Mapping the face in the somatosensory brainstem

Sensorimotor regulation of facial expression - An untouched frontier

Facial expression is a critical form of nonverbal social communication which promotes emotional exchange and affiliation among humans. Facial expressions are generated via precise contraction of the facial muscles, guided by sensory feedback. While the neural pathways underlying facial motor control are well characterized in humans and primates, it remains unknown how tactile and proprioceptive information reaches these pathways to guide facial muscle contraction. Thus, despite the importance of facial expressions for social functioning, little is known about how they are generated as a unique sensorimotor behavior. In this review, we highlight current knowledge about sensory feedback from the face and how it is distinct from other body regions. We describe connectivity between the facial sensory and motor brain systems, and call attention to the other brain systems which influence facial expression behavior, including vision, gustation, emotion, and interoception. Finally, we petition for more research on the sensory basis of facial expressions, asserting that incomplete understanding of sensorimotor mechanisms is a barrier to addressing atypical facial expressivity in clinical populations.

Bilateral Whisker Representations in the Primary Somatosensory Cortex in Robo3cKO Mice Are Reflected in the Primary Motor Cortex

In Robo3cKO mice, midline crossing defects of the trigeminothalamic projections from the trigeminal principal sensory nucleus result in bilateral whisker maps in the somatosensory thalamus and consequently in the face representation area of the primary somatosensory (S1) cortex (Renier et al., 2017; Tsytsarev et al., 2017). We investigated whether this bilateral sensory representation in the whisker-barrel cortex is also reflected in the downstream projections from the S1 to the primary motor (M1) cortex. To label these projections, we injected anterograde viral axonal tracer in S1 cortex. Corticocortical projections from the S1 distribute to similar areas across the ipsilateral hemisphere in control and Robo3cKO mice. Namely, in both genotypes they extend to the M1, premotor/prefrontal cortex (PMPF), secondary somatosensory (S2) cortex. Next, we performed voltage-sensitive dye imaging (VSDi) in the left hemisphere following ipsilateral and contralateral single whisker stimulation. While controls showed only activation in the contralateral whisker barrel cortex and M1 cortex, the Robo3cKO mouse left hemisphere was activated bilaterally in both the barrel cortex and the M1 cortex. We conclude that the midline crossing defect of the trigeminothalamic projections leads to bilateral whisker representations not only in the thalamus and the S1 cortex but also downstream from the S1, in the M1 cortex.

Callosal inputs generate side-invariant receptive fields in the barrel cortex

Barrel cortex integrates contra- and ipsilateral whiskers' inputs. While contralateral inputs depend on the thalamocortical innervation, ipsilateral ones are thought to rely on callosal axons. These are more abundant in the barrel cortex region bordering with S2 and containing the row A-whiskers representation, the row lying nearest to the facial midline. Here, we ask what role this callosal axonal arrangement plays in ipsilateral tactile signaling. We found that novel object exploration with ipsilateral whiskers confines c-Fos expression within the highly callosal subregion. Targeting this area with in vivo patch-clamp recordings revealed neurons with uniquely strong ipsilateral responses dependent on the corpus callosum, as assessed by tetrodotoxin silencing and by optogenetic activation of the contralateral hemisphere. Still, in this area, stimulation of contra- or ipsilateral row A-whiskers evoked an indistinguishable response in some neurons, mostly located in layers 5/6, indicating their involvement in the midline representation of the whiskers' sensory space.

Functional and structural synaptic remodeling mechanisms underlying somatotopic organization and reorganization in the thalamus

The somatosensory system organizes the topographic representation of body maps, termed somatotopy, at all levels of an ascending hierarchy. Postnatal maturation of somatotopy establishes optimal somatosensation, whereas deafferentation in adults reorganizes somatotopy, which underlies pathological somatosensation, such as phantom pain and complex regional pain syndrome. Here, we focus on the mouse whisker somatosensory thalamus to study how sensory experience shapes the fine topography of afferent connectivity during the critical period and what mechanisms remodel it and drive a large-scale somatotopic reorganization after peripheral nerve injury. We will review our findings that, following peripheral nerve injury in adults, lemniscal afferent synapses onto thalamic neurons are remodeled back to immature configuration, as if the critical period reopens. The remodeling process is initiated with local activation of microglia in the brainstem somatosensory nucleus downstream to injured nerves and heterosynaptically controlled by input from GABAergic and cortical neurons to thalamic neurons. These fruits of thalamic studies complement well-studied cortical mechanisms of somatotopic organization and reorganization and unveil potential intervention points in treating pathological somatosensation.

Neuronal birthdate reveals topography in a vestibular brainstem circuit for gaze stabilization

Across the nervous system, neurons with similar attributes are topographically organized. This topography reflects developmental pressures. Oddly, vestibular (balance) nuclei are thought to be disorganized. By measuring activity in birthdated neurons, we revealed a functional map within the central vestibular projection nucleus that stabilizes gaze in the larval zebrafish. We first discovered that both somatic position and stimulus selectivity follow projection neuron birthdate. Next, with electron microscopy and loss-of-function assays, we found that patterns of peripheral innervation to projection neurons were similarly organized by birthdate. Finally, birthdate revealed spatial patterns of axonal arborization and synapse formation to projection neuron outputs. Collectively, we find that development reveals previously hidden organization to the input, processing, and output layers of a highly conserved vertebrate sensorimotor circuit. The spatial and temporal attributes we uncover constrain the developmental mechanisms that may specify the fate, function, and organization of vestibulo-ocular reflex neurons. More broadly, our data suggest that, like invertebrates, temporal mechanisms may assemble vertebrate sensorimotor architecture.

Human stem cell models to study placode development, function and pathology

Placodes are embryonic structures originating from the rostral ectoderm that give rise to highly diverse organs and tissues, comprising the anterior pituitary gland, paired sense organs and cranial sensory ganglia. Their development, including the underlying gene regulatory networks and signalling pathways, have been for the most part characterised in animal models. In this Review, we describe how placode development can be recapitulated by the differentiation of human pluripotent stem cells towards placode progenitors and their derivatives, highlighting the value of this highly scalable platform as an optimal in vitro tool to study the development of human placodes, and identify human-specific mechanisms in their development, function and pathology.

Neurosensory development of the four brainstem-projecting sensory systems and their integration in the telencephalon

Somatosensory, taste, vestibular, and auditory information is first processed in the brainstem. From the brainstem, the respective information is relayed to specific regions within the cortex, where these inputs are further processed and integrated with other sensory systems to provide a comprehensive sensory experience. We provide the organization, genetics, and various neuronal connections of four sensory systems: trigeminal, taste, vestibular, and auditory systems. The development of trigeminal fibers is comparable to many sensory systems, for they project mostly contralaterally from the brainstem or spinal cord to the telencephalon. Taste bud information is primarily projected ipsilaterally through the thalamus to reach the insula. The vestibular fibers develop bilateral connections that eventually reach multiple areas of the cortex to provide a complex map. The auditory fibers project in a tonotopic contour to the auditory cortex. The spatial and tonotopic organization of trigeminal and auditory neuron projections are distinct from the taste and vestibular systems. The individual sensory projections within the cortex provide multi-sensory integration in the telencephalon that depends on context-dependent tertiary connections to integrate other cortical sensory systems across the four modalities.

Layers 3 and 4 Neurons of the Bilateral Whisker-Barrel Cortex

In Robo3^R3-5cKO mouse brain, rhombomere 3-derived trigeminal principal nucleus (PrV) neurons project bilaterally to the somatosensory thalamus. As a consequence, whisker-specific neural modules (barreloids and barrels) representing whiskers on both sides of the face develop in the sensory thalamus and the primary somatosensory cortex. We examined the morphological complexity of layer 4 barrel cells, their postsynaptic partners in layer 3, and functional specificity of layer 3 pyramidal cells. Layer 4 spiny stellate cells form much smaller barrels and their dendritic fields are more focalized and less complex compared to controls, while layer 3 pyramidal cells did not show notable differences. Using in vivo 2-photon imaging of a genetically encoded fluorescent [Ca²⁺] sensor, we visualized neural activity in the normal and Robo3^R3-5cKO barrel cortex in response to ipsi- and contralateral single whisker stimulation. Layer 3 neurons in control animals responded only to their contralateral whiskers, while in the mutant cortex layer 3 pyramidal neurons showed both ipsi- and contralateral whisker responses. These results indicate that bilateral whisker map inputs stimulate different but neighboring groups of layer 3 neurons which normally relay contralateral whisker-specific information to other cortical areas.

The topography of corticopontine projections is controlled by postmitotic expression of the area-mapping gene Nr2f1

Axonal projections from layer V neurons of distinct neocortical areas are topographically organized into discrete clusters within the pontine nuclei during the establishment of voluntary movements. However, the molecular determinants controlling corticopontine connectivity are insufficiently understood. Here, we show that an intrinsic cortical genetic program driven by Nr2f1 graded expression is directly implicated in the organization of corticopontine topographic mapping. Transgenic mice lacking cortical expression of Nr2f1 and exhibiting areal organization defects were used as model systems to investigate the arrangement of corticopontine projections. By combining three-dimensional digital brain atlas tools, Cre-dependent mouse lines and axonal tracing, we show that Nr2f1 expression in postmitotic neurons spatially and temporally controls somatosensory topographic projections, whereas expression in progenitor cells influences the ratio between corticopontine and corticospinal fibres passing the pontine nuclei. We conclude that cortical gradients of area-patterning genes are directly implicated in the establishment of a topographic somatotopic mapping from the cortex onto pontine nuclei.

Summary: Cortical gradient expression of the area patterning gene Nr2f1 spatially and temporally controls corticopontine topographic connectivity in layer V projection neurons.

Social touch-like tactile stimulation activates a tachykinin 1-oxytocin pathway to promote social interactions

It is well known that affective and pleasant touch promotes individual well-being and facilitates affiliative social communication, although the neural circuit that mediates this process is largely unknown. Here, we show that social-touch-like tactile stimulation (ST) enhances firing of oxytocin neurons in the mouse paraventricular hypothalamus (PVH) and promotes social interactions and positively reinforcing place preference. These results link pleasant somatosensory stimulation to increased social interactions and positive affective valence. We further show that tachykinin 1 (Tac1⁺) neurons in the lateral and ventrolateral periaqueductal gray (l/vlPAG) send monosynaptic excitatory projections to PVH oxytocin neurons. Functionally, activation of PVH-projecting Tac1⁺ neurons increases firing of oxytocin neurons, promotes social interactions, and increases preference for the social touch context, whereas reducing activity of Tac1⁺ neurons abolishes ST-induced oxytocin neuronal firing. Together, these results identify a dipeptidergic pathway from l/vlPAG Tac1⁺ neurons to PVH oxytocin neurons, through which pleasant sensory experience promotes social behavior.

A brain-to-spinal sensorimotor loop for repetitive self-grooming

Self-grooming is a complex behavior with important biological functions and pathological relevance. How the brain coordinates with the spinal cord to generate the repetitive movements of self-grooming remains largely unknown. Here, we report that in the caudal part of the spinal trigeminal nucleus (Sp5C), neurons that express Cerebellin-2 (Cbln2⁺) form a neural circuit to the cervical spinal cord to maintain repetitive orofacial self-grooming. Inactivation of Cbln2⁺ Sp5C neurons blocked both sensory-evoked and stress-induced repetitive orofacial self-grooming. Activation of these neurons triggered short-latency repetitive forelimb movements that resembled orofacial self-grooming. The Cbln2⁺ Sp5C neurons were monosynaptically innervated by both somatosensory neurons in the trigeminal ganglion and paraventricular hypothalamic neurons. Among the divergent projections of Cbln2⁺ Sp5C neurons, a descending pathway that innervated motor neurons and interneurons in the cervical spinal cord was necessary and sufficient for repetitive orofacial self-grooming. These data reveal a brain-to-spinal sensorimotor loop for repetitive self-grooming in mice.

Aberrant early growth of individual trigeminal sensory and motor axons in a series of mouse genetic models of 22q11.2 deletion syndrome

We identified divergent modes of initial axon growth that prefigure disrupted differentiation of the trigeminal nerve (CN V), a cranial nerve essential for suckling, feeding and swallowing (S/F/S), a key innate behavior compromised in multiple genetic developmental disorders including DiGeorge/22q11.2 Deletion Syndrome (22q11.2 DS). We combined rapid in vivo labeling of single CN V axons in LgDel^+/− mouse embryos, a genomically accurate 22q11.2DS model, and 3D imaging to identify and quantify phenotypes that could not be resolved using existing methods. We assessed these phenotypes in three 22q11.2-related genotypes to determine whether individual CN V motor and sensory axons wander, branch and sprout aberrantly in register with altered anterior–posterior hindbrain patterning and gross morphological disruption of CN V seen in LgDel^+/−. In the additional 22q11.2-related genotypes: Tbx1^+/−, Ranbp1^−/−, Ranbp1^+/− and LgDel^+/−:Raldh2^+/−; axon phenotypes are seen when hindbrain patterning and CN V gross morphology is altered, but not when it is normal or restored toward WT. This disordered growth of CN V sensory and motor axons, whose appropriate targeting is critical for optimal S/F/S, may be an early, critical determinant of imprecise innervation leading to inefficient oropharyngeal function associated with 22q11.2 deletion from birth onward.

An Integrated Perspective of Evolution and Development: From Genes to Function to Ear, Lateral Line and Electroreception

Four sensory systems (vestibular, lateral line, electroreception, auditory) are unique and project exclusively to the brainstem of vertebrates. All sensory neurons depend on a common set of genes (Eya1, Sox2, Neurog1, Neurod1) that project to a dorsal nucleus and an intermediate nucleus, which differentiate into the vestibular ear, lateral line and electroreception in vertebrates. In tetrapods, a loss of two sensory systems (lateral line, electroreception) leads to the development of a unique ear and auditory system in amniotes. Lmx1a/b, Gdf7, Wnt1/3a, BMP4/7 and Atoh1 define the lateral line, electroreception and auditory nuclei. In contrast, vestibular nuclei depend on Neurog1/2, Ascl1, Ptf1a and Olig3, among others, to develop an independent origin of the vestibular nuclei. A common origin of hair cells depends on Eya1, Sox2 and Atoh1, which generate the mechanosensory cells. Several proteins define the polarity of hair cells in the ear and lateral line. A unique connection of stereocilia requires CDH23 and PCDH15 for connections and TMC1/2 proteins to perceive mechanosensory input. Electroreception has no polarity, and a different system is used to drive electroreceptors. All hair cells function by excitation via ribbons to activate neurons that innervate the distinct target areas. An integrated perspective is presented to understand the gain and loss of different sensory systems.

A unique bipartite Polycomb signature regulates stimulus-response transcription during development

Rapid cellular responses to environmental stimuli are fundamental for development and maturation. Immediate early genes can be transcriptionally induced within minutes in response to a variety of signals. How their induction levels are regulated and their untimely activation by spurious signals prevented during development is poorly understood. We found that in developing sensory neurons, before perinatal sensory-activity-dependent induction, immediate early genes are embedded into a unique bipartite Polycomb chromatin signature, carrying active H3K27ac on promoters but repressive Ezh2-dependent H3K27me3 on gene bodies. This bipartite signature is widely present in developing cell types, including embryonic stem cells. Polycomb marking of gene bodies inhibits mRNA elongation, dampening productive transcription, while still allowing for fast stimulus-dependent mark removal and bipartite gene induction. We reveal a developmental epigenetic mechanism regulating the rapidity and amplitude of the transcriptional response to relevant stimuli, while preventing inappropriate activation of stimulus-response genes.

Why Does the Face Predict the Brain? Neural Crest Induction, Craniofacial Morphogenesis, and Neural Circuit Development

Mesenchephalic and rhombencephalic neural crest cells generate the craniofacial skeleton, special sensory organs, and subsets of cranial sensory receptor neurons. They do so while preserving the anterior-posterior (A-P) identity of their neural tube origins. This organizational principle is paralleled by central nervous system circuits that receive and process information from facial structures whose A-P identity is in register with that in the brain. Prior to morphogenesis of the face and its circuits, however, neural crest cells act as "inductive ambassadors" from distinct regions of the neural tube to induce differentiation of target craniofacial domains and establish an initial interface between the brain and face. At every site of bilateral, non-axial secondary induction, neural crest constitutes all or some of the mesenchymal compartment for non-axial mesenchymal/epithelial (M/E) interactions. Thus, for epithelial domains in the craniofacial primordia, aortic arches, limbs, the spinal cord, and the forebrain (Fb), neural crest-derived mesenchymal cells establish local sources of inductive signaling molecules that drive morphogenesis and cellular differentiation. This common mechanism for building brains, faces, limbs, and hearts, A-P axis specified, neural crest-mediated M/E induction, coordinates differentiation of distal structures, peripheral neurons that provide their sensory or autonomic innervation in some cases, and central neural circuits that regulate their behavioral functions. The essential role of this neural crest-mediated mechanism identifies it as a prime target for pathogenesis in a broad range of neurodevelopmental disorders. Thus, the face and the brain "predict" one another, and this mutual developmental relationship provides a key target for disruption by developmental pathology.

Distinct subpopulations of mechanosensory chordotonal organ neurons elicit grooming of the fruit fly antennae

Diverse mechanosensory neurons detect different mechanical forces that can impact animal behavior. Yet our understanding of the anatomical and physiological diversity of these neurons and the behaviors that they influence is limited. We previously discovered that grooming of the Drosophila melanogaster antennae is elicited by an antennal mechanosensory chordotonal organ, the Johnston's organ (JO) (Hampel et al., 2015). Here, we describe anatomically and physiologically distinct JO mechanosensory neuron subpopulations that each elicit antennal grooming. We show that the subpopulations project to different, discrete zones in the brain and differ in their responses to mechanical stimulation of the antennae. Although activation of each subpopulation elicits antennal grooming, distinct subpopulations also elicit the additional behaviors of wing flapping or backward locomotion. Our results provide a comprehensive description of the diversity of mechanosensory neurons in the JO, and reveal that distinct JO subpopulations can elicit both common and distinct behavioral responses.

Neuronal Circuits in Barrel Cortex for Whisker Sensory Perception

The array of whiskers on the snout provides rodents with tactile sensory information relating to the size, shape and texture of objects in their immediate environment. Rodents can use their whiskers to detect stimuli, distinguish textures, locate objects and navigate. Important aspects of whisker sensation are thought to result from neuronal computations in the whisker somatosensory cortex (wS1). Each whisker is individually represented in the somatotopic map of wS1 by an anatomical unit named a 'barrel' (hence also called barrel cortex). This allows precise investigation of sensory processing in the context of a well-defined map. Here, we first review the signaling pathways from the whiskers to wS1, and then discuss current understanding of the various types of excitatory and inhibitory neurons present within wS1. Different classes of cells can be defined according to anatomical, electrophysiological and molecular features. The synaptic connectivity of neurons within local wS1 microcircuits, as well as their long-range interactions and the impact of neuromodulators, are beginning to be understood. Recent technological progress has allowed cell-type-specific connectivity to be related to cell-type-specific activity during whisker-related behaviors. An important goal for future research is to obtain a causal and mechanistic understanding of how selected aspects of tactile sensory information are processed by specific types of neurons in the synaptically connected neuronal networks of wS1 and signaled to downstream brain areas, thus contributing to sensory-guided decision-making.

Orally administered oxytocin alters brain activation and behaviors of pre-weaning mice

Oxytocin (OXT) regulates adult social behavior and has been implicated in its development. Because mammalian milk contains OXT and we have recently identified OXT receptors (OXTR) in the face and oronasal cavity of pre-weaning mice, we hypothesize that orally applied OXT may impact brain activity and acute behavior in developing mice. Oral OXT may have effects in the absence of sensory stimulation or perhaps by modulating sensory input, such as whisker stimulation. The present study investigates the acute c-Fos response in the paraventricular nucleus of the hypothalamus (PVN) and along whisker sensory processing brain regions (trigeminothalamocortical circuit) to orally applied OXT, compared to saline, with and without whisker stimulation in postnatal day (P) 14 and P21 male and female mice. Acute behavioral responses were also quantified after oral OXT with whisker stimulation in a non-social context. Oral OXT with and without whisker stimulation increased c-Fos activity in the PVN of males and decreased c-Fos in the ventroposterior medial thalamus in both males and females compared to saline. Additionally, oral OXT with whisker stimulation decreased c-Fos activity across whisker sensory processing brain regions in males and females and decreased c-Fos activity in the trigeminal motor nucleus of females. Lastly, oral OXT with whisker stimulation increased males' locomotor behavior and decreased females' oromotor behavior compared to saline-treated controls. These data indicate that orally applied OXT has acute brain and behavioral effects on developing mice. OXT-modulated sensory signals may bias brain and behavior development toward the social world.

Early recovery of neuronal functioning in the sensory cortex after nerve reconstruction surgery

BACKGROUND

Nerve reconstructive surgery induces a transient loss and a prolonged and a gradual return of sensory inputs to the brain. It is unknown whether, following this massive peripheral denervation, the brain will experience a prolonged period of severe, intrinsic dysfunction.

OBJECTIVE

We aim to investigate the mechanisms of return of processing function in cortical neurons.

METHODS

We used the whisker model in rats to evaluate the functional recovery in the somatosensory cortex after a nerve reconstruction surgery. Multi-unit recording in the barrel cortex was performed in lightly anesthetized rats while their whiskers were stimulated by a whisker stimulator.

RESULTS

We observed a loss of neuronal responses to whisker stimulation 1 week after surgery, which started to recover 2 weeks after surgery. Following the surgery, only 11.8% of units had principle whiskers (PWs) returned to their original status while 17.7% had PWs different from their original status, indicating the effect of aberrant reinnervation on the whisker response map.

CONCLUSIONS

Robust neuronal responses to sensory stimulation even when only sparse sensory inputs are available in the early recovery phase. During this phase, aberrant reinnervation induces disorganized whisker tuning, a finding that might be account for the hypoesthesia and paresthesia during early recovery after nerve reconstruction.

Microglia in the Primary Somatosensory Barrel Cortex Mediate Trigeminal Neuropathic Pain

Trigeminal neuropathic pain (TGN) is an attacking, abrupt, electric-shock headache involving abnormal cortical activity. The neural mechanism underlying TGN remains elusive. In this study, we explored the role of microglia in the primary somatosensory barrel cortex (S1BF), which is a critical region for TGN, of a mouse model of TGN that displayed significant pain-related behaviors. Using electrophysiological recordings, we found robust neuronal hyperactivity in glutamatergic neurons of S1BF (Glu^S1BF). Chemogenetic inhibition of Glu^S1BF neurons significantly relieved mechanical allodynia in TGN mice. In naïve mice, chemogenetic activation of Glu^S1BF neurons induced pain sensitization. In addition, we found that microglia in the S1BF (microglia^S1BF) were significantly activated, with density and morphology changes. Intraperitoneal administration of minocycline, a microglia inhibitor, attenuated pain sensitization, and decreased Glu^S1BF neuronal activity. Together, these findings demonstrate the putative importance of microglia as a key regulator in TGN through actions on Glu^S1BF neuronal adaptation.

Primary sensory map formations reflect unique needs and molecular cues specific to each sensory system

Interaction with the world around us requires extracting meaningful signals to guide behavior. Each of the six mammalian senses (olfaction, vision, somatosensation, hearing, balance, and taste) has a unique primary map that extracts sense-specific information. Sensory systems in the periphery and their target neurons in the central nervous system develop independently and must develop specific connections for proper sensory processing. In addition, the regulation of sensory map formation is independent of and prior to central target neuronal development in several maps. This review provides an overview of the current level of understanding of primary map formation of the six mammalian senses. Cell cycle exit, combined with incompletely understood molecules and their regulation, provides chemoaffinity-mediated primary maps that are further refined by activity. The interplay between cell cycle exit, molecular guidance, and activity-mediated refinement is the basis of dominance stripes after redundant organ transplantations in the visual and balance system. A more advanced level of understanding of primary map formation could benefit ongoing restoration attempts of impaired senses by guiding proper functional connection formations of restored sensory organs with their central nervous system targets.

Topographic Maps: Motor Axons Wait Their Turn

Topographic maps are a basic organizational feature of nervous systems, and their construction involves both spatial and temporal cues. A recent study reports a novel mechanism of topographic map formation which relies on the timing of axon initiation.

Layer-specific connectivity revealed by diffusion-weighted functional MRI in the rat thalamocortical pathway

Investigating neural activity from a global brain perspective in-vivo has been in the domain of functional Magnetic Resonance Imaging (fMRI) over the past few decades. The intricate neurovascular couplings that govern fMRI's blood-oxygenation-level-dependent (BOLD) functional contrast are invaluable in mapping active brain regions, but they also entail significant limitations, such as non-specificity of the signal to active foci. Diffusion-weighted functional MRI (dfMRI) with relatively high diffusion-weighting strives to ameliorate this shortcoming as it offers functional contrasts more intimately linked with the underlying activity. Insofar, apart from somewhat smaller activation foci, dfMRI's contrasts have not been convincingly shown to offer significant advantages over BOLD-driven fMRI, and its activation maps relied on significant modelling. Here, we study whether dfMRI could offer a better representation of neural activity in the thalamocortical pathway compared to its (spin-echo (SE)) BOLD counterpart. Using high-end forepaw stimulation experiments in the rat at 9.4 T, and with significant sensitivity enhancements due to the use of cryocoils, we show for the first time that dfMRI signals exhibit layer specificity, and, additionally, display signals in areas devoid of SE-BOLD responses. We find that dfMRI signals in the thalamocortical pathway cohere with each other, namely, dfMRI signals in the ventral posterolateral (VPL) thalamic nucleus cohere specifically with layers IV and V in the somatosensory cortex. These activity patterns are much better correlated (compared with SE-BOLD signals) with literature-based electrophysiological recordings in the cortex as well as thalamus. All these findings suggest that dfMRI signals better represent the underlying neural activity in the pathway. In turn, these advanatages may have significant implications towards a much more specific and accurate mapping of neural activity in the global brain in-vivo.

Barrelette map formation in the prenatal mouse brainstem

The rodent whiskers are topographically mapped in brainstem sensory nuclei as neuronal modules known as barrelettes. Little is known about how the facial whisker pattern is copied into a brainstem barrelette topographic pattern, which serves as a template for the establishment of thalamic barreloid and, in turn, cortical barrel maps, and how precisely is the whisker pattern mapped in the brainstem during prenatal development. Here, we review recent insights advancing our understanding of the intrinsic and extrinsic patterning mechanisms contributing to establish topographical equivalence between the facial whisker pattern and the mouse brainstem during prenatal development and their relative importance.

Social touch during development: Long-term effects on brain and behavior

In this paper, our goal is to explore what is known about the role of social touch during development. We first address the neural substrates of social touch and the role of tactile experience in neural development. We discuss natural variation in early exposure to social touch, followed by a discussion on experimental manipulations of social touch during development and "natural experiments", such as early institutionalization. We then consider the role of other developmental and experiential variables that predict social touch in adults. Throughout, we propose and consider new theoretical models of the role of social touch during development on later behavior and neurobiology.

Neural coding: A single neuron's perspective

What any sensory neuron knows about the world is one of the cardinal questions in Neuroscience. Information from the sensory periphery travels across synaptically coupled neurons as each neuron encodes information by varying the rate and timing of its action potentials (spikes). Spatiotemporally correlated changes in this spiking regimen across neuronal populations are the neural basis of sensory representations. In the somatosensory cortex, however, spiking of individual (or pairs of) cortical neurons is only minimally informative about the world. Recent studies showed that one solution neurons implement to counteract this information loss is adapting their rate of information transfer to the ongoing synaptic activity by changing the membrane potential at which spike is generated. Here we first introduce the principles of information flow from the sensory periphery to the primary sensory cortex in a model sensory (whisker) system, and subsequently discuss how the adaptive spike threshold gates the intracellular information transfer from the somatic post-synaptic potential to action potentials, controlling the information content of communication across somatosensory cortical neurons.

Pterygoid Hamular Bursitis: A Possible Link to Craniofacial Pain

A striking feature of the skull base is the pterygoid hamulus known for its bizarre morphology and biomechanical location. Pterygoid hamular bursitis is an inflammation of bursae located between the tendon, muscle, and bony prominences. The minimal objective finding in an apparently normal orofacial apparatus and dependence on the subjective symptoms experienced by the patient with widespread referral pattern often perplexes the clinician. Bursitis should be considered in the differential diagnosis of craniofacial neuralgia, temporomandibular joint dysfunction, and chronic craniofacial pain. Clinical signs and symptoms of this intriguing entity are diverse and multifaceted that can sometimes demand services of clinicians across various specialties considering the anatomic density of the region. Care must be taken to avoid delay, misdiagnosis, and overtreatment.

Loss of Axon Bifurcation in Mesencephalic Trigeminal Neurons Impairs the Maximal Biting Force in Npr2-Deficient Mice

Bifurcation of axons from dorsal root ganglion (DRG) and cranial sensory ganglion (CSG) neurons is mediated by a cGMP-dependent signaling pathway composed of the ligand C-type natriuretic peptide (CNP), the receptor guanylyl cyclase Npr2 and the cGMP-dependent protein kinase I (cGKI). Here, we demonstrate that mesencephalic trigeminal neurons (MTN) which are the only somatosensory neurons whose cell bodies are located within the CNS co-express Npr2 and cGKI. Afferents of MTNs form Y-shaped branches in rhombomere 2 where the ligand CNP is expressed. Analyzing mouse mutants deficient for CNP or Npr2 we found that in the absence of CNP-induced cGMP signaling MTN afferents no longer bifurcate and instead extend either into the trigeminal root or caudally in the hindbrain. Since MTNs provide sensory information from jaw closing muscles and periodontal ligaments we measured the bite force of conditional mouse mutants of Npr2 (Npr2^flox/flox;Engr1^Cre ) that lack bifurcation of MTN whereas the bifurcation of trigeminal afferents is normal. Our study revealed that the maximal biting force of both sexes is reduced in Npr2^flox/flox;Engr1^Cre mice as compared to their Npr2^flox/flox littermate controls. In conclusion sensory feedback mechanisms from jaw closing muscles or periodontal ligaments might be impaired in the absence of MTN axon bifurcation.

Development of tactile sensory circuits in the CNS

Molecular identification of neuronal types and genetic and imaging approaches to characterize their properties reveal morphological, physiological and dynamic aspects of sensory circuit development. Here we focus on the mouse tactile sensory circuitry, with particular emphasis on the main trigeminal pathway that connects the whiskers, the major tactile organ in rodents, to the neocortex. At each level of this pathway, neurogenesis, axonal elongation, pathfinding, target recognition and circuit reorganization including dendritic refinement of cortical layer 4 neurons occur contemporaneously and a multitude of molecular signals are used in differing combinations. We highlight recent advances in development of tactile circuitry and note gaps in our understanding.

Large-scale forward genetics screening identifies Trpa1 as a chemosensor for predator odor-evoked innate fear behaviors

Innate behaviors are genetically encoded, but their underlying molecular mechanisms remain largely unknown. Predator odor 2,4,5-trimethyl-3-thiazoline (TMT) and its potent analog 2-methyl-2-thiazoline (2MT) are believed to activate specific odorant receptors to elicit innate fear/defensive behaviors in naive mice. Here, we conduct a large-scale recessive genetics screen of ethylnitrosourea (ENU)-mutagenized mice. We find that loss of Trpa1, a pungency/irritancy receptor, diminishes TMT/2MT and snake skin-evoked innate fear/defensive responses. Accordingly, Trpa1 -/- mice fail to effectively activate known fear/stress brain centers upon 2MT exposure, despite their apparent ability to smell and learn to fear 2MT. Moreover, Trpa1 acts as a chemosensor for 2MT/TMT and Trpa1-expressing trigeminal ganglion neurons contribute critically to 2MT-evoked freezing. Our results indicate that Trpa1-mediated nociception plays a crucial role in predator odor-evoked innate fear/defensive behaviors. The work establishes the first forward genetics screen to uncover the molecular mechanism of innate fear, a basic emotion and evolutionarily conserved survival mechanism.

In vitro formation of the Merkel cell-neurite complex in embryonic mouse whiskers using organotypic co-cultures

A Merkel cell-neurite complex is a touch receptor composed of specialized epithelial cells named Merkel cells and peripheral sensory nerves in the skin. Merkel cells are found in touch-sensitive skin components including whisker follicles. The nerve fibers that innervate Merkel cells of a whisker follicle extend from the maxillary branch of the trigeminal ganglion. Whiskers as a sensory organ attribute to the complicated architecture of the Merkel cell-neurite complex, and therefore it is intriguing how the structure is formed. However, observing the dynamic process of the formation of a Merkel cell-neurite complex in whiskers during embryonic development is still difficult. In this study, we tried to develop an organotypic co-culture method of a whisker pad and a trigeminal ganglion explant to form the Merkel cell-neurite complex in vitro. We initially developed two distinct culture methods of a single whisker row and a trigeminal ganglion explant, and then combined them. By dissecting and cultivating a single row from a whisker pad, the morphogenesis of whisker follicles could be observed under a microscope. After the co-cultivation of the whisker row with a trigeminal ganglion explant, a Merkel cell-neurite complex composed of Merkel cells, which were positive for both cytokeratin 8 and SOX2, Neurofilament-H-positive trigeminal nerve fibers and Schwann cells expressing Nestin, SOX2 and SOX10 was observed via immunohistochemical analyses. These results suggest that the process for the formation of a Merkel cell-neurite complex can be observed under a microscope using our organotypic co-culture method.

Constraints on somatosensory map development: mutants lead the way

In the rodent somatosensory system, the disproportionally large whisker representation and their specialization into barrel-shaped units in the different sensory relays has offered experimentalists with an ideal tool to identify mechanisms involved in brain map formation. These combine three intertwined constraints: Firstly, fasciculation of the incoming axons; secondly, early neural activity; finally, molecular patterning. Sophisticated genetic manipulations in mice have now allowed dissecting these mechanisms with greater accuracy. Here we discuss some recent papers that provided novel insights into how these different mapping rules and constraints interact to shape the barrel map.

Neurons within the trigeminal mesencephalic nucleus encode for the kinematic parameters of the whisker pad macrovibrissae

It has been recently shown in rats that spontaneous movements of whisker pad macrovibrissae elicited evoked responses in the trigeminal mesencephalic nucleus (Me5). In the present study, electrophysiological and neuroanatomical experiments were performed in anesthetized rats to evaluate whether, besides the whisker displacement per se, the Me5 neurons are also involved in encoding the kinematic properties of macrovibrissae movements, and also whether, as reported for the trigeminal ganglion, even within the Me5 nucleus exists a neuroanatomical representation of the whisker pad macrovibrissae. Extracellular electrical activity of single Me5 neurons was recorded before, during, and after mechanical deflection of the ipsilateral whisker pad macrovibrissae in different directions, and with different velocities and amplitudes. In several groups of animals, single or multiple injections of the tracer Dil were performed into the whisker pad of one side, in close proximity to the vibrissae follicles, in order to label the peripheral terminals of the Me5 neurons innervating the macrovibrissae (whisking‐neurons), and therefore, the respective perikaria within the nucleus. Results showed that: (1) the whisker pad macrovibrissae were represented in the medial‐caudal part of the Me5 nucleus by a single cluster of cells whose number seemed to match that of the macrovibrissae; (2) macrovibrissae mechanical deflection elicited significant responses in the Me5 whisking‐neurons, which were related to the direction, amplitude, and frequency of the applied deflection. The specific functional role of Me5 neurons involved in encoding proprioceptive information arising from the macrovibrissae movements is discussed within the framework of the whole trigeminal nuclei activities.

Zebrafish and medaka offer insights into the neurobehavioral correlates of vertebrate magnetoreception

An impediment to a mechanistic understanding of how some species sense the geomagnetic field ("magnetoreception") is the lack of vertebrate genetic models that exhibit well-characterized magnetoreceptive behavior and are amenable to whole-brain analysis. We investigated the genetic model organisms zebrafish and medaka, whose young stages are transparent and optically accessible. In an unfamiliar environment, adult fish orient according to the directional change of a magnetic field even in darkness. To enable experiments also in juveniles, we applied slowly oscillating magnetic fields, aimed at generating conflicting sensory inputs during exploratory behavior. Medaka (but not zebrafish) increase their locomotor activity in this assay. Complementary brain  activity mapping reveals neuronal activation in the lateral hindbrain during magnetic stimulation. These comparative data support magnetoreception in teleosts, provide evidence for a light-independent mechanism, and demonstrate the usefulness of zebrafish and medaka as genetic vertebrate models for studying the biophysical and neuronal mechanisms underlying magnetoreception.

Exosomes: Nanocarriers of Biological Messages

Cell-cell communication is crucial to maintain homeostasis in multicellular organism. Cells communicate each other by direct contact or by releasing factors that, soluble or packaged in membrane vesicles, can reach different regions of the organism. To date numerous studies highlighted the existence of several types of extracellular vesicles that, differing for dimension, origin and contents, play a role in physiological and/or pathological processes. Among extracellular vesicles, exosomes are emerging as efficient players to modulate target cells phenotype and as new non-invasive diagnostic and prognostic tools in multiple diseases. They, in fact, strictly reflect the type and functional status of the producing cells and are able to deliver their contents even over a long distance. The results accumulated in the last two decades and collected in this chapter, indicated that exosomes, can carry RNAs, microRNAs, long non-coding RNAs, DNA, lipids, metabolites and proteins; a deeper understanding of their contents is therefore needed to get the most from this incredible cell product.

MicroRNA Networks in Breast Cancer Cells

A variety of molecular techniques can be used in order to unravel the molecular composition of cells. In particular, the microarray technology has been used to identify novel biomarkers that may be useful in the diagnosis, prognosis, or treatment of cancer. The microarray technology is ideal for biomarker discovery as it allows for the screening of a large number of molecules at once. In this review, we focus on microRNAs (miRNAs) which are key molecules in cells and regulate gene expression post-transcriptionally. miRNAs are small, single-stranded RNA molecules that bind to complementary mRNAs. Binding of miRNAs to mRNAs leads either to degradation, or translational inhibition of the target mRNA. Roughly one third of all the mRNAs are postulated to be regulated by miRNAs. miRNAs are known to be deregulated in different types of cancer, including breast cancer, and it has been demonstrated that deregulation of several miRNAs can be used as biological markers in cancer. miRNA expression can for example discriminate between normal, benign and malignant breast tissue, and between different breast cancer subtypes.In the post-genomic era, an important task of molecular biology is to understand gene regulation in the context of biological networks. Because miRNAs have such a pronounced role in cells, it is pivotal to understand the mechanisms that underlie their control, and to identify how miRNAs influence cancer development and progression.

Inflammation-associated microRNA changes in circulating exosomes of heart failure patients

Objective

MiR-486 and miR-146a are cardiomyocyte-enriched microRNAs that control cell survival and self-regulation of inflammation. These microRNAs are released into circulation and are detected in plasma or in circulating exosomes. Little is known whether heart failure affects their release into circulation, which this study investigated.

Results

Total and exosome-specific microRNAs in plasma of 40 heart failure patients and 20 controls were prepared using the miRVana Kit. We measured exosomal and total plasma microRNAs separately because exosomes serve as cargos that transfer biological materials and alter signaling in distant organs, whereas microRNAs in plasma indicate the level of tissue damage and are mostly derived from dead cells. qRT-PCR was used to quantify miR-486, miR-146a, and miR-16. Heart failure did not significantly affect plasma miR-486/miR-16 and miR-146a/miR-16 ratio, although miR-146a/miR-16 showed a trend of elevated expression (2.3 ± 0.79, p = 0.27). By contrast, circulating exosomal miR-146a/miR-16 ratio was higher in heart failure patients (2.46 ± 0.51, p = 0.05). miR-146a is induced in response to inflammation as a part of inflammation attenuation circuitry. Indeed, Tnfα and Gm-csf increased miR-146a but not miR-486 in the cardiomyocyte cell line H9C2. These results, if confirmed in a larger study, may help to develop circulating exosomal miR-146a as a biomarker of heart failure.

Nervous system disruption and swimming abnormality in early-hatched pufferfish (Takifugu niphobles) larvae caused by pyrene is independent of aryl hydrocarbon receptors

Pyrene, a member of the polycyclic aromatic hydrocarbons (PAHs), contributes to abnormality in the size of the brain and the swimming behavior of pufferfish (Takifugu niphobles) larvae. We hypothesized that the aryl hydrocarbon receptor (AHR) may mediate pyrene-induced toxic effects because AHR is assumed to be a candidate for the downstream target of PAHs in many cases. To identify the contribution of AHR on developing pufferfish, we performed exposure experiments using β-naphthoflavone, an agonist of AHR. We found that the toxic effects of pyrene and β-naphthoflavone in pufferfish larvae are fundamentally different. Pyrene specifically induced problems in the developing midbrain and in swimming behavior, while β-naphthoflavone affected the heartbeat rate and the size of the yolk. These results suggest that the behavioral and morphological abnormality caused by pyrene exposure is mediated by an AHR-independent pathway. Alternatively, defects caused by pyrene may be attributed to the inhibition of the FGF signal.

miRNAs in bone metastasis

Bone metastasis is one of the most common forms of metastasis from a number of different primary carcinomas. MicroRNAs (miRNAs) are short, endogenous RNAs that negatively regulate gene expression to control essential pathways, including those involved in bone organogenesis and homeostasis. As these pathways are often hijacked during bone metastasis, it is not surprising that miRNAs can also influence bone metastasis formation. Areas covered: In this review, we first summarize the major signalling pathways involved in normal bone development and bone metastasis. We will then discuss the overall roles of miRNAs in cancer metastasis and highlight the recent findings on the effects of miRNAs in bone metastasis. To this aim, we have performed a literature search in PubMed by using the search words 'miRNAs' and 'bone metastasis', selecting relevant scientific articles published between 2010 and 2016. Seminal publications before 2010 on the metastatic role of miRNAs have also been considered. Expert commentary: With the lack of current diagnostic biomarkers and effective targeted therapies for bone metastasis, the significant role of miRNAs in the regulation of bone homeostasis and bone metastasis may support the future use of miRNAs as diagnostic biomarkers and therapeutic targets.

Somatotopy in the Medullary Dorsal Horn As a Basis for Orofacial Reflex Behavior

The somatotopy of the trigeminocervical complex of the rat was defined as a basis for describing circuitry for reflex behaviors directed through the facial motor nucleus. Thus, transganglionic transport of horseradish peroxidase conjugates applied to individual nerves/peripheral receptive fields showed that nerves innervating oropharyngeal structures projected most rostrally, followed by nerves innervating snout, periocular, and then periauricular receptive fields most caudally. Nerves innervating mucosae or glabrous receptive fields terminated densely in laminae I, II, and V of the trigeminocervical complex, while those innervating hairy skin terminated in laminae I-V. Projections to lamina II exhibited the most focused somatotopy when individual cases were compared. Retrograde transport of FluoroGold (FG) deposited into the facial motor nucleus resulted in labeled neurons almost solely in lamina V of the trigeminocervical complex. The distribution of these labeled neurons paralleled the somatotopy of primary afferent fibers, e.g., those labeled after FG injections into a functional group of motoneurons innervating lip musculature were found most rostrally while those labeled after injections into motoneurons innervating snout, periocular and preauricular muscles, respectively, were found at progressively more caudal levels. Anterograde transport of injections of biotinylated dextran amine into lamina V at different rostrocaudal levels of the trigeminocervical complex confirmed the notion that the somatotopy of orofacial sensory fields parallels the musculotopy of facial motor neurons. These data suggest that neurons in lamina V are important interneurons in a simple orofacial reflex circuit consisting of a sensory neuron, interneuron and motor neuron. Moreover, the somatotopy of primary afferent fibers from the head and neck confirms the "onion skin hypothesis" and suggests rostral cervical dermatomes blend seamlessly with "cranial dermatomes." The transition area between subnucleus interpolaris and subnucleus caudalis is addressed while the paratrigeminal nucleus is discussed as an interface between the somatic and visceral nervous systems.

In vivo validation of metastasis-regulating microRNA-766 in human triple-negative breast cancer cells

Breast cancer is the second most common cancer and the most frequent cancer in women worldwide. Recent improvements in early detection and effective adjuvant chemotherapies have improved the survival of breast cancer patients. Even with initial disease remission, one-third of all breast cancer patients will relapse with distant metastasis. Breast cancer metastasis is largely an incurable disease and the main cause of death among breast cancer patients. Cancer metastasis is comprised of complex processes that are usually not controllable by intervention of a single molecular target. As a single microRNA (miRNA) can affect the aggressiveness of breast cancer cells by concurrently modulating multiple pathway effectors, a metastasis-regulating miRNA would represent a good disease target candidate. In this study, we evaluated the functional capacity of a newly defined human metastasis-related miRNA, miR-766, which was previously identified by comparing a patient-derived xenograft primary tumor model and a metastasis model. Compared to vector-transfected control cells, miR-766-overexpressed triple-negative breast cancer cells exhibited similar primary tumor growth in the orthotopic xenograft model. In contrast, tumor sphere formation and Matrigel invasion were significantly decreased in miR-766-overexpressed breast cancer cells compared with control cancer cells. In addition, lung metastasis was dramatically reduced in miR-766-overexpressed breast cancer cells compared with control cells. Thus, miR-766 affected the distant metastasis process to a greater extent than cancer cell proliferation and primary tumor growth, and may represent a future therapeutic target to effectively control fatal breast cancer metastasis.

The Molecular Fingerprint of Dorsal Root and Trigeminal Ganglion Neurons

The dorsal root ganglia (DRG) and trigeminal ganglia (TG) are clusters of cell bodies of highly specialized sensory neurons which are responsible for relaying information about our environment to the central nervous system. Despite previous efforts to characterize sensory neurons at the molecular level, it is still unknown whether those present in DRG and TG have distinct expression profiles and therefore a unique molecular fingerprint. To address this question, we isolated lumbar DRG and TG neurons using fluorescence-activated cell sorting from Advillin-GFP transgenic mice and performed RNA sequencing. Our transcriptome analyses showed that, despite being overwhelmingly similar, a number of genes are differentially expressed in DRG and TG neurons. Importantly, we identified 24 genes which were uniquely expressed in either ganglia, including an arginine vasopressin receptor and several homeobox genes, giving each population a distinct molecular fingerprint. We compared our findings with published studies to reveal that many genes previously reported to be present in neurons are in fact likely to originate from other cell types in the ganglia. Additionally, our neuron-specific results aligned well with a dataset examining whole human TG and DRG. We propose that the data can both improve our understanding of primary afferent biology and help contribute to the development of drug treatments and gene therapies which seek targets with unique or restricted expression patterns.

Fate and freedom in developing neocortical circuits

The activity of neuronal circuits of the neocortex underlies our ability to perceive the world and interact with our environment. During development, these circuits emerge from dynamic interactions between cell-intrinsic, genetically determined programs and input/activity-dependent signals, which together shape these circuits into adulthood. Building on a large body of experimental work, several recent technological developments now allow us to interrogate these nature–nurture interactions with single gene/single input/single-cell resolution. Focusing on excitatory glutamatergic neurons, this review discusses the genetic and input-dependent mechanisms controlling how individual cortical neurons differentiate into specialized cells to assemble into stereotypical local circuits within global, large-scale networks.

Proper functioning of the neocortex – the center of higher-order brain functions – depends on the correct assembly of neocortical neural circuits during development. Here the author discusses how cell-intrinsic developmental programs and activity-dependent signals together shape the formation of neocortical circuits.

MicroRNA-338 Attenuates Cortical Neuronal Outgrowth by Modulating the Expression of Axon Guidance Genes

MicroRNAs (miRs) are small non-coding RNAs that confer robustness to gene networks through post-transcriptional gene regulation. Previously, we identified miR-338 as a modulator of axonal outgrowth in sympathetic neurons. In the current study, we examined the role of miR-338 in the development of cortical neurons and uncovered its downstream mRNA targets. Long-term inhibition of miR-338 during neuronal differentiation resulted in reduced dendritic complexity and altered dendritic spine morphology. Furthermore, monitoring axon outgrowth in cortical cells revealed that miR-338 overexpression decreased, whereas inhibition of miR-338 increased axonal length. To identify gene targets mediating the observed phenotype, we inhibited miR-338 in cortical neurons and performed whole-transcriptome analysis. Pathway analysis revealed that miR-338 modulates a subset of transcripts involved in the axonal guidance machinery by means of direct and indirect gene targeting. Collectively, our results implicate miR-338 as a novel regulator of cortical neuronal maturation by fine-tuning the expression of gene networks governing cortical outgrowth.

Behavioral Consequences of a Bifacial Map in the Mouse Somatosensory Cortex

The whisker system is an important sensory organ with extensive neural representations in the brain of the mouse. Patterned neural modules (barrelettes) in the ipsilateral principal sensory nucleus of the trigeminal nerve (PrV) correspond to the whiskers. Axons of the PrV barrelette neurons cross the midline and confer the whisker-related patterning to the contralateral ventroposteromedial nucleus of the thalamus, and subsequently to the cortex. In this way, specific neural modules called barreloids and barrels in the contralateral thalamus and cortex represent each whisker. Partial midline crossing of the PrV axons, in a conditional Robo3 mutant (Robo3^R3-5cKO) mouse line, leads to the formation of bilateral whisker maps in the ventroposteromedial, as well as the barrel cortex. We used voltage-sensitive dye optical imaging and somatosensory and motor behavioral tests to characterize the consequences of bifacial maps in the thalamocortical system. Voltage-sensitive dye optical imaging verified functional, bilateral whisker representation in the barrel cortex and activation of distinct cortical loci following ipsilateral and contralateral stimulation of the specific whiskers. The mutant animals were comparable with the control animals in sensorimotor tests. However, they showed noticeable deficits in all of the whisker-dependent or -related tests, including Y-maze exploration, horizontal surface approach, bridge crossing, gap crossing, texture discrimination, floating in water, and whisking laterality. Our results indicate that bifacial maps along the thalamocortical system do not offer a functional advantage. Instead, they lead to impairments, possibly due to the smaller size of the whisker-related modules and interference between the ipsilateral and contralateral whisker representations in the same thalamus and cortex.SIGNIFICANCE STATEMENT The whisker sensory system plays a quintessentially important role in exploratory behavior of mice and other nocturnal rodents. Here, we studied a novel mutant mouse line, in which the projections from the brainstem to the thalamus are disrupted. This led to formation of bilateral whisker maps in both the thalamus and the cortex. The two whisker maps crowd in a space normally devoted to the contralateral map alone and in a nonoverlapping fashion. Stimulation of the whiskers on either side activates the corresponding region of the map. Mice with bilateral whisker maps perform well in general sensorimotor tasks but show poor performance in specific tests that require whisker-dependent tactile discrimination. These observations indicate that contralateral, instead of bilateral, representation of the sensory space plays a critical role in acuity and fine discrimination during somesthesis.

Somatosensory Modulation of Salivary Gene Expression and Oral Feeding in Preterm Infants: Randomized Controlled Trial

Background

Despite numerous medical advances in the care of at-risk preterm neonates, oral feeding still represents one of the first and most advanced neurological challenges facing this delicate population. Objective, quantitative, and noninvasive assessment tools, as well as neurotherapeutic strategies, are greatly needed in order to improve feeding and developmental outcomes. Pulsed pneumatic orocutaneous stimulation has been shown to improve nonnutritive sucking (NNS) skills in preterm infants who exhibit delayed or disordered nipple feeding behaviors. Separately, the study of the salivary transcriptome in neonates has helped identify biomarkers directly linked to successful neonatal oral feeding behavior. The combination of noninvasive treatment strategies and transcriptomic analysis represents an integrative approach to oral feeding in which rapid technological advances and personalized transcriptomics can safely and noninvasively be brought to the bedside to inform medical care decisions and improve care and outcomes.

Objective

The study aimed to conduct a multicenter randomized control trial (RCT) to combine molecular and behavioral methods in an experimental conceptualization approach to map the effects of PULSED somatosensory stimulation on salivary gene expression in the context of the acquisition of oral feeding habits in high-risk human neonates. The aims of this study represent the first attempt to combine noninvasive treatment strategies and transcriptomic assessments of high-risk extremely preterm infants (EPI) to (1) improve oral feeding behavior and skills, (2) further our understanding of the gene ontology of biologically diverse pathways related to oral feeding, (3) use gene expression data to personalize neonatal care and individualize treatment strategies and timing interventions, and (4) improve long-term developmental outcomes.

Methods

A total of 180 extremely preterm infants from three neonatal intensive care units (NICUs) will be randomized to receive either PULSED or SHAM (non-pulsing) orocutaneous intervention simultaneous with tube feedings 3 times per day for 4 weeks, beginning at 30 weeks postconceptional age. Infants will also be assessed 3 times per week for NNS performance, and multiple saliva samples will be obtained each week for transcriptomic analysis, until infants have achieved full oral feeding status. At 18 months corrected age (CA), infants will undergo neurodevelopmental follow-up testing, the results of which will be correlated with feeding outcomes in the neo-and post-natal period and with gene expression data and intervention status.

Results

The ongoing National Institutes of Health funded randomized controlled trial R01HD086088 is actively recruiting participants. The expected completion date of the study is 2021.

Conclusions

Differential salivary gene expression profiles in response to orosensory entrainment intervention are expected to lead to the development of individualized interventions for the diagnosis and management of oral feeding in preterm infants.

Trial Registration

ClinicalTrials.gov NCT02696343; https://clinicaltrials.gov/ct2/show/NCT02696343 (Archived by WebCite at http://www.webcitation.org/6r5NbJ9Ym)

From periodontal mechanoreceptors to chewing motor control: A systematic review

PURPOSE

This critical review summarizes the current knowledge of the structural and functional characteristics of periodontal mechanoreceptors, and understands their role in the signal pathways and functional motor control.

METHOD

A systematic review of the literature was conducted. Original articles were searched through Pubmed, Cochrane Central database and Embase until january 2016.

RESULT

1466 articles were identified through database searching and screened by reviewing the abstracts. 160 full-text were assessed for eligibility, and after 109 exclusion, 51 articles were included in the review process. Studies selected by the review process were mainly divided in studies on animal and studies on humans. Morphological, histological, molecular and electrophysiological studies investigating the periodontal mechanoreceptors in animals and in humans were included, evaluated and described.

CONCLUSION

Our knowledge of the periodontal mechanoreceptors, let us conclude that they are very refined neural receptors, deeply involved in the activation and coordination of the masticatory muscles during function. Strictly linked to the rigid structure of the teeth, they determine all the functional physiological and pathological processes of the stomatognathic system. The knowledge of their complex features is fundamental for all dental professionists. Further investigations are of utmost importance for guiding the technological advances in the respect of the neural control in the dental field.

MicroRNA-211 expression is down-regulated and associated with poor prognosis in human glioma

Accumulating evidence has supported the role of microRNAs in the initiation and development of malignant tumors. MicroRNA-211 (miR-211), which was reported to involve in diverse physiological activities in several cancers, was investigated for its expression in human glioma and adjacent normal brain tissues, as well as its correlation with patient prognosis. Glioma tissues and adjacent normal brain tissues were obtained from 82 patients who underwent surgical resection, and quantitative real-time polymerase chain reaction was performed to assess the expression level of miR-211. Here, we found that miR-211 was significantly decreased in glioma tissues compared with adjacent normal brain tissues (glioma, 3.52 ± 0.14 vs. normal, 4.96 ± 0.17, p < 0.001), and inversely associated with ascending WHO classification (grade III-IV, 3.16 ± 0.21 vs. grade I-II, 4.22 ± 0.26, p < 0.001). Then, the correlation of miR-211 with clinicopathological factors was investigated by Pearson's Chi square test, indicating that miR-211 might be a potential biomarker to predict the malignant status of glioma. Further, Kaplan-Meier curves with log-rank analysis were carried out to determine the relationship between miR-211 expression level and the overall survival rate of glioma patients. Our data showed that there was a close correlation between down-regulated miR-211 and shorter survival time in 82 patients (p = 0.026). Finally, the multivariate Cox regression analysis indicated that WHO grade (HR = 2.437, 95% CI 1.251-4.966, p = 0.007), KPS (HR = 2.215, 95% CI 1.168-4.259, p = 0.016), and miR-211 expression level (HR = 3.614, 95% CI 2.152-6.748, p < 0.001) were considered as independent risk factors for glioma prognosis. These results suggested that lower miR-211 expression might be a marker for poor prognosis of glioma patients.

Genetics and epigenetics of varicocele pathophysiology: an overview

Varicocele is found in approximately 20% of adults and adolescents and in 19-41% of men seeking treatment for infertility. It is associated with a decrease in sperm count as well as sperm motility and morphology. The currently accepted description of the pathophysiology of varicocele does not explain all its clinical manifestations; therefore, other factors such as genetic and epigenetic changes, associated with the environment, might be involved in causing infertility and decrease in sperm quality. It has been reported that the varicocele-induced deterioration of testicular function is progressive and interferes with fertility; hence, early and efficient assessment of the genetic manifestations in patients would be important for developing future medical interventions. Chromosomal disorders, mutations, polymorphisms, changes in gene expression, and epigenetic changes have all been reported to be associated with varicocele. Several studies are underway to unravel the genetic basis of this disease, as it is important to understand the origin and the aggravating factors to ensure appropriate guidance and intervention. Here, we review the available literature regarding the genetic and epigenetic changes associated with varicocele, and how these alterations are related to the different clinical manifestations of the disease.

An exercise in brain genoarchitectonics: Analysis of AZIN2-Lacz expressing neuronal populations in the mouse hindbrain

We examined in detail the distribution of AZIN2 (antizyme inhibitor 2) expression in the adult mouse hindbrain and neighboring spinal cord. AZIN2, similar to previously known AZIN1, is a recently-discovered, a functional paralog of ornithine decarboxylase (ODC). Due to their structural similarity to ODC, both AZIN1 and AZIN2 counteract the inhibitory action of 3 known antizymes (AZ1-3) on the ODC synthesis of polyamines, thus increasing intracytoplasmic levels of polyamines. AZIN2 is strongly, but heterogeneously, expressed in the brain. Our study uses a mouse line carrying an AZIN2-LacZ construct, and, in our topographic analysis of AZIN2-positive structures, we intend to share new knowledge about the rhombomeric segmentation of the hindbrain (a function of Hox paralogs and other genes). The observed labeled cell populations predominantly coincide with known cholinergic and glutamatergic cells, but occasionally also correspond to GABAergic, and possibly glycinergic cells. Some imperfectly known hindbrain populations stood out in unprecedented detail, and some axonal tracts were also differentially stained. © 2017 Wiley Periodicals, Inc.