Biology subjects

Luebke, J. I.

Publications and source records attributed to Luebke, J. I..

8 recordsLinked to original sources

bioRxiv2026

Multimodal characterization of putative pan-inhibitory viral constructs in macaque monkeys

Transgenic approaches and validated viral vector toolboxes have advanced our understanding of how inhibitory neurons shape cognition and motor control in mice and other rodents. However, such advances have been elusive in non-human primates (NHPs). While many studies demonstrate expression of reporter proteins, few studies have provided clear quantitative evidence of whether these viral constructs can be reliably used for assessment of in vivo and in vitro function in primates, which, in turn, has hindered widespread adoption by NHP researchers. Here, we characterize putative pan-inhibitory cell targeting vectors engineered with regions from the Dlx5-6 intergenic domain. Pan-inhibitory viral vectors are attractive because they enable ground-truth optotagging and modulation of multiple inhibitory subtypes in the same animal and, when combined with machine learning approaches, enable cell-type classifiers for NHPs. We combined in vivo anesthetized electrophysiological recordings, in vitro slice electrophysiology, and immunohistochemistry across seven rhesus macaque monkeys to assess the specificity, completeness and efficacy of three constructs in multiple sensory and higher-order association cortices. The vectors reliably restricted transgene expression to inhibitory neurons (81-97%). However, of the local GABAergic neurons only 32-64% expressed the transgene, depending on the construct. This incompleteness arose in part from uneven coverage across subtypes, with strong transgene expression in parvalbumin-positive interneurons (~60-90%), sparse expression in calbindin-positive interneurons (~1-7%), and near-complete avoidance of calretinin-positive interneurons. A construct pairing DLX2.0 with ChrimsonR was excellent for in vivo optotagging, while h56D paired with bReaChES most effectively suppressed neural activity in vivo. In the slice, activating terminals of transgene-expressing neurons optically evoked inhibitory currents in coupled pyramidal neurons confirming transsynaptic functionality of these constructs and their use for inhibitory circuit-specific synaptic assessments and manipulation. Collectively, the results provide rigorous functional characterization, and quantitative guidance for NHP researchers seeking to deploy GABAergic cell-type-specific tools in their experiments.

neuroscience↗

bioRxiv2026

Molecular anatomy of the entorhinal cortex

The entorhinal cortex (EC) is critical for episodic memory formation and is the epicenter of neurofibrillary tangle formation in Alzheimer's disease. Its cytoarchitectonic and functional heterogeneity has been recognized for decades, but the molecular underpinnings of this heterogeneity are still relatively uncharted. While many features of the region appear to be conserved between rodents and primates, very little is known about the conservation of the molecular identity of EC neurons. Here we perform single-nucleus RNAseq (snRNAseq) of the mouse EC and use in situ hybridization, as well as publicly available transcriptomics data, to enhance the understanding of the heterogeneity of neuron types present in the area. While the well-known dichotomy between lateral and medial EC is evident in superficial layers of EC, we highlight that the medioventral region of EC forms a different population from the caudomedial section. We identify molecular correlates for the previously described parcellation of lateral EC, and show that, at least in layer IIa, subterritories of EC are not separated by abrupt borders but rather form smooth gradients. Lastly, we show that both lateral vs. medial ECIIa markers, and markers that reveal finer grain heterogeneity within ECIIa have conserved patterns of expression in macaque, highlighting the high degree of homology between the two species. Overall this molecular atlas of the mouse EC with some comparative elements is a resource for anatomically-informed molecular studies of the EC and lays the groundwork for mechanistic studies of selective neuronal vulnerability of the region in the context of AD.

neuroscience↗

bioRxiv2026

Entorhinal Cortex Wolframin-1-expressing neurons propagate tau to CA1 neurons and impair hippocampal memory

Tau pathology emerges early in Alzheimers disease within entorhinal cortex layer II (ECII) and reaches hippocampal CA1, but how this circuit-level spread translates into sex-dependent vulnerability remains unclear. Using a circuit-defined model in which P301L human tau is expressed selectively in Wolframin-1 (Wfs1+) ECII neurons and propagates to CA1, we found that the extent and proximal-distal distribution of tau-positive CA1 neurons were comparable in males and females. Despite similar propagation, females exhibited broad hippocampal-dependent cognitive impairment (working memory, object recognition, fear acquisition, trace associative memory, and contextual fear memory), whereas males showed a selective deficit in trace associative memory. Consistent with these behavioral outcomes, CA1 pyramidal neurons in tau-propagated females displayed reduced excitability (slower action potential kinetics, reduced firing during depolarizing steps) and reduced spontaneous excitatory postsynaptic current (EPSC) amplitude, while males showed subtler intrinsic changes with altered EPSC kinetics. Bulk RNA sequencing of entorhinal cortex and CA1 revealed robust immune pathway engagement after tau propagation, with males showing a stronger Th1/Th2 and neuroinflammatory signature and CTLA4-associated signaling changes, whereas females showed prominent complement-phagosome pathway enrichment and a female-specific increase in Clec7a+ microglia density in CA1. CD4+ T-cell infiltration into CA1 was detected in both sexes. Together, these results indicate that sex-specific neuroimmune programs, rather than differences in tau propagation load, shape CA1 electrophysiological dysfunction and the breadth of memory impairment following early entorhinal-to-hippocampal tau spread.

neuroscience↗

bioRxiv2025

Transcriptional and functional profiles of muscarinic receptor-expressing neurons in primate lateral prefrontal and anterior cingulate cortices

Acetylcholine modulates anterior cingulate (ACC) and lateral prefrontal (LPFC) cortices for cognitive-motivational integration, via specific m1-m4 muscarinic receptors (mAChR) encoded by CHRM1-4 genes. Single-nucleus RNA sequencing and mRNA-protein histology in macaques revealed CHRM3 to be the most enriched mAChR gene in neurons, while m1 predominates at the protein level, likely due to nuclear retention of CHRM3 and cytoplasmic trafficking of CHRM1. CHRM3 and CHRM1 showed strong co-expression and functional overlap, and were transcriptomically-distinct from CHRM2, which was uniquely enriched in deep layer excitatory and PVALB+ inhibitory neurons. Although CHRM+ cell distributions were similar between areas, CHRM1-3+ excitatory neurons in ACC exhibited upregulation of synaptic plasticity genes relative to LPFC. Functional in vitro experiments confirm a more robust cholinergic-mediated decrease in excitatory:inhibitory synaptic ratio in ACC than in LPFC neurons, accompanied by compensatory changes in spine morphology. These findings highlight region-specific acetylcholine signaling essential for flexible processing, learning and memory.

neuroscience↗

bioRxiv2023

Comparative Features of Calretinin, Calbindin and Parvalbumin Expressing Interneurons in Mouse and Monkey Primary Visual and Frontal Cortices

Much is known about differences in pyramidal cells across cortical areas and species, but studies of interneurons have focused on comparisons within single cortical areas and/or species. Here we quantified the distribution and somato-dendritic morphology of interneurons expressing one or more of the calcium binding proteins (CaBPs) calretinin (CR), calbindin (CB) and/or parvalbumin (PV) in mouse (Mus musculus) versus rhesus monkey (Macaca mulatta) in two functionally and cytoarchitectonically distinct regions- the primary visual and frontal cortical areas. The density, laminar distribution and morphology of interneurons were assessed in serial brain sections using immunofluorescent multi-labeling, stereological counting and 3D reconstructions. There were significantly higher densities of CB+ and PV+ neurons in visual compared to frontal areas in both species. The main species difference was the significantly greater density and proportion of CR+ interneurons and lower extent of CaBP co-expression in monkey compared to mouse cortices. Cluster analyses revealed that the somato-dendritic morphology of layer 2-3 inhibitory interneurons is more dependent on CaBP expression than on species and area. Only modest effects of species were observed for CB+ and PV+ interneuron morphologies, while CR+ neurons showed no difference. By contrast to pyramidal cells which show highly distinctive area- and species-specific features, here we found more subtle differences in the distribution and features of interneurons across areas and species. These data yield insight into how nuanced differences in the population organization and properties of neurons may underlie specializations in cortical regions to confer species and area-specific functional capacities. Key PointsO_LISomato-dendritic morphology of distinct interneurons did not substantially scale and vary across areas and species- differences were mainly dependent on CaBP expression. C_LIO_LICortical diversity in inhibitory function across areas and species is thus likely to be derived from differential laminar distribution and densities of distinct interneuron subclasses. C_LIO_LIIn contrast to pyramidal cells which differ widely in distribution and morphology across areas and species, the features of interneurons appears to be relatively more conserved across areas and species. C_LI

neuroscience↗

bioRxiv2023

Neuronal properties of pyramidal cells in lateral prefrontal cortex of the aging rhesus monkey brain are associated with performance deficits on spatial working memory but not executive function.

Age-related declines in cognitive abilities occur as early as middle-age in humans and rhesus monkeys. Specifically, performance by aged individuals on tasks of executive function (EF) and working memory (WM) is characterized by greater frequency of errors, shorter memory spans, increased frequency of perseverative responses, impaired use of feedback and reduced speed of processing. However, how aging precisely differentially impacts specific aspects of these cognitive functions and the distinct brain areas mediating cognition are not well understood. The prefrontal cortex (PFC) is known to mediate EF and WM and is an area that shows a vulnerability to age-related alterations in neuronal morphology. In the current study, we show that performance on EF and WM tasks exhibited significant changes with age and these impairments correlate with changes in biophysical properties of L3 pyramidal neurons in lateral LPFC (LPFC). Specifically, there was a significant age-related increase in excitability of Layer 3 LPFC pyramidal neurons, consistent with previous studies. Further, this age-related hyperexcitability of LPFC neurons was significantly correlated with age-related decline on a task of WM, but not an EF task. The current study characterizes age-related performance on tasks of WM and EF and provides insight into the neural substrates that may underlie changes in both WM and EF with age.

neuroscience↗

bioRxiv2020

Elucidating the pathogenic mechanisms of AD brain-derived tau-containing extracellular vesicles: Highly transmissible and preferential propagation to GABAergic neurons

Extracellular vesicles (EVs) propagate tau pathology for Alzheimers disease (AD). How EV transmission influences AD are, nonetheless, poorly understood. To these ends, the physicochemical and molecular structure-function relationships of human brain-derived EVs, from AD and prodromal AD (pAD), were compared to non-demented controls (CTRL). AD EVs were shown to be significantly enriched in epitope-specific tau oligomers versus pAD or CTRL EVs assayed by dot-blot and atomic force microscopy tests. AD EVs were efficiently internalized by murine cortical neurons and transferred tau with higher aggregation potency than pAD and CTRL EVs. Strikingly, inoculation of tau-containing AD EVs into the outer molecular layer of the dentate gyrus induced tau propagation throughout the hippocampus. This was seen in 22 months-old C57BL/6 mice at 4.5 months post-injection by semiquantitative brain-wide immunohistochemistry tests with multiple anti-phospho-tau (p-tau) antibodies. Inoculation of the equal amount of tau from CTRL EVs or as oligomer or fibril-enriched fraction from the same AD donor showed little propagation. AD EVs induced tau accumulation in the hippocampus as oligomers or sarkosyl-insoluble proteins. Unexpectedly, p-tau cells were mostly GAD67+ GABAergic neurons and to a lesser extent, GluR2/3+ excitatory mossy cells, showing preferential EV-mediated GABAergic neuronal tau propagation. Whole-cell patch clamp recording of Cornu Ammonis (CA1) pyramidal cells showed significant reduction in the amplitude of spontaneous inhibitory post-synaptic currents. This was accompanied by reductions in c-fos+ GAD67+GABAergic neurons and GAD67+ GABAergic neuronal puncta surrounding pyramidal neurons in the CA1 region confirming reduced interneuronal projections. Our study posits a novel tau-associated pathological mechanism for brain-derived EVs.

neuroscience↗

bioRxiv2019

Network models predict that pyramidal neuron hyperexcitability and synapse loss in the dlPFC lead to age-related spatial working memory impairment in rhesus monkeys

Behavioral studies have shown spatial working memory impairment with aging in several animal species, including humans. Persistent activity of layer 3 pyramidal dorsolateral prefrontal cortex (dlPFC) neurons during delay periods of working memory tasks is important for encoding memory of the stimulus. In vitro studies have shown that these neurons undergo significant age-related structural and functional changes, but the extent to which these changes affect neural mechanisms underlying spatial working memory is not understood fully. Here we confirm previous studies showing impairment on the Delayed Recognition Span Task in the spatial condition (DRSTsp), and increased in vitro action potential firing rates (hyperexcitability), across the adult life span of the rhesus monkey. We use a bump attractor model to predict how empirically observed changes in the aging dlPFC affect performance on the Delayed Response Task (DRT), and introduce a model of memory retention in the DRSTsp. Persistent activity--and, in turn, cognitive performance--in both models was affected much more by hyperexcitability of pyramidal neurons than by a loss of synapses. Our DRT simulations predict that additional changes to the network, such as increased firing of inhibitory interneurons, are needed to account for lower firing rates during the DRT with aging reported in vivo. Synaptic facilitation was an essential feature of the DRSTsp model, but it did not compensate fully for the effects of the other age-related changes on DRT performance. Modeling pyramidal neuron hyperexcitability and synapse loss simultaneously led to a partial recovery of function in both tasks, with the simulated level of DRSTsp impairment similar to that observed in aging monkeys. This modeling work integrates empirical data across multiple scales, from synapse counts to cognitive testing, to further our understanding of aging in non-human primates.

neuroscience↗