Biology subjects

Blum, I. D.

Publications and source records attributed to Blum, I. D..

4 recordsLinked to original sources

bioRxiv2023

Behavioral and transcriptomic changes following brain-specific loss of noradrenergic transmission.

Noradrenaline (NE) plays an integral role in shaping behavioral outcomes including anxiety/depression, fear, learning and memory, attention and shifting behavior, sleep-wake state, pain, and addiction. However, it is unclear whether dysregulation of NE release is a cause or a consequence of maladaptive orientations of these behaviors, many of which associated with psychiatric disorders. To address this question, we used a unique genetic model in which the brain-specific Vesicular Monoamine Transporter-2 (VMAT2) gene expression was removed in NE-positive neurons disabling NE release in the entire brain. We engineered VMAT2 gene splicing and NE depletion by crossing floxed VMAT2 mice with mice expressing the Cre-recombinase under the DBH gene promotor. In this study, we performed a comprehensive behavioral and transcriptomic characterization of the VMAT2DBHcre KO mice to evaluate the role of central NE in behavioral modulations. We demonstrated that NE depletion induces anxiolytic and antidepressant-like effects, improves contextual fear memory, alters shifting behavior, decreases the locomotor response to amphetamine, and induces deeper sleep during the non-rapid eye movement (NREM) phase. In contrast, NE depletion did not affect spatial learning and memory, working memory, response to cocaine, and the architecture of the sleep-wake cycle. Finally, we used this model to identify genes that could be up- or down-regulated in the absence of NE release. We found an up-regulation of the Synaptic Vesicle Glycoprotein 2c (SV2c) gene expression in several brain regions, including the locus coeruleus (LC), and were able to validate this up-regulation as a marker of vulnerability to chronic social defeat.

neuroscience↗

bioRxiv2020

Astroglial Calcium Signaling Encodes Sleep Need in Drosophila

Sleep is under homeostatic control, whereby increasing wakefulness generates sleep need and triggers sleep drive. However, the molecular and cellular pathways by which sleep need is encoded are poorly understood. In addition, the mechanisms underlying both how and when sleep need is transformed to sleep drive are unknown. Here, using ex vivo and in vivo imaging, we show in Drosophila that astroglial Ca2+ signaling increases with sleep need. We demonstrate that this signaling is dependent on a specific L-type Ca2+ channel and is required for homeostatic sleep rebound. Thermogenetically increasing Ca2+ in astrocytes induces persistent sleep behavior, and we exploit this phenotype to conduct a genetic screen for genes required for the homeostatic regulation of sleep. From this large-scale screen, we identify TyrRII, a monoaminergic receptor required in astrocytes for sleep homeostasis. TyrRII levels rise following sleep deprivation in a Ca2+-dependent manner, promoting further increases in astrocytic Ca2+ and resulting in a positive-feedback loop. These data suggest that TyrRII acts as a gate to enable the transformation of sleep need to sleep drive at the appropriate time. Moreover, our findings suggest that astrocytes then transmit this sleep need to the R5 sleep drive circuit, by upregulation and release of the interleukin-1 analog Spatzle. These findings define astroglial Ca2+ signaling mechanisms encoding sleep need and reveal dynamic properties of the sleep homeostatic control system.

neuroscience↗

bioRxiv2020

A Clock-Driven Neural Network Critical for Arousal

The daily cycling of sleep and arousal states is among the most prominent biological rhythms under circadian control. While much is known about the core circadian clock1,2, how this clock tunes sleep and arousal remains poorly understood3. In Drosophila, we previously characterized WIDE AWAKE (WAKE), a clock-output molecule that promotes sleep at night4,5. Here, we show that the function of WAKE in regulating circadian-dependent neural excitability and arousal is conserved in mice. mWake+ cells are found in the suprachiasmatic nucleus (SCN) and dorsomedial hypothalamus (DMH). mWakeDMH neurons drive wakefulness and exhibit rhythmic spiking, with greater firing during the night vs the day. Loss of mWAKE leads to increased spiking of mWake+ SCN and DMH neurons and prominent behavioural arousal, specifically during the night. Single-cell sequencing, imaging, and patch-clamp experiments reveal that mWakeDMH neurons constitute a glutamatergic/GABAergic population that projects widely, receives neuromodulatory input, and acts on neuromodulatory neurons. Strikingly, broad chemogenetic silencing of mWake+ cells leads to profound loss of behavioural responsiveness and low amplitude, low frequency electroencephalography waveforms. These findings suggest that the genetic mechanisms regulating circadian control of sleep and arousal are conserved across >500 million years of evolution and define a clock-regulated neural network critical for arousal.

neuroscience↗

bioRxiv2019

CaMKII oxidation is a performance/disease trade-off in vertebrate evolution

Reactive oxygen species (ROS) contribute to health and disease. CaMKII is a widely expressed enzyme whose activation by oxidation of regulatory domain methionines (ox-CaMKII) contributes to cardiovascular disease, asthma, and cancer. Here we integrate comparative genomic and experimental data to show that CaMKII activation by ROS arose more than half-a-billion years ago on the vertebrate stem lineage where it constituted a bridge between ROS and increased intracellular Ca2+ release, exercise responsive gene transcription, and improved performance in skeletal muscle. These enhancements to fight-or-flight physiology were likely key in facilitating a well-evidenced shift in the behavioural ecology of our immediate chordate ancestors, and, in turn, the evolutionary success of vertebrates. Still, the ox-CaMKII innovation for augmenting performance must be considered a critical evolutionary trade-off, as it rendered us more susceptible to common and often fatal diseases linked to excessive ROS.

evolutionary biology↗