Deficient pheromone responses in mice lacking a cluster of vomeronasal receptor genes

The mammalian vomeronasal organ (VNO), a part of the olfactory system, detects pheromones--chemical signals that modulate social and reproductive behaviours. But the molecular receptors in the VNO that detect these chemosensory stimuli remain undefined. Candidate pheromone receptors are encoded by two distinct and complex superfamilies of genes, V1r and V2r (refs 3 and 4), which code for receptors with seven transmembrane domains. These genes are selectively expressed in sensory neurons of the VNO. However, there is at present no functional evidence for a role of these genes in pheromone responses. Here, using chromosome engineering technology, we delete in the germ line of mice an approximately 600-kilobase genomic region that contains a cluster of 16 intact V1r genes. These genes comprise two of the 12 described V1r gene families, and represent approximately 12% of the V1r repertoire. The mutant mice display deficits in a subset of VNO-dependent behaviours: the expression of male sexual behaviour and maternal aggression is substantially altered. Electrophysiologically, the epithelium of the VNO of such mice does not respond detectably to specific pheromonal ligands. The behavioural impairment and chemosensory deficit support a role of V1r receptors as pheromone receptors.     

Sex-specific peptides from exocrine glands stimulate mouse vomeronasal sensory neurons

In mammals, social and reproductive behaviours are modulated by pheromones, which are chemical signals that convey information about sex and strain. The vomeronasal organ, located at the base of the nasal septum, is responsible for mediating pheromone information in mice. Two classes of putative pheromone receptor gene families, V1R and V2R, are expressed by vomeronasal sensory neurons in mutually segregated epithelial zones of the vomeronasal organ. Although numerous studies have suggested that pheromones originate from urine, direct recordings of behaving mice have shown that neuronal firing in the vomeronasal system is modulated by physical contact with the facial area. Here we identify a male-specific 7-kDa peptide secreted from the extraorbital lacrimal gland. This peptide, which we named exocrine gland-secreting peptide 1 (ESP1), is encoded by a gene from a previously unrecognized large family clustered in proximity to the class I major histocompatibility complex (MHC) region. ESP1 is secreted from the eyes and is transferred to the female vomeronasal organ, where it stimulates V2R-expressing vomeronasal sensory neurons and elicits an electrical response. Our results indicate that mice respond to sex-specific peptides released from exocrine glands through the vomeronasal system during direct contact.     

基于量子点荧光探针的高灵敏蛋白质检测方法

通过制备量子点荧光检测探针,构建了一种基于量子点探针和免疫磁珠的蛋白质检测方法,实现了对蛋白肿瘤标志物癌胚抗原(carcinoembryonic antigen,CEA)的高灵敏定量检测.在该检测体系中,若存在有靶标蛋白,其与量子点检测探针以及捕获探针之间会发生免疫反应形成三明治结构,利用磁力分离器对免疫复合物进行富集后,通过检测富集在磁珠表面的量子点荧光信号,可实现对靶标蛋白的定量.该方法的检测灵敏度为38 pg/mL,线性范围为0.39~50ng/mL,临床质控样本检验结果表明,该方法准确度高,可重复性好,可应用于临床样本检测.该量子点探针检测体系具有灵敏度高、特异性好、样品消耗量低等优点,在疾病早期诊断方面具有广阔的应用前景.     

Dopamine neurons modulate pheromone responses in Drosophila courtship learning

Learning through trial-and-error interactions allows animals to adapt innate behavioural ‘rules of thumb’ to the local environment, improving their prospects for survival and reproduction. Naive Drosophila melanogaster males, for example, court both virgin and mated females, but learn through experience to selectively suppress futile courtship towards females that have already mated. Here we show that courtship learning reflects an enhanced response to the male pheromone cis-vaccenyl acetate (cVA), which is deposited on females during mating and thus distinguishes mated females from virgins. Dissociation experiments suggest a simple learning rule in which unsuccessful courtship enhances sensitivity to cVA. The learning experience can be mimicked by artificial activation of dopaminergic neurons, and we identify a specific class of dopaminergic neuron that is critical for courtship learning. These neurons provide input to the mushroom body (MB) γ lobe, and the DopR1 dopamine receptor is required in MBγ neurons for both natural and artificial courtship learning. Our work thus reveals critical behavioural, cellular and molecular components of the learning rule by which Drosophila adjusts its innate mating strategy according to experience.     

ATP mediates fast synaptic transmission in mammalian neurons.

In addition to its diverse functions inside cells, ATP can act at several types of cell-surface receptor. One of these (P2X-purinoceptor) is believed to be a ligand-gated cation channel. The presence of P2X receptors on autonomic, sensory and central neurons suggests that ATP might be released to act as a fast excitatory synaptic transmitter. Here we record excitatory synaptic potentials and currents from cultured coeliac ganglion neurons which are mimicked by ATP, blocked by the P2-purinoceptor antagonist suramin, desensitized by alpha,beta-methylene-ATP and unaffected by antagonists acting at nicotine, 5-hydroxytryptamine, N-methyl-D-aspartate (NMDA), non-NMDA glutamate, gamma-aminobutyric acid (GABA), noradrenaline or adenosine receptors. We conclude that ATP is the neurotransmitter at this neuroneuronal synapse.     

Ultrasensitive polarized-light photodetectors based on 2D hybrid perovskite ferroelectric crystals with a low detection limit

Polarized-light photodetectors are the indispensable elements for practical optical and optoelectronic device applications.Two-dimensional(2D)hybrid perovskite ...     

A single class of olfactory neurons mediates behavioural responses to a Drosophila sex pheromone

Insects, like many other animals, use sex pheromones to coordinate their reproductive behaviours. Volatile pheromones are detected by odorant receptors expressed in olfactory receptor neurons (ORNs). Whereas fruit odours typically activate multiple ORN classes, pheromones are thought to act through single dedicated classes of ORN. This model predicts that activation of such an ORN class should be sufficient to trigger the appropriate behavioural response. Here we show that the Drosophila melanogaster male-specific pheromone 11-cis-vaccenyl acetate (cVA) acts through the receptor Or67d to regulate both male and female mating behaviour. Mutant males that lack Or67d inappropriately court other males, whereas mutant females are less receptive to courting males. These data suggest that cVA has opposite effects in the two sexes: inhibiting mating behaviour in males but promoting mating behaviour in females. Replacing Or67d with moth pheromone receptors renders these ORNs sensitive to the corresponding moth pheromones. In such flies, moth pheromones elicit behavioural responses that mimic the normal response to cVA. Thus, activation of a single ORN class is both necessary and sufficient to mediate behavioural responses to the Drosophila sex pheromone cVA.     

Transient cells of the developing mammalian telencephalon are peptide-immunoreactive neurons

In the development of the mammalian telencephalon, the genesis of neurons destined for the various layers of the cerebral cortex is preceded by the generation of a population of cells that comes to reside in the subplate and marginal zones (see ref. 2 for nomenclature). In the cat, these cells are present in large numbers during development, when their location is correlated with the arrival and accumulation of ingrowing axonal systems and with synapses. However, as the brain matures, the cells disappear and the white matter and layer 1 of the adult emerge. Their disappearance occurs in concert with the invasion of the cortical plate by the axonal systems and with the elimination of the synapses from the subplate. Here we report that the subplate cells have properties typical of mature neurons. They have the ultrastructural appearance of neurons and receive synaptic contacts. They also have long projections and are immunoreactive for MAP2 (microtubule associated protein 2). Further, subpopulations are immunoreactive for one of several neuropeptides. These observations suggest that during the fetal and early postnatal development of the mammalian telencephalon the subplate cells function as neurons in synaptic circuitry that disappears by adulthood.     

The cells and logic for mammalian sour taste detection

Mammals taste many compounds yet use a sensory palette consisting of only five basic taste modalities: sweet, bitter, sour, salty and umami (the taste of monosodium glutamate). Although this repertoire may seem modest, it provides animals with critical information about the nature and quality of food. Sour taste detection functions as an important sensory input to warn against the ingestion of acidic (for example, spoiled or unripe) food sources. We have used a combination of bioinformatics, genetic and functional studies to identify PKD2L1, a polycystic-kidney-disease-like ion channel, as a candidate mammalian sour taste sensor. In the tongue, PKD2L1 is expressed in a subset of taste receptor cells distinct from those responsible for sweet, bitter and umami taste. To examine the role of PKD2L1-expressing taste cells in vivo, we engineered mice with targeted genetic ablations of selected populations of taste receptor cells. Animals lacking PKD2L1-expressing cells are completely devoid of taste responses to sour stimuli. Notably, responses to all other tastants remained unaffected, proving that the segregation of taste qualities even extends to ionic stimuli. Our results now establish independent cellular substrates for four of the five basic taste modalities, and support a comprehensive labelled-line mode of taste coding at the periphery. Notably, PKD2L1 is also expressed in specific neurons surrounding the central canal of the spinal cord. Here we demonstrate that these PKD2L1-expressing neurons send projections to the central canal, and selectively trigger action potentials in response to decreases in extracellular pH. We propose that these cells correspond to the long-sought components of the cerebrospinal fluid chemosensory system. Taken together, our results suggest a common basis for acid sensing in disparate physiological settings.     

An essential role for a CD36-related receptor in pheromone detection in Drosophila

The CD36 family of transmembrane receptors is present across metazoans and has been implicated biochemically in lipid binding and transport. Several CD36 proteins function in the immune system as scavenger receptors for bacterial pathogens and seem to act as cofactors for Toll-like receptors by facilitating recognition of bacterially derived lipids. Here we show that a Drosophila melanogaster CD36 homologue, Sensory neuron membrane protein (SNMP), is expressed in a population of olfactory sensory neurons (OSNs) implicated in pheromone detection. SNMP is essential for the electrophysiological responses of OSNs expressing the receptor OR67d to (Z)-11-octadecenyl acetate (cis-vaccenyl acetate, cVA), a volatile male-specific fatty-acid-derived pheromone that regulates sexual and social aggregation behaviours. SNMP is also required for the activation of the moth pheromone receptor HR13 by its lipid-derived pheromone ligand (Z)-11-hexadecenal, but is dispensable for the responses of the conventional odorant receptor OR22a to its short hydrocarbon fruit ester ligands. Finally, we show that SNMP is required for responses of OR67d to cVA when ectopically expressed in OSNs not normally activated by pheromones. Because mammalian CD36 binds fatty acids, we suggest that SNMP acts in concert with odorant receptors to capture pheromone molecules on the surface of olfactory dendrites. Our work identifies an unanticipated cofactor for odorant receptors that is likely to have a widespread role in insect pheromone detection. Moreover, these results define a unifying model for CD36 function, coupling recognition of lipid-based extracellular ligands to signalling receptors in both pheromonal communication and pathogen recognition through the innate immune system.     

Induction of yeast mating pheromone a-factor by alpha cells

Saccharomyces cerevisiae cells of a and alpha mating types constitutively secrete cell-specific peptide mating pheromones. a-Factor is secreted by a cells and acts on alpha cells, while alpha-factor is secreted by alpha cells and acts on a cells. Confirming preliminary studies, we demonstrate here that cultures of a cells contain higher than constitutive levels of a-factor activity when grown with alpha cells or alpha-factor. This induction of a-factor may result from increased synthesis or increased secretion of a-factor, as opposed to modification or stabilization of preexisting a-factor, as part of the a cell response to alpha-factor, as an a ste2 mutant (which cannot respond to alpha-factor) is not induced by alpha-factor. In mixed cultures inoculated with equal numbers of a cells and alpha cells, a cells predominate by stationary phase. Thus, a series of sequential interactions between a and alpha cells may be involved in establishing optimal hormone concentrations and cell ratios for conjugation.     

Probabilistic reasoning by neurons

Our brains allow us to reason about alternatives and to make choices that are likely to pay off. Often there is no one correct answer, but instead one that is favoured simply because it is more likely to lead to reward. A variety of probabilistic classification tasks probe the covert strategies that humans use to decide among alternatives based on evidence that bears only probabilistically on outcome. Here we show that rhesus monkeys can also achieve such reasoning. We have trained two monkeys to choose between a pair of coloured targets after viewing four shapes, shown sequentially, that governed the probability that one of the targets would furnish reward. Monkeys learned to combine probabilistic information from the shape combinations. Moreover, neurons in the parietal cortex reveal the addition and subtraction of probabilistic quantities that underlie decision-making on this task.     

Structural insight into filament formation by mammalian septins

Septins are GTP-binding proteins that assemble into homo- and hetero-oligomers and filaments. Although they have key roles in various cellular processes, little is known concerning the structure of septin subunits or the organization and polarity of septin complexes. Here we present the structures of the human SEPT2 G domain and the heterotrimeric human SEPT2-SEPT6-SEPT7 complex. The structures reveal a universal bipolar polymer building block, composed of an extended G domain, which forms oligomers and filaments by conserved interactions between adjacent nucleotide-binding sites and/or the amino- and carboxy-terminal extensions. Unexpectedly, X-ray crystallography and electron microscopy showed that the predicted coiled coils are not involved in or required for complex and/or filament formation. The asymmetrical heterotrimers associate head-to-head to form a hexameric unit that is nonpolarized along the filament axis but is rotationally asymmetrical. The architecture of septin filaments differs fundamentally from that of other cytoskeletal structures.     

Plasma HIV-1-RNA Load Determination by the Ultrasensitive Protocol:A Tool Necessary for the Management in Antiretorviral Treatment

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Structure of mammalian AMPK and its regulation by ADP

The heterotrimeric AMP-activated protein kinase (AMPK) has a key role in regulating cellular energy metabolism; in response to a fall in intracellular ATP levels it activates energy-producing pathways and inhibits energy-consuming processes. AMPK has been implicated in a number of diseases related to energy metabolism including type 2 diabetes, obesity and, most recently, cancer. AMPK is converted from an inactive form to a catalytically competent form by phosphorylation of the activation loop within the kinase domain: AMP binding to the γ-regulatory domain promotes phosphorylation by the upstream kinase, protects the enzyme against dephosphorylation, as well as causing allosteric activation. Here we show that ADP binding to just one of the two exchangeable AXP (AMP/ADP/ATP) binding sites on the regulatory domain protects the enzyme from dephosphorylation, although it does not lead to allosteric activation. Our studies show that active mammalian AMPK displays significantly tighter binding to ADP than to Mg-ATP, explaining how the enzyme is regulated under physiological conditions where the concentration of Mg-ATP is higher than that of ADP and much higher than that of AMP. We have determined the crystal structure of an active AMPK complex. The structure shows how the activation loop of the kinase domain is stabilized by the regulatory domain and how the kinase linker region interacts with the regulatory nucleotide-binding site that mediates protection against dephosphorylation. From our biochemical and structural data we develop a model for how the energy status of a cell regulates AMPK activity.     

New mammalian chloride channel identified by expression cloning.

Ion channels selectively permeable to chloride ions regulate cell functions as diverse as excitability and control of cell volume. Using expression cloning techniques, a complementary DNA from an epithelial cell line has been isolated, sequenced and its putative structure examined by site-directed mutagenesis. This cDNA, encoding a 235-amino-acid protein, gave rise to a chloride-selective outward current when expressed in Xenopus oocytes. The expressed, outwardly rectifying chloride current was calcium-insensitive and was blocked by nucleotides applied to the cell surface. Mutation of a putative nucleotide-binding site resulted in loss of nucleotide block but incurred dependence on extracellular calcium concentration. The unusual sequence of this putative channel protein suggests a new class of ion channels not related to other previously cloned chloride channels.     

Direct control of paralysed muscles by cortical neurons

A potential treatment for paralysis resulting from spinal cord injury is to route control signals from the brain around the injury by artificial connections. Such signals could then control electrical stimulation of muscles, thereby restoring volitional movement to paralysed limbs. In previously separate experiments, activity of motor cortex neurons related to actual or imagined movements has been used to control computer cursors and robotic arms, and paralysed muscles have been activated by functional electrical stimulation. Here we show that Macaca nemestrina monkeys can directly control stimulation of muscles using the activity of neurons in the motor cortex, thereby restoring goal-directed movements to a transiently paralysed arm. Moreover, neurons could control functional stimulation equally well regardless of any previous association to movement, a finding that considerably expands the source of control signals for brain-machine interfaces. Monkeys learned to use these artificial connections from cortical cells to muscles to generate bidirectional wrist torques, and controlled multiple neuron-muscle pairs simultaneously. Such direct transforms from cortical activity to muscle stimulation could be implemented by autonomous electronic circuitry, creating a relatively natural neuroprosthesis. These results are the first demonstration that direct artificial connections between cortical cells and muscles can compensate for interrupted physiological pathways and restore volitional control of movement to paralysed limbs.