Faculty Bibliography

INTRODUCTION/BACKGROUND:The long-standing cholinergic hypothesis posits that cholinergic signaling is uniformly deficient in Alzheimer's disease (AD) and Down syndrome (DS). We tested the hypothesis that this deficiency occurs primarily late in disease, while early stages involve excessive cholinergic signaling, with distinct implications for memory. METHODS:Tg2576 (AD model; n = 38), Ts65Dn (DS model; n = 14), and wild-type (WT; n = 17) mice at young (3 to 4 months) and old (>14 months) ages received treatments to reduce cholinergic signaling (medial septum chemogenetic inhibition, muscarinic antagonist scopolamine) or enhance it (acetylcholinesterase inhibitor donepezil). Memory assessments used novel object recognition. RESULTS:Anticholinergic manipulations restored memory in young Tg2576 and Ts65Dn mice but impaired age-matched WT mice. Conversely, donepezil improved the memory of old Tg2576, Ts65Dn, and WT but not young Tg2576 and Ts65Dn animals. DISCUSSION/CONCLUSIONS:These findings refine and challenge the cholinergic hypothesis, revealing for the first time a functional shift from cholinergic hyperactivity driving early cognitive impairment to late-stage degeneration requiring enhancement.

PURPOSE/OBJECTIVE:Establish the minimally clinically important difference (MCID) for the Orthostatic Hypotension Questionnaire (OHQ). BACKGROUND:Neurogenic orthostatic hypotension (nOH) causes disabling symptoms that impair daily function and quality of life. The OHQ is a validated patient-reported outcome with a symptom assessment (OHSA) and daily activity scale (OHDAS), widely used in clinical trials, despite the MCID being unestablished. METHODS:We analyzed data from two phase 3, randomized placebo-controlled trials (SEQUOIA and REDWOOD), evaluating ampreloxetine for symptomatic nOH in patients with Parkinson disease, multiple system atrophy, and pure autonomic failure. Using anchor-based and distribution-based methods, we calculated the MCID for the total OHQ score, OHSA and OHDAS composite subscales, and for the single dizziness/lightheadedness question (OHSA1). RESULTS:The analysis included 184 subjects from SEQUOIA and 128 from REDWOOD. The total OHQ MCID for improvement was a reduction of 0.9-1.2 points and for worsening was an increase of 0.7-1.1 points. The MCID for the OHSA composite ranged from a reduction of 0.9-1.3 points for improvement and an increase of 0.7-1.1 points for worsening. For the single-item OHSA1, the MCID was a reduction of 2.0-3.0 points for improvement and an increase of 1.0 point for worsening. Owing to poor correlation with the symptom-based anchors, a reliable MCID for the OHDAS component was not established. CONCLUSIONS:These MCID thresholds for the OHQ, OHSA and OHSA item 1 alone, enhance the interpretability of scores and support their use in evaluating clinical benefit.

Xenotransplantation of genetically-modified pig kidneys offers a solution to the scarcity of organs for end-stage renal disease patients.¹ We performed a 61-day alpha-Gal knock-out pig kidney and thymic autograft transplant into a nephrectomized brain-dead human using clinically approved immunosuppression, without CD40 blockade or additional genetic modification. Hemodynamic and electrolyte stability and dialysis independence were achieved. Post-operative day (POD) 10 biopsies revealed glomerular IgM and IgA deposition, activation of early complement components and mesangiolysis with stable renal function without proteinuria, a phenotype not seen in allotransplantation. On POD 33, an abrupt increase in serum creatinine was associated with antibody-mediated rejection and increased donor-specific IgG. Plasma exchange, C3/C3b inhibition and rabbit anti-thymocyte globulin (rATG), completely reversed xenograft rejection. Pre-existing donor-reactive T cell clones expanded progressively in the circulation post-transplant, acquired an effector transcriptional profile and were detected in the POD 33 rejecting xenograft prior to rATG treatment. This study provides the first long-term physiologic, immunologic, and infectious disease monitoring of a pig-to-human kidney xenotransplant and indicates that pre-existing xenoreactive T cells and induced antibodies to unknown epitope(s) present a major challenge, despite significant immunosuppression. It also demonstrates that a minimally gene-edited pig kidney can support long-term life-sustaining physiologic functions in a human.

INTRODUCTION/BACKGROUND:Choroid plexus (ChP) enlargement is a neuroimaging biomarker of neuroinflammation and neurodegeneration. However, evidence of ChP structural and perfusion alterations in long coronavirus disease (COVID) and their clinical relevance remains limited. METHODS:This study included 86 long COVID, 67 recovered COVID, and 26 COVID-negative healthy controls (HCs). ChP volume and cerebral blood flow (CBF) were quantified, and their associations with Alzheimer's disease (AD) symptoms and plasma biomarkers were examined. RESULTS:Both patient groups showed higher ChP volume and lower CBF than HC. Relative to recovered COVID, long COVID patients had a larger ChP volume, but no significant difference in CBF. ChP volume correlated positively with glial fibrillary acidic protein (r = 0.35) and phosphorylated tau217 (p-tau217; r = 0.54), while CBF correlated negatively with p-tau217 (r = -0.56). Both ChP volume and CBF were associated with cognitive decline measured with Mini-Mental State Examination and Clinical Dementia Rating. DISCUSSION/CONCLUSIONS:These findings suggest that ChP differences in long COVID are associated with AD-related cognitive decline and increased plasma biomarkers. HIGHLIGHTS/CONCLUSIONS:Long coronavirus disease (COVID) patients show choroid plexus (ChP) enlargement and reduced cerebral blood flow. ChP alterations are associated with Alzheimer's disease (AD)-related symptoms and plasma biomarker changes. ChP alterations on magnetic resonance imaging may serve as imaging markers for tracking neurological symptoms and AD-related pathology in post-COVID patients.

Astrocytes differentiate and mature during postnatal development, but the molecular mechanisms linking their maturation to neuronal function remain unclear. We investigated the role of Wnt/β-catenin signaling and its effector, the transcription factor TCF7L2, in postnatal astrocytes using single-nucleus RNA sequencing, imaging, morphometric analysis, microdialysis, and electrophysiology in Tcf7l2 conditional knockout (cKO) mice. Loss of Tcf7l2 caused widespread transcriptional dysregulation in astrocytes, particularly in genes related to amino acid and ion transport, as well as membrane potential regulation. These mice showed disrupted amino acid homeostasis, astrocyte swelling, and impaired extracellular potassium clearance in the somatosensory cortex. These astrocytic changes were accompanied by altered gene expression in cortical pyramidal neurons, reduced excitability, and a hyperpolarized resting membrane potential. Our results suggest that astrocytic TCF7L2 is crucial in coordinating ion and amino acid transport in adulthood, thereby contributing to maintaining extracellular homeostasis and supporting neuronal function. This study identifies TCF7L2 as a key regulator of astrocyte-mediated neurophysiological support and underscores the importance of its role in astrocyte maturation during postnatal development.

The piriform cortex (PCx), commonly considered to be the primary olfactory sensory cortex, differs from other mammalian sensory cortices by not displaying a stimulus-specific spatial organization but rather displaying widely distributed odor-evoked activity. However, there is evidence of a PCx spatial organization based on output neuron targeting. Here, we performed double-labeled retrograde tracing to reveal neuronal populations of PCx output neurons that project to two regions affiliated with different behavioral significance, the basolateral amygdala (BLA) and lateral orbitofrontal (LO) cortex networks. We found that PCx neurons projecting to BLA and LO are distinct in spatial distribution with minimal overlap, supporting the hypothesis that while odor input is distributed randomly across the PCx, PCx output neurons are organized into target-specific neuronal populations that potentially serve as functional units for odor encoding and odor-guided behavior.

Speech production entails several processing steps that encode linguistic and articulatory structure, but whether these computations correspond to spatiotemporally discrete patterns of neural activity is unclear. To address this issue, we use electrocorticography to directly measure the brains of neurosurgical participants performing an interactive speech paradigm. We observe a broad range of cortical modulation profiles, and subsequent clustering analyses establish that responses comprised distinct classes associated with sensory perception, planning, motor execution, and task-related suppression. These activity classes are also localized to separate neural substrates, indicating their status as specialized networks. We then parse dynamics in the planning and motor networks using unsupervised dimensionality reduction, which reveals subnetworks that are sequentially active throughout preparation and articulation. These results therefore support and extend a localizationist model of speech production where cortical activity "flows" within and across discrete pathways during language use.

Prior expectation powerfully shapes perception, yet its effects have been notoriously difficult to characterize due to the confounding influence of attention. In this study, we systematically investigated expectation's influence on conscious visual object recognition while carefully disentangling it from attentional effects. Across three experiments, we observed that expectation's effect varied markedly depending on the experimental context. When expectation was manipulated in isolation, it enhanced recognition sensitivity, mirroring the effects of attention. However, when expectation and attention were orthogonally manipulated, a surprising interaction effect emerged whereby observers were less likely to report recognition of an expected stimulus in the unattended condition-an effect attributed to swap errors. Finally, a stronger expectation cue in both space and time reduced swap errors and increased the likelihood of observers reporting seeing the expected stimuli. These findings reveal a remarkable degree of flexibility and context dependence in expectation's influence on perception and shed new light on how attention and expectation jointly shape conscious object recognition.

Organisms evolve behavioral and morphological traits to adapt to their ecological niches, yet the genetic basis of adaptation remains largely unknown. Drosophila suzukii has evolved a distinctive oviposition preference for ripe fruit, unlike most Drosophila species such as D. melanogaster, which prefer overripe fruit. Carbon dioxide (CO2), a metabolic volatile that increases as fruit ripens and decays, may act as a critical ecological cue shaping these preferences. Here, we focus on D. suzukii and its sister species D. subpulchrella, which shows an intermediate preference, to investigate the genetic basis of CO2 responses. We report a previously unrecognized shift in CO2-guided oviposition: D. suzukii and D. subpulchrella readily lay eggs on CO2-enriched substrates, unlike the strong aversion displayed by D. melanogaster. Electrophysiological recordings revealed a species-specific sensory tuning, characterized by an early spike in CO2-evoked neuronal firing in D. suzukii and D. subpulchrella-a temporal response feature absent in D. melanogaster. To dissect the genetic basis of this shift, we generated transgenic D. melanogaster expressing either the D. suzukii Gr63a coding sequence or the D. subpulchrella Gr63a cis-regulatory element. Remarkably, both manipulations reproduced the early-onset firing pattern of CO2 sensitivity, demonstrating that either receptor function or expression can independently drive this sensitivity adaptation. Our findings reveal that evolution can shape ecological adaptation through distinct genetic mechanisms, leading to convergent physiological traits among closely related species.

Developing populations of connected neurons often share spatial and/or temporal features that anticipate their assembly. A unifying spatiotemporal motif might link sensory, central, and motor populations that comprise an entire circuit. In the sensorimotor reflex circuit that stabilizes vertebrate gaze, central and motor partners are paired in time (birthdate) and space (dorso-ventral). To determine if birthdate and/or dorso-ventral organization could align the entire circuit, we measured the spatial and temporal development of the sensory circuit node: the vestibular ganglion neurons. We discovered that progressive dorsal-to-ventral organization closely predicts vestibular ganglion development, with additional organization along its functional (rostrocaudal) axis. With an acute optical lesion and calcium imaging paradigm, we found that this common temporal axis anticipated functional sensory-to-central partner matching. We propose a "first-come, first-served" model in which birthdate organizes and assembles the sensory, central, and motor populations that comprise the gaze stabilization circuit, a general strategy for poly-synaptic circuit assembly across embryonically-diverse neural populations.