Biology subjects

Margolis, E.

Publications and source records attributed to Margolis, E..

4 recordsLinked to original sources

bioRxiv2025

Hyperthermic Seizure Susceptibility and Focal Decreases in Parvalbumin-Expressing Cortical Interneurons in a Mouse Model of PCDH19-Clustering Epilepsy

ObjectiveProtocadherin-19 (PCDH19)-clustering epilepsy (PCE) is a severe genetic epilepsy that manifests with early-onset cluster seizures often triggered by fever, intellectual disability, autistic features, and later neuropsychiatric risk. PCDH19 is an X-linked gene critical for brain development. PCE predominantly affects females and rare mosaic males, but not hemizygous males, likely due to cellular mosaicism arising from random X-inactivation and resultant segregation of wild-type and mutant neurons (so-called cellular interference) during development. We generated a novel PCE mouse model and explored neuronal segregation, seizure susceptibility and cortical interneuron distributions. MethodsFemale Pcdh19+/- mice were crossed with X-GFP males to visualize random X-inactivation patterns. Seizure susceptibility was assessed in juvenile mice using hyperthermia and flurothyl exposure. Behavioral testing evaluated cognitive domains. Interneuron distribution in hippocampus and cortex was examined histologically by immunolabeling and crosses with parvalbumin reporter mice. ResultsJuvenile Pcdh19+/- females lacked spontaneous seizures but displayed lower seizure thresholds and more severe seizures during hyperthermia. Seizure susceptibility did not differ from controls after flurothyl exposure. Pcdh19+/- females also exhibited segregation of GFP+ cells in the cortex, hippocampal CA1 region and medial ganglionic eminence, with a marked reduction of parvalbumin-positive interneurons in the CA1 hippocampal region. Although parvalbumin interneuron density was unchanged in the Pcdh19+/- female cortex overall, localized decreases arose in GFP- (Pcdh19 knockout) cortical stripes. InterpretationJuvenile PCE mice exhibit seizure susceptibility to hyperthermia and disrupted the distribution of parvalbumin-expressing interneurons in the hippocampus and cortex. These findings suggest focal parvalbumin interneuron alterations may contribute to PCE pathophysiology.

neuroscience↗

bioRxiv2024

Chronic hyperactivation of midbrain dopamine neurons causes preferential dopamine neuron degeneration

Parkinsons disease (PD) is characterized by the death of substantia nigra (SNc) dopamine (DA) neurons, but the pathophysiological mechanisms that precede and drive their death remain unknown. The activity of DA neurons is likely altered in PD, but we understand little about if or how chronic changes in activity may contribute to degeneration. To address this question, we developed a chemogenetic (DREADD) mouse model to chronically increase DA neuron activity, and confirmed this increase using ex vivo electrophysiology. Chronic hyperactivation of DA neurons resulted in prolonged increases in locomotor activity during the light cycle and decreases during the dark cycle, consistent with chronic changes in DA release and circadian disturbances. We also observed early, preferential degeneration of SNc projections, recapitulating the PD hallmarks of selective vulnerability of SNc axons and the comparative resilience of ventral tegmental area axons. This was followed by eventual loss of midbrain DA neurons. Continuous DREADD activation resulted in a sustained increase in baseline calcium levels, supporting a role for increased calcium in the neurodegeneration process. Finally, spatial transcriptomics from DREADD mice examining midbrain DA neurons and striatal targets, and cross-validation with human patient samples, provided insights into potential mechanisms of hyperactivity-induced toxicity and PD. Our results thus reveal the preferential vulnerability of SNc DA neurons to increased neural activity, and support a potential role for increased neural activity in driving degeneration in PD.

neuroscience↗

bioRxiv2020

Respiratory bacteria stabilize and promote airborne transmission of influenza A virus

Influenza A virus (IAV) is a major pathogen of the human respiratory tract where the virus co-exists and interacts with bacterial populations comprising the respiratory microbiome. Synergies between IAV and respiratory bacterial pathogens promote enhanced inflammation and disease burden that exacerbate morbidity and mortality. We demonstrate that direct interactions between IAV and encapsulated bacteria commonly found in the respiratory tract promote environmental stability and infectivity of IAV. Antibiotic-mediated depletion of the respiratory bacterial flora abrogated IAV transmission in ferret models, indicating that these viral-bacterial interactions are operative for airborne transmission of IAV. Restoring IAV airborne transmission in antibiotic treated ferrets by co-infection with Streptococcus pneumoniae confirmed a role for specific members of the bacterial respiratory community in promoting IAV transmission. These results implicate a role for the bacterial respiratory flora in promoting airborne transmission of IAV.

microbiology↗

bioRxiv2017

Instantiation of incentive value and movement invigoration by distinct midbrain dopamine circuits

Environmental cues, through Pavlovian learning, become conditioned stimuli that guide animals towards the acquisition of \"rewards\" (i.e., food) that are necessary for survival. Here, we test the fundamental role of midbrain dopamine neurons in conferring predictive or motivational properties to cues, independent of external rewards. We demonstrate that phasic optogenetic excitation of dopamine neurons throughout the midbrain, when presented in temporal association with discrete sensory cues, is sufficient to instantiate those cues as conditioned stimuli that subsequently both evoke dopamine neuron activity on their own, and elicit cue-locked conditioned behaviors. Critically, we identify highly parcellated behavioral functions for dopamine neuron subpopulations projecting to discrete regions of striatum, revealing dissociable mesostriatal systems for the generation of incentive value and movement invigoration. These results show that dopamine neurons orchestrate Pavlovian conditioning via functionally heterogeneous, circuit-specific motivational signals to shape cue-controlled behavior.

neuroscience↗