Unraveling neuronal and metabolic alterations in neurofibromatosis type 1.

Neurofibromatosis type 1 (OMIM 162200) affects ~ 1 in 3,000 individuals worldwide and is one of the most common monogenetic neurogenetic disorders that impacts brain function. The disorder affects various organ systems, including the central nervous system, resulting in a spectrum of clinical manifestations. Significant progress has been made in understanding the disorder's pathophysiology, yet gaps persist in understanding how the complex signaling and systemic interactions affect the disorder.

Modeling neurodegenerative and neurodevelopmental disorders in the mushroom body.

The common fruit fly provides a powerful platform to investigate the genetic, molecular, cellular, and neural circuit mechanisms of behavior. Research in this model system has shed light on multiple aspects of brain physiology and behavior, from fundamental neuronal function to complex behaviors. A major anatomical region that modulates complex behaviors is the mushroom body (MB).

Neurofibromin 1 mediates sleep depth in Drosophila.

Neural regulation of sleep and metabolic homeostasis are critical in many aspects of human health. Despite extensive epidemiological evidence linking sleep dysregulation with obesity, diabetes, and metabolic syndrome, little is known about the neural and molecular basis for the integration of sleep and metabolic function. The RAS GTPase-activating gene Neurofibromin (Nf1) has been implicated in the regulation of sleep and metabolic rate, raising the possibility that it serves to integrate these processes, but the effects on sleep consolidation and physiology remain poorly understood.

Functional Imaging of Learning-Induced Plasticity in the Central Nervous System with Genetically Encoded Reporters in .

Learning and memory allow animals to adjust their behavior based on the predictive value of their past experiences. Memories often exist in complex representations, spread across numerous cells and synapses in the brain. Studying relatively simple forms of memory provides insights into the fundamental processes that underlie multiple forms of memory.

Imaging Olfactory Learning-Induced Plasticity in Vivo in the Brain.

In vivo imaging of brain activity in allows the dissection of numerous types of biologically important neuronal events. A common paradigm involves imaging neuronal Ca transients, often in response to sensory stimuli. These Ca transients correlate with neuronal spiking activity, which generates voltage-sensitive Ca influx.

Ex Vivo Brain Imaging in .

Analysis of neuronal circuit function in can be facilitated with an ex vivo imaging preparation. In this approach, the brain is isolated but intact, preserving neuronal connectivity and function. The preparation has several advantages, including stability, accessibility for pharmacological manipulations, and the ability to image over several hours.

Associative learning drives longitudinally graded presynaptic plasticity of neurotransmitter release along axonal compartments.

Anatomical and physiological compartmentalization of neurons is a mechanism to increase the computational capacity of a circuit, and a major question is what role axonal compartmentalization plays. Axonal compartmentalization may enable localized, presynaptic plasticity to alter neuronal output in a flexible, experience-dependent manner. Here, we show that olfactory learning generates compartmentalized, bidirectional plasticity of acetylcholine release that varies across the longitudinal compartments of mushroom body (MB) axons.

Dopamine, sleep, and neuronal excitability modulate amyloid-β-mediated forgetting in Drosophila.

Alzheimer disease (AD) is one of the main causes of age-related dementia and neurodegeneration. However, the onset of the disease and the mechanisms causing cognitive defects are not well understood. Aggregation of amyloidogenic peptides is a pathological hallmark of AD and is assumed to be a central component of the molecular disease pathways.

Neurofibromin regulates metabolic rate via neuronal mechanisms in Drosophila.

Neurofibromatosis type 1 is a chronic multisystemic genetic disorder that results from loss of function in the neurofibromin protein. Neurofibromin may regulate metabolism, though the underlying mechanisms remain largely unknown. Here we show that neurofibromin regulates metabolic homeostasis in Drosophila via a discrete neuronal circuit.

Developmental loss of neurofibromin across distributed neuronal circuits drives excessive grooming in Drosophila.

Neurofibromatosis type 1 is a monogenetic disorder that predisposes individuals to tumor formation and cognitive and behavioral symptoms. The neuronal circuitry and developmental events underlying these neurological symptoms are unknown. To better understand how mutations of the underlying gene (NF1) drive behavioral alterations, we have examined grooming in the Drosophila neurofibromatosis 1 model.

Cellular and circuit mechanisms of olfactory associative learning in .

Recent years have witnessed significant progress in understanding how memories are encoded, from the molecular to the cellular and the circuit/systems levels. With a good compromise between brain complexity and behavioral sophistication, the fruit fly is one of the preeminent animal models of learning and memory. Here we review how memories are encoded in , with a focus on short-term memory and an eye toward future directions.

Independent Contributions of Discrete Dopaminergic Circuits to Cellular Plasticity, Memory Strength, and Valence in Drosophila.

Dopaminergic neurons play a key role in encoding associative memories, but little is known about how these circuits modulate memory strength. Here we report that different sets of dopaminergic neurons projecting to the Drosophila mushroom body (MB) differentially regulate valence and memory strength. PPL2 neurons increase odor-evoked calcium responses to a paired odor in the MB and enhance behavioral memory strength when activated during olfactory classical conditioning.

The Excitatory, the Inhibitory, and the Modulatory: Mapping Chemical Neurotransmission in the Brain.

In this issue of Neuron, Deng et al. (2019) report the generation of a new set of tools to manipulate the entire set of neurotransmitters, neuromodulators, neuropeptides, and their receptors-the "chemoconnectome"-in Drosophila.

Elongator complex is required for long-term olfactory memory formation in .

The evolutionarily conserved Elongator Complex associates with RNA polymerase II for transcriptional elongation. Elp3 is the catalytic subunit, contains histone acetyltransferase activity, and is associated with neurodegeneration in humans. Elp1 is a scaffolding subunit and when mutated causes familial dysautonomia.

Cyclic AMP-dependent plasticity underlies rapid changes in odor coding associated with reward learning.

Learning and memory rely on dopamine and downstream cAMP-dependent plasticity across diverse organisms. Despite the central role of cAMP signaling, it is not known how cAMP-dependent plasticity drives coherent changes in neuronal physiology that encode the memory trace, or engram. In , the mushroom body (MB) is critically involved in olfactory classical conditioning, and cAMP signaling molecules are necessary and sufficient for normal memory in intrinsic MB neurons.

Postprandial sleep mechanics in .

Food consumption is thought to induce sleepiness. However, little is known about how postprandial sleep is regulated. Here, we simultaneously measured sleep and food intake of individual flies and found a transient rise in sleep following meals.

Neurofibromin Loss of Function Drives Excessive Grooming in Drosophila.

Neurofibromatosis I is a common genetic disorder that results in tumor formation, and predisposes individuals to a range of cognitive/behavioral symptoms, including deficits in attention, visuospatial skills, learning, language development, and sleep, and autism spectrum disorder-like traits. The nf1-encoded neurofibromin protein (Nf1) exhibits high conservation, from the common fruit fly, Drosophila melanogaster, to humans. Drosophila provides a powerful platform to investigate the signaling cascades upstream and downstream of Nf1, and the fly model exhibits similar behavioral phenotypes to mammalian models.

Neurons and behavior: ex uno, plures.

Li et al. demonstrate that a single interneuron can regulate analog- and digital-like behaviors guided by two different postsynaptic neurons. Releasing a single neurotransmitter onto downstream neurons that express receptors with distinct biophysical properties enables a small set of neurons to direct a range of functional responses.

Dopaminergic modulation of cAMP drives nonlinear plasticity across the Drosophila mushroom body lobes.

Background: Activity of dopaminergic neurons is necessary and sufficient to evoke learning-related plasticity in neuronal networks that modulate learning. During olfactory classical conditioning, large subsets of dopaminergic neurons are activated, releasing dopamine across broad sets of postsynaptic neurons. It is unclear how such diffuse dopamine release generates the highly localized patterns of plasticity required for memory formation.

Dopaminergic neurons encode a distributed, asymmetric representation of temperature in Drosophila.

Dopaminergic circuits modulate a wide variety of innate and learned behaviors in animals, including olfactory associative learning, arousal, and temperature-preference behavior. It is not known whether distinct or overlapping sets of dopaminergic neurons modulate these behaviors. Here, I have functionally characterized the dopaminergic circuits innervating the Drosophila mushroom body with in vivo calcium imaging and conditional silencing of genetically defined subsets of neurons.

Dynamics of learning-related cAMP signaling and stimulus integration in the Drosophila olfactory pathway.

Functional imaging with genetically encoded calcium and cAMP reporters was used to examine the signal integration underlying learning in Drosophila. Dopamine and octopamine modulated intracellular cAMP in spatially distinct patterns in mushroom body neurons. Pairing of neuronal depolarization with subsequent dopamine application revealed a synergistic increase in cAMP in the mushroom body lobes, which was dependent on the rutabaga adenylyl cyclase.

Cyclic AMP imaging sheds light on PDF signaling in circadian clock neurons.

In Drosophila, the neuropeptide PDF is required for circadian rhythmicity, but it is unclear where PDF acts. In this issue of Neuron, Shafer et al. use a novel bioimaging methodology to demonstrate that PDF elevates cAMP in nearly all clock neurons.