Biology subjects

Juarez, B.

Publications and source records attributed to Juarez, B..

6 recordsLinked to original sources

bioRxiv2026

Aquatic respiratory rates in red devil vampire crabs (Geosesarma hagen) are dependent on interactions between temperature, sex, and body size

The shift to terrestrial environments in ancestrally aquatic animals is often associated with key physiological and physical changes, including shifts in respiratory physiology and in some cases, even the evolution of completely novel respiratory structures. Examining how respiration operates across a gradient of submersion states in ancestrally aquatic terrestrial animals may shed light on how complex biological traits shift under different selective regimes. In this work, we begin exploring respiration in terrestrially-adapted land crabs that still use their gills to respire while underwater. We tested the relationship between aquatic respiratory rates, body size, and sex in red devil vampire crabs (Geosesarma hagen) at two ecologically-relevant temperatures. We found small females respire more than small males at 28{degrees}C, while large females respire more than large males at 21{degrees}C. Additionally, body size is a significant factor affecting respiratory rates of both sexes at 21{degrees}C and warmer temperatures significantly increase respiration in small crabs of both sexes. Interactions between these factors also led to emerging trends that can be explained by both physiological rules, such as reproductive investment and surface-to-volume ratios and heat transfer. We also report a temperature coefficient (Q10) of 1.52 for this species, showing an expected 52% change in respiratory and metabolic rate for every 10{degrees}C increase. This work also demonstrates the importance of understanding how and to what extent biological variables like sex and body size interact with abiotic environmental factors when measuring physiological traits in ectothermic invertebrate animals. What is already knownAs crabs colonize terrestrial environments, they undergo adaptive physical and physiological changes in their respiratory abilities. Few studies have examined these respiratory shifts in individual terrestrial crab species using modern respirometry tools and techniques and across different submersion states and biotic and abiotic factors. We quantify how temperature, body size, and sex affect aquatic respiratory rates in adult terrestrial vampire crabs. What this study addsWe found small females respire more than small males at 28{degrees}C, while large females respire more than large males at 21{degrees}C. Additionally, body size is a significant factor affecting respiratory rates of both sexes at 21{degrees}C and warmer temperatures significantly increase respiration in small crabs of both sexes. Interactions between these factors also led to emerging trends that can be explained by both physiological rules, such as reproductive investment and surface-to-volume ratios and heat transfer. We also report a temperature coefficient (Q10) of 1.52 for this species, showing an expected 52% change in respiratory and metabolic rate for every 10{degrees}C increase.

physiology↗

bioRxiv2024

Distinct dynamics and intrinsic properties in ventral tegmental area populations mediate reward association and motivation

Ventral tegmental area (VTA) dopamine neurons regulate reward-related associative learning and reward-driven motivated behaviors, but how these processes are coordinated by distinct VTA neuronal subpopulations remains unresolved. Here we examine the neural correlates of reward-related prediction-error, action, cue, and outcome encoding as well as effort exertion and reward anticipation during reward-seeking behaviors. We compare the contribution of two primarily dopaminergic and largely non-overlapping VTA subpopulations, all VTA dopamine neurons, and VTA GABAergic neurons of the mouse midbrain to these processes. The dopamine subpopulation that projects to the nucleus accumbens (NAc) core preferentially encodes prediction-error and reward-predictive cues. In contrast, the dopamine subpopulation that projects to the NAc shell preferentially encodes goal-directed actions and reflects relative reward anticipation. VTA GABA neuron activity strongly contrasts VTA dopamine population activity and preferentially encodes reward outcome and retrieval. Electrophysiology, targeted optogenetics, and whole-brain input mapping reveal heterogeneity among VTA dopamine subpopulations. Our results demonstrate that VTA subpopulations carry distinct reward-related learning and motivation signals and reveal a striking pattern of functional heterogeneity among projection-defined VTA dopamine neuron populations.

neuroscience↗

bioRxiv2023

An arginine-rich nuclear localization signal (ArgiNLS) strategy for streamlined image segmentation of single-cells

High-throughput volumetric fluorescent microscopy pipelines can spatially integrate whole-brain structure and function at the foundational level of single-cells. However, conventional fluorescent protein (FP) modifications used to discriminate single-cells possess limited efficacy or are detrimental to cellular health. Here, we introduce a synthetic and non-deleterious nuclear localization signal (NLS) tag strategy, called Arginine-rich NLS (ArgiNLS), that optimizes genetic labeling and downstream image segmentation of single-cells by restricting FP localization near-exclusively in the nucleus through a poly-arginine mechanism. A single N-terminal ArgiNLS tag provides modular nuclear restriction consistently across spectrally separate FP variants. ArgiNLS performance in vivo displays functional conservation across major cortical cell classes, and in response to both local and systemic brain wide AAV administration. Crucially, the high signal-to-noise ratio afforded by ArgiNLS enhances ML-automated segmentation of single-cells due to rapid classifier training and enrichment of labeled cell detection within 2D brain sections or 3D volumetric whole-brain image datasets, derived from both staining-amplified and native signal. This genetic strategy provides a simple and flexible basis for precise image segmentation of genetically labeled single-cells at scale and paired with behavioral procedures. Significance StatementQuantifying labeled cells in fluorescent microscopy is a fundamental aspect of modern biology. Critically, the use of short nuclear localization sequences (NLS) is a key genetic modification for discriminating single-cells labeled with fluorescent proteins (FPs). However, mainstay NLS approaches typically localize proteins to the nucleus with limited efficacy, while alternative non-NLS tag strategies can enhance efficacy at the cost of cellular health. Thus, quantitative cell counting using FP labels remains suboptimal or not compatible with health and behavior. Here, we present a novel genetic tagging strategy - named ArgiNLS - that flexibly and safely achieves FP nuclear restriction across the brain to facilitate machine learning-based segmentation of single-cells at scale, delivering a timely update to the behavioral neuroscientists toolkit.

neuroscience↗

bioRxiv2022

Netrin-1 regulates the balance of glutamatergic connectivity in the adult ventral tegmental area

The axonal guidance cue netrin-1 serves a critical role in neural circuit development by promoting growth cone motility, axonal branching, and synaptogenesis. Within the adult mouse brain, expression of the gene encoding netrin-1 (Ntn1) is highly enriched in the ventral midbrain where it is expressed in both GABAergic and dopaminergic neurons, but its function in these cell types in the adult system remains largely unknown. To address this, we performed viral-mediated, cell-type specific CRISPR-Cas9 mutagenesis of Ntn1 in the ventral tegmental area (VTA) of adult mice. Ntn1 loss-of-function in either cell type resulted in a significant reduction in excitatory postsynaptic connectivity. In dopamine neurons, reduced excitatory tone had a minimal phenotypic behavioral outcome; however, reduced glutamatergic tone on VTA GABA neurons induced behaviors associated with a hyperdopaminergic phenotype. Loss of Ntn1 function in both cell types simultaneously largely rescued the phenotype observed in the GABA-only mutagenesis. These findings demonstrate an important role for netrin-1 in maintaining excitatory connectivity in the adult midbrain and that a balance in this connectivity within two of the major cell types of the VTA is critical for the proper functioning of the mesolimbic system.

neuroscience↗

bioRxiv2021

Intrinsic regulators of the action potential waveform control dopamine release to shape behavior

Despite the widely known role of dopamine in reinforcement learning, how the patterns of dopamine release that are critical to the acquisition, performance, and extinction of conditioned responses are generated is poorly resolved. Here, we demonstrate that the coordinated actions of two ion channels, Kv4.3 and BKCa1.1, control the pattern of dopamine neuron firing and dopamine release on different time scales to regulate separate phases of reinforced behavior in mice. Inactivation of Kv4.3 in VTA dopamine neurons increases ex vivo pacemaker activity and excitability that is associated with increased in vivo ramping dynamics prior to lever press in a learned instrumental response paradigm. Loss of Kv4.3 enhances performance of the learned response and facilitates extinction. In contrast, loss of BKCa1.1 increases burst firing and phasic dopamine release that enhances learning of an instrumental response. Inactivation of BKCa1.1 enhances extinction burst lever pressing in early extinction training that is associated with increased reward prediction error signals. These data demonstrate that temporally distinct patterns of dopamine release are governed by the intrinsic regulators of the cell to shape behavior. TeaserWe show that ion channels in midbrain dopamine neurons are critical for patterning action potential firing at the cell body and governing neurotransmitter release to regulate reinforcement learning.

neuroscience↗

bioRxiv2020

CRISPR Knockdown of Kcnq3 Attenuates the M-current in NPY/AgRP Neurons

Arcuate nucleus Neuropeptide Y/Agouti-related peptide (NPY/AgRP) neurons drive ingestive behavior in response to the internal and external environment of an organism. NPY/AgRP neurons are adjacent to the median eminence, a circumventricular organ, and circulating metabolic factors and hormones communicate the energy state of the animal via these neurons by altering the excitability of NPY/AgRP neurons, which produces an appropriate change in behavior to maintain homeostasis. One example of this plasticity is seen in the M-current, a subthreshold, non-inactivating K+ current that acts to modulate excitability. Fasting decreases while estradiol increases the M-current through regulation of subunit mRNA expression of Kcnq 2, 3, & 5. KCNQ2/3 heteromers are thought to mediate the majority of the M-current. Here we used a recently developed single adeno-associated viral (AAV) vector containing a recombinase-dependent Staphylococcus aureus Cas9 (SaCas9) and a single guide RNA against Kcnq3 to selectively delete Kcnq3 in NPY/AgRP neurons to produce a loss of function in the M-current. We found that this virus was effective at knocking down Kcnq3 but not Kcnq2 expression. With the reduced KCNQ3 channel expression NPY/AgRP neurons were more depolarized, exhibited a higher input resistance, and the rheobase current needed to induce firing was significantly reduced, indicative of increased excitability. Although the resulting decrease in the M-current did not overtly alter ingestive behavior, it did significantly reduce the locomotor activity as measured in open field testing. Therefore, the SaCas9-sgKcnq3 is efficient to knock down Kcnq3 expression thereby reducing the M-current and increasing the excitability of NPY/AgRP neurons.

neuroscience↗