In vivo mapping of a GPCR interactome using knockin mice.

With over 30% of current medications targeting this family of proteins, G-protein-coupled receptors (GPCRs) remain invaluable therapeutic targets. However, due to their unique physicochemical properties, their low abundance, and the lack of highly specific antibodies, GPCRs are still challenging to study in vivo. To overcome these limitations, we combined here transgenic mouse models and proteomic analyses in order to resolve the interactome of the δ-opioid receptor (DOPr) in its native in vivo environment.

α2* Nicotinic acetylcholine receptors influence hippocampus-dependent learning and memory in adolescent mice.

The absence of α2* nicotinic acetylcholine receptors (nAChRs) in oriens lacunosum moleculare (OLM) GABAergic interneurons ablate the facilitation of nicotine-induced hippocampal CA1 long-term potentiation and impair memory. The current study delineated whether genetic mutations of α2* nAChRs ( and ) influence hippocampus-dependent learning and memory and CA1 synaptic plasticity. We substituted a serine for a leucine (L9'S) in the α2 subunit (encoded by the gene) to make a hypersensitive nAChR.

Targeted Deletion of Vesicular GABA Transporter from Retinal Horizontal Cells Eliminates Feedback Modulation of Photoreceptor Calcium Channels.

The cellular mechanisms underlying feedback signaling from horizontal cells to photoreceptors, which are important for the formation of receptive field surrounds of early visual neurons, remain unsettled. Mammalian horizontal cells express a complement of synaptic proteins that are necessary and sufficient for calcium-dependent exocytosis of inhibitory neurotransmitters at their contacts with photoreceptor terminals, suggesting that they are capable of releasing GABA via vesicular release. To test whether horizontal cell vesicular release is involved in feedback signaling, we perturbed inhibitory neurotransmission in these cells by targeted deletion of the vesicular GABA transporter (VGAT), the protein responsible for the uptake of inhibitory transmitter by synaptic vesicles.

Targeted deletion of the mouse α2 nicotinic acetylcholine receptor subunit gene (Chrna2) potentiates nicotine-modulated behaviors.

Baseline and nicotine-modulated behaviors were assessed in mice harboring a null mutant allele of the nicotinic acetylcholine receptor (nAChR) subunit gene α2 (Chrna2). Homozygous Chrna2(-/-) mice are viable, show expected sex and Mendelian genotype ratios, and exhibit no gross neuroanatomical abnormalities. A broad range of behavioral tests designed to assess genotype-dependent effects on anxiety (elevated plus maze and light/dark box), motor coordination (narrow bean traverse and gait), and locomotor activity revealed no significant differences between mutant mice and age-matched wild-type littermates.

Pharmacological and immunochemical characterization of alpha2* nicotinic acetylcholine receptors (nAChRs) in mouse brain.

Aim: alpha2 nAChR subunit mRNA expression in mice is most intense in the olfactory bulbs and interpeduncular nucleus. We aimed to investigate the properties of alpha2* nAChRs in these mouse brain regions.

Methods: alpha2 nAChR subunit-null mutant mice were engineered.

Nicotinic receptors in the habenulo-interpeduncular system are necessary for nicotine withdrawal in mice.

In humans, tobacco withdrawal produces symptoms that contribute to the difficulty associated with smoking cessation. Nicotine withdrawal symptoms can also be observed in rodents. A major standing question is which nicotinic receptor subtypes and which areas of the brain are necessary for nicotine withdrawal to occur.

A point mutation in the hair cell nicotinic cholinergic receptor prolongs cochlear inhibition and enhances noise protection.

The transduction of sound in the auditory periphery, the cochlea, is inhibited by efferent cholinergic neurons projecting from the brainstem and synapsing directly on mechanosensory hair cells. One fundamental question in auditory neuroscience is what role(s) this feedback plays in our ability to hear. In the present study, we have engineered a genetically modified mouse model in which the magnitude and duration of efferent cholinergic effects are increased, and we assess the consequences of this manipulation on cochlear function.

Properties of mutated murine alpha4beta2 nicotinic receptors linked to partial epilepsy.

We characterized, by electrophysiological methods, two biophysical properties of murine recombinant alpha4beta2 nicotinic acetylcholine receptors (nAChR) bearing a mutation (alpha4:+L264alpha4:beta2 or alpha4:S252Falpha4:beta2) linked to autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). Sensitivity to acetylcholine (ACh) was increased by the S252F substitution expressed in heterozygosis (alpha4:S252Falpha4:beta2) but was markedly reduced when this mutation was expressed in homozygosis (S252Falpha4:beta2). ACh sensitivity was not altered by the +L264 insertion.

The alpha10 nicotinic acetylcholine receptor subunit is required for normal synaptic function and integrity of the olivocochlear system.

Although homomeric channels assembled from the alpha9 nicotinic acetylcholine receptor (nAChR) subunit are functional in vitro, electrophysiological, anatomical, and molecular data suggest that native cholinergic olivocochlear function is mediated via heteromeric nAChRs composed of both alpha9 and alpha10 subunits. To gain insight into alpha10 subunit function in vivo, we examined olivo cochlear innervation and function in alpha10 null-mutant mice. Electrophysiological recordings from postnatal (P) days P8-9 inner hair cells revealed ACh-gated currents in alpha10(+/+) and alpha10(+/-) mice, with no detectable responses to ACh in alpha10(-/-) mice.

Nicotine gates long-term potentiation in the hippocampal CA1 region via the activation of alpha2* nicotinic ACh receptors.

Hippocampal CA1 pyramidal cells receive two major excitatory synaptic inputs via the Schaffer collateral (SC) and temporoammonic (TA) pathways. Nicotine promotes induction of long-term potentiation (LTP) in the SC path; however, it is not known whether the modulatory effect of nicotine on LTP induction is pathway-specific. Here we show that nicotine suppresses LTP induction in the TA path.

Seizures and enhanced cortical GABAergic inhibition in two mouse models of human autosomal dominant nocturnal frontal lobe epilepsy.

Selected mutations in the human alpha4 or beta2 neuronal nicotinic acetylcholine receptor subunit genes cosegregate with a partial epilepsy syndrome known as autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). To examine possible mechanisms underlying this inherited epilepsy, we engineered two ADNFLE mutations (Chrna4(S252F) and Chrna4(+L264)) in mice. Heterozygous ADNFLE mutant mice show persistent, abnormal cortical electroencephalograms with prominent delta and theta frequencies, exhibit frequent spontaneous seizures, and show an increased sensitivity to the proconvulsant action of nicotine.

The divergent DSL ligand Dll3 does not activate Notch signaling but cell autonomously attenuates signaling induced by other DSL ligands.

Mutations in the DSL (Delta, Serrate, Lag2) Notch (N) ligand Delta-like (Dll) 3 cause skeletal abnormalities in spondylocostal dysostosis, which is consistent with a critical role for N signaling during somitogenesis. Understanding how Dll3 functions is complicated by reports that DSL ligands both activate and inhibit N signaling. In contrast to other DSL ligands, we show that Dll3 does not activate N signaling in multiple assays.

The beta3 nicotinic receptor subunit: a component of alpha-conotoxin MII-binding nicotinic acetylcholine receptors that modulate dopamine release and related behaviors.

Nigrostriatal dopaminergic neurons express many nicotinic acetylcholine receptor (nAChR) subunits capable of forming multiple nAChR subtypes. These subtypes are expressed differentially along the neuron and presumably mediate diverse responses. beta3 subunit mRNA has restricted expression but is abundant in the substantia nigra and ventral tegmental areas.

Cloning of the zebra finch androgen synthetic enzyme CYP17: a study of its neural expression throughout posthatch development.

Male zebra finches develop a robust neural song system that supports singing, but females have a minimal song circuit and do not sing. Estrogens masculinize the song circuit and are especially potent during the first 3 weeks of posthatch development. The gonads do not seem to supply the masculinizing steroids, implying that another tissue synthesizes steroids.

CADASIL Notch3 mutant proteins localize to the cell surface and bind ligand.

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a vascular dementia arising from abnormal arteriolar vascular smooth muscle cells. CADASIL results from mutations in Notch3 that alter the number of cysteine residues in the extracellular epidermal growth factor-like repeats, important for ligand binding. It is not known whether CADASIL mutations lead to loss or gain of Notch3 receptor function.