGenome-wide association studies have been used to identify disease-associated SNPs; however, most SNPs lie in non-coding regions, making functional experimentation difficult to perform. Using vSwAP-In, a yeast-based DNA variant-building method, and mSwAP-In, a mammalian genome engineering approach, we establish a platform for functional GWAS dissection in hiPSCs. This platform allows us to build DNA harboring virtually any combination of disease-risk SNPs, allowing for functional characterization of SNPs without the limitations of linkage disequilibrium. We demonstrate this approach using a Type 2 diabetes GWAS gene cluster, NKX6-3/ANK1.

genetics↗

bioRxiv2025

Genetics of growth rate in induced pluripotent stem cells

Human induced pluripotent stem cells (iPSCs) have transformed biomedical research by enabling the generation of diverse cell types from accessible somatic tissues. However, certain fundamental biological properties, such as the genetic and epigenetic determinants of iPSC proliferation, remain poorly characterized. We measured the growth of iPSC lines derived from 602 unique donors using high-throughput time-lapse imaging, quantified proliferation through a growth Area-Under-the-Curve (gAUC) phenotype, and correlated gAUC with the gene expression and genotype of the cell lines. We identified 3,091 genes associated with gAUC, many of which are well established regulators of cell proliferation. We also found that rare deleterious variants in WDR54 were associated with reduced iPSC growth and that WDR54 was differentially expressed with respect to gAUC. Although no common variants showed a genome-wide association with gAUC, iPSC lines from monozygotic twins were highly correlated, and common genetic variation explained approximately 71-75% of the variance in iPSC growth rates. These results indicate a complex genetic architecture of iPSC growth rates, where rare, large-effect variants in important growth regulators, including WDR54, are layered onto a highly polygenic background. These findings have important implications for the design of pooled iPSC-based studies and disease models, which may be confounded by intrinsic growth differences.

developmental biology↗

bioRxiv2025

CO2 sensitive connexin channel synapses in the VTA release 5HT to regulate dopaminergic neurons

Hypercapnic arousal is a life-preserving reflex that promotes awakening in response to elevated PCO2, yet the cellular mechanisms by which CO2 is detected remain incompletely understood. Serotonergic neurons of the dorsal raphe (DR) have been implicated in hypercapnic responses, but the molecular sensor that directly detects CO2 within this circuit is unknown. Here, we show that the CO2-gated connexin 26 (Cx26) hemichannel is expressed on serotonergic terminals projecting from the DR to the ventral tegmental area (VTA). Brief elevations in PCO2 modulated the excitability of VTA dopamine neurons through serotonergic signaling without altering glutamatergic transmission, and these effects were abolished by pharmacological inhibition of hemichannels. By expressing Cx26 and genetically encoded GRAB5HT sensors in cultured cells, we further demonstrate that Cx26 hemichannels opened by elevated PCO2 are directly permeable to serotonin. Selective removal of CO2 sensitivity from Cx26 in DR serotonergic neurons delayed arousal from sleep during transient hypercapnia and reduced activation of VTA dopamine neurons in vivo. Together, these findings identify Cx26 hemichannels as a direct CO2 sensor that enables serotonin release through a channel co-synapse and contributes to hypercapnic arousal.

neuroscience↗

bioRxiv2025

Cell-to-cell signalling mediated via CO2: activity dependent CO2 production in the axonal node opens Cx32 in the Schwann cell paranode.

Loss of function mutations of Cx32, which is expressed in Schwann cells, cause X-linked Charcot Marie Tooth disease, a slowly progressive peripheral neuropathy. Cx32 is thus essential for the maintenance of myelin. During action potential propagation, Cx32 hemichannels in the Schwann cell paranode are thought to open and release ATP. As Cx32 hemichannels are directly sensitive to CO2, we have tested whether CO2 produced in the axon, as a consequence of the energetic demands of action potential propagation, might gate Cx32 hemichannels. Using isolated sciatic nerve from the mouse, we have shown that the critical components required for intercellular CO2 signalling are present (nodal mitochondria, the source of CO2; a CO2-permeable aquaporin, AQP1; paranodal Cx32; and carbonic anhydrase). We have used a membrane impermeant fluorescent dye FITC, which can permeate Cx32 hemichannels, to demonstrate the opening of Cx32 in Schwann cells in response to an external CO2 stimulus or during action potential propagation in the isolated nerve. Pharmacological blockade of AQP1 or allosteric enhancement of carbonic anhydrase activity greatly reduced Cx32 gating during action potential firing. By contrast, inhibition of carbonic anhydrase with acetazolamide greatly increased Cx32 gating. Cx32 gating was unabected by the G-protein blocker GDP{beta}S, indicating that it was not mediated by G protein coupled receptors. By expressing a modified Cx32 subunit, Cx32DN, that coassembles with Cx32WT, we have shown that the activity dependent dye loading of Schwann cells depends upon CO2 binding to Cx32. This CO2-dependent opening of Cx32 also mediates an activity dependent Ca2+ influx into the paranode and, by increasing the leak current across the myelin sheath, slows the conduction velocity. Our data demonstrate that CO2 can act via connexins to mediate neuron-to-glia signalling and that CO2 permeable aquaporins and carbonic anhydrase are key components of this signalling mechanism.

neuroscience↗

bioRxiv2025

On the mechanisms of permselectivity of connexin hemichannels to small molecules

Connexins can either that act as hemichannels, to facilitate ion and small molecule movement from the cytosol to the extracellular space or as gap junction channels to provide a pathway for solute exchange between cells. Connexins are ubiquitously expressed throughout the body and are implicated in a wide range of processes. The permselectivity of connexin hemichannels for small neurochemicals remains poorly understood. By coexpressing genetically encoded fluorescent sensors for ATP, glutamate and lactate with a range of connexins, we examined the ability of different hemichannels to permit release of these compounds under physiological conditions and in response to physiological stimuli (small changes in PCO2 and transmembrane depolarisation). We found that some connexin hemichannels were relatively non-selective (Cx26, Cx32, Cx43, Cx31.1) allowing passage of ATP, glutamate and lactate. By contrast other connexin hemichannels (Cx36, Cx46 and Cx50) were highly selective. Cx36 and Cx46 hemichannels allowed release of ATP, but not glutamate or lactate. The size of the permeating molecule cannot be the sole determinant of permselectivity. By contrast, Cx50 hemichannels permitted the release of lactate and glutamate but not ATP. We also found that the nature of the opening stimulus could alter the permselectivity of the hemichannel-for some of the relatively non-selective connexins, hemichannel opening via depolarisation was ineffective at allowing release of lactate. By performing a mutational analysis, informed by the differential selectivity of the closely related Cx46 and Cx50 hemichannels, we found that the charge on the N-terminus and N-terminus-TM2 interactions are key contributors to permselectivity for ATP.

cell biology↗

bioRxiv2025

Connexin50 hemichannels are opened by CO2: implications for lens physiology

Connexin50 (Cx50) is expressed in lens fibre cells. As mutations of Cx50 cause cataracts its physiological role in the lens must be important. We have used recent cryoEM structures of Cx50 and the predictive power of Alphafold3 to identify the presence of a carbamylation motif, originally described in Cx26, that suggests that Cx50 might be CO2 sensitive. By expressing the naturally truncated version of Cx50 in HeLa cells and utilising coexpression of genetically encoded sensors iGluSnFr or eLACCO1.1, we have demonstrated the CO2-dependent opening of Cx50 hemichannels, and their permeability to lactate and glutamate. By mutating the two key residues of the carbamylation motif, K105 and K140, we have shown that the motif is required for CO2 sensitivity. Mutations of the residue V44 cause cataracts and these mutations abolish the CO2 sensitivity of Cx50. Using Fluo-4 Ca2+ imaging with lens slices we have demonstrated CO2-dependent Ca2+ influxes into fibre cells that are blocked by La3+ and exhibit the same CO2 dose dependence as Cx50 hemichannels. Lens fibre cells respond to glutamate via NMDA receptors and our data shows that the Ca2+ influx to raised PCO2 partially depends on NMDA receptor activation. We hypothesize that CO2-dependent gating of Cx50, subsequent release of glutamate resulting in the downstream activation of glutamate receptors, and the consequent alterations in transmembrane Na+ fluxes, provide homeostatic control of the microcirculation system that is critical for lens health.

cell biology↗

bioRxiv2025

CO2-dependent opening of Connexin 43 hemichannels

Sequence and structure comparisons between alpha and beta connexins, Cx43 and Cx26, revealed that Cx43 has a motif, the carbamylation motif, that confers CO2-sensitivity on a subset of beta connexins. By using a fluorescent dye loading assay, whole cell patch clamp recordings and real time measurement of ATP release via GRABATP we have demonstrated that Cx43 hemichannels open in a highly CO2 sensitive manner over the range 20 to 70 mmHg. Mutational analysis confirms that the equivalent residues to those in Cx26 that have been shown to be involved in mediating the effects of CO2 on gating of hemichannels and gap junction channels, also mediate Cx43 hemichannel gating. Our data predicts that Cx43 will be partially open and able to release ATP at resting physiological levels of PCO2. We have tested this prediction in acute hippocampal slices, by showing that CO2-dependent enhancement of synaptic transmission can be blocked by the Cx43-selective mimetic peptide Gap26. Our data resolves an inconsistency in the literature between in vivo studies suggesting that Cx43 hemichannels are at least partially open at rest, and in vitro studies, performed in the absence of HCO3-/CO2 buffering that show Cx43 hemichannels are shut. Our evidence suggests that the ancestral gene that duplicated to give the alpha and beta connexin clades must have possessed the carbamylation motif. CO2 sensitivity is thus a fundamental ancient characteristic of several connexins that has been lost in more recently derived members of this gene family.

neuroscience↗

bioRxiv2023

Structures of wild-type and a constitutively closed mutant of connexin26 shed light on channel regulation by CO2

Connexins allow intercellular communication by forming gap junction channels (GJCs) between juxtaposed cells. Connexin26 (Cx26) can be regulated directly by CO2. This is proposed to be mediated through carbamylation of K125. We show that mutating K125 to glutamate, mimicking the negative charge of carbamylation, causes Cx26 GJCs to be constitutively closed. Through cryo-EM we observe that the K125E mutation pushes a conformational equilibrium towards the channel having a constricted pore entrance, similar to effects seen on raising the partial pressure of CO2. In previous structures of connexins, the cytoplasmic loop, important in regulation and where K125 is located, is disordered. Through further cryo-EM studies we trap distinct states of Cx26 and observe density for the cytoplasmic loop. The interplay between the position of this loop, the conformations of the transmembrane helices and the position of the N-terminal helix, which controls the aperture to the pore, provides a mechanism for regulation.

biochemistry↗

bioRxiv2022

Neural correlate of reduced respiratory chemosensitivity during chronic epilepsy

Central autonomic cardiorespiratory dysfunction underlies sudden unexpected death in epilepsy (SUDEP). Here we used single cell neuronal Ca2+ imaging and intrahippocampal kainic acid (KA)-induced chronic epilepsy in mice to investigate progressive changes in key cardiorespiratory brainstem circuits during chronic epilepsy. Following induction of status epilepticus (SE), adaptive ventilatory responses to hypercapnia were reduced in mice with chronic epilepsy for 5 weeks post-SE with partial recovery at week 7. These changes were paralleled by post-SE alterations in the chemosensory responses of neurons in the retrotrapezoid nucleus (RTN). Neurons that displayed adapting responses to hypercapnia were less prevalent and exhibited smaller responses over weeks 3-5, whereas neurons that displayed graded responses to hypercapnia became more prevalent by week 7. Over the same period, chemosensory responses of the presympathetic rostral ventrolateral medullary neurons showed no change. Mice with chronic epilepsy showed enhanced sensitivity to seizures, which can invade the RTN and possibly impair further the chemosensory circuits. Our work suggests that assessment of respiratory chemosensitivity may have potential for identifying people at risk of SUDEP.

neuroscience↗

bioRxiv2021

CXCL17 is an endogenous inhibitor of CXCR4 via a novel mechanism of action

CXCL17 is the most recently described chemokine. It is principally expressed by mucosal tissues, where it facilitates chemotaxis of monocytes, dendritic cells, and macrophages and has antimicrobial properties. CXCL17 is also implicated in the pathology of inflammatory disorders and progression of several cancers, as well as being highly upregulated during viral infections of the lung. However, the exact role of CXCL17 in health and disease is largely unknown, mainly due to a lack of known molecular targets mediating CXCL17 functional responses. Using a range of bioluminescence resonance energy transfer (BRET) based assays, here we demonstrate that CXCL17 inhibits CXCR4-mediated signalling and ligand binding. Moreover, CXCL17 interacts with neuropillin-1, a VEGFR2 co-receptor. Additionally, we find CXCL17 only inhibits CXCR4 ligand binding in intact cells and demonstrate that this effect is mimicked by known glycosaminoglycan binders, surfen and protamine sulfate. This indicates that CXCL17 inhibits CXCR4 by a unique mechanism of action that potentially requires the presence of a glycosaminoglycan containing accessory protein. Altogether, our results reveal that CXCL17 is an endogenous inhibitor of CXCR4 and represents an important discovery in our understanding of the (patho) physiological functions of CXCL17 and regulation of CXCR4 signalling.

pharmacology and toxicology↗

bioRxiv2020

Conformational changes and channel gating induced by CO2 binding to Connexin26

CO2 is the inevitable by-product of oxidative metabolism. Many physiological processes such as breathing1 and cerebral blood flow2 are sensitive to CO2. Historically, the physiological actions of CO2 have been regarded as being mediated exclusively via changes in pH. Here, we change this consensus by showing that the gap junction protein Connexin26 (Cx26) acts as a receptor for CO2 showing sensitivity to modest changes in PCO2 around the physiological norm3-6. Mass spectrometry analysis7 shows that CO2 carbamylates specific lysines on a regulatory loop of Cx26 at high, but not at low levels of PCO2. By means of high resolution cryo-EM, we have solved structures of Cx26 gap junctions at 1.9, 2.2 and 2.1 [A] for PCO2 of 90, 55 and 20 mmHg respectively, all at pH 7.4. Classification of the particles at each level of PCO2, shows the transmembrane helices and N-terminal helix flexing at the dynamic cytoplasmic side of the protein. Gating of Cx26 gap junctions by CO2 involves movements of the N-terminus to plug the channel at high PCO2. We therefore provide mechanistic detail for a new paradigm by which CO2 can directly control breathing8 and other key physiological functions9.

biochemistry↗

bioRxiv2020

Connexin26 mediates CO2-dependent regulation of breathing via glial cells of the medulla oblongata

Breathing is highly sensitive to the PCO2 of arterial blood. Although CO2 is detected via the proxy of pH, CO2 acting directly via Cx26 may also contribute to the regulation of breathing. Here we exploit our knowledge of the structural motif of CO2-binding to Cx26 to devise a dominant negative subunit (Cx26DN) that removes the CO2-sensitivity from endogenously expressed wild type Cx26. Expression of Cx26DN in glial cells of a circumscribed region of the medulla - the caudal parapyramidal area - reduced the adaptive change in tidal volume and minute ventilation by approximately 30% at 6% inspired CO2. As central chemosensors mediate about 70% of the total response to hypercapnia, CO2-sensing via Cx26 in the caudal parapyramidal area contributed about 45% of the centrally-mediated ventilatory response to CO2. Our data unequivocally links the direct sensing of CO2 to the chemosensory control of breathing and demonstrates that CO2-binding to Cx26 is a key transduction step in this fundamental process.

neuroscience↗

bioRxiv2019

Opposing modulation of Cx26 gap junctions and hemichannels by CO2

Cx26 hemichannels open in response to moderate elevations of CO2 (PCO2 55 mmHg) via a carbamylation reaction that depends on residues K125 and R104. Here we investigate the action of CO2 on Cx26 gap junctions. Using a dye transfer assay, we found that an elevated PCO2 of 55 mmHg greatly delayed the permeation of a fluorescent glucose analogue (NBDG) between HeLa cells coupled by Cx26 gap junctions. However, the mutations K125R or R104A abolished this effect of CO2. Whole cell recordings demonstrated that elevated CO2 reduced the Cx26 gap junction conductance (median reduction 5.6 nS, 95% confidence interval, 3.2 to 11.9 nS) but had no effect on Cx26K125R or Cx31 gap junctions. CO2 can cause intracellular acidification, but using 30 mM propionate we found that acidification in the absence of a change in PCO2 caused a median reduction in the gap junction conductance of 5.3 nS (2.8 to 8.3 nS). This effect of propionate was unaffected by the K125R mutation (median reduction 7.7 nS, 4.1 to 11.0 nS). pH-dependent and CO2-dependent closure of the gap junction are thus mechanistically independent. Mutations of Cx26 associated with the Keratitis Ichthyosis Deafness syndrome (N14K, A40V and A88V) also abolished the CO2-dependent gap junction closure. Elastic network modelling suggests that the lowest entropy state when CO2 is bound, is the closed configuration for the gap junction but the open state for the hemichannel. The opposing actions of CO2 on Cx26 gap junctions and hemichannels thus depend on the same residues and presumed carbamylation reaction.

cell biology↗

bioRxiv2018

Analyzing the brainstem circuits for respiratory chemosensitivity in freely moving mice

The regulated excretion of CO2 during breathing is a key life-preserving homeostatic mechanism. In the rostral medulla oblongata, neurons in two nuclei -the retrotrapezoid nucleus (RTN) and the rostral medullary Raphe -have been proposed as central CO2 chemosensors that mediate adaptive changes in breathing. One such adaptive change is active expiration, thought to be controlled by the lateral parafacial region (pFL). Here we use promoter-driven expression of GCaMP6 and head-mounted mini-microscopes to image the Ca2+ activity in neurons and glia of RTN, Raphe and pFL in awake adult mice during inspiration of elevated CO2 to discriminate their roles in the adaptive response to hypercapnia. While there were multiple types of neuronal response to hypercapnia in both the RTN and the Raphe, a substantial proportion of neurons in the Raphe encoded the inspired level of CO2. By contrast, such responses were very rare in the RTN and the responses of RTN neurons suggest that this nucleus plays an integrative rather than a direct sensing role in the chemosensory reflex. pFL neurons were reliably activated by hypercapnia and their activity preceded active expiration suggesting a key causal link to this aspect of breathing. Our analysis considerably revises understanding of chemosensory control in the adult awake mouse and paves the way to understanding how breathing is coordinated with complex non-ventilatory behaviours such as swallowing and vocalisation.

neuroscience↗