Biology subjects

Alcantara-Gonzalez, D.

Publications and source records attributed to Alcantara-Gonzalez, D..

5 recordsLinked to original sources

bioRxiv2026

A user-friendly single-nucleus RNA sequencing pipeline to identify alterations in gene expression in small brain circuits

Single-cell or single-nucleus RNA sequencing are common methods to investigate gene expression. However, to clarify the genes in specific types of cells in a small circuit there are limitations to current approaches. Here we present modifications to standard protocols to overcome the limitations and do so in a manner that will be accessible to novices. Then the modified methods are applied to a question about a small area of the brain, the dentate gyrus (DG) of the mouse, where information about cell types was of interest. The question arose from data acquired in a mouse model of Alzheimers disease where early hyperactivity of the principal cells, granule cells (GCs), was identified that was difficult to explain by existing data. Therefore, we investigated altered gene expression in GCs, and other DG cell types that influence GCs, to identify putative mechanisms. Validations of the modified methods are addressed, comparisons are made to other methods, and comparisons of mouse and human data are presented.

neuroscience↗

bioRxiv2024

Increased excitability of dentate gyrus mossy cells occurs early in life in the Tg2576 model of Alzheimer's disease.

INTRODUCTIONHyperexcitability in Alzheimers disease (AD) emerge early and contribute to disease progression. The dentate gyrus (DG) is implicated in hyperexcitability in AD. We hypothesized that mossy cells (MCs), regulators of DG excitability, contribute to early hyperexcitability in AD. Indeed, MCs generate hyperexcitability in epilepsy. METHODSUsing the Tg2576 model and WT mice ([~]1month-old), we compared MCs electrophysiologically, assessed c-Fos activity marker, A{beta} expression and mice performance in a hippocampal-dependent memory task. RESULTSTg2576 MCs exhibit increased spontaneous excitatory events and decreased inhibitory currents, increasing the charge transfer excitation/inhibition ratio. Tg2576 MC intrinsic excitability was enhanced, and showed higher c-Fos, intracellular A{beta} expression, and axon sprouting. Granule cells only showed changes in synaptic properties, without intrinsic changes. The effects occurred before a memory task is affected. DISCUSSIONEarly electrophysiological and morphological alterations in Tg2576 MCs are consistent with enhanced excitability, suggesting an early role in DG hyperexcitability and AD pathophysiology. HIGHLIGHTS{circ} MCs from 1 month-old Tg2576 mice had increased spontaneous excitatory synaptic input. {circ}Tg2576 MCs had reduced spontaneous inhibitory synaptic input. {circ}Several intrinsic properties were abnormal in Tg2576 MCs. {circ}Tg2576 GCs had enhanced synaptic excitation but no changes in intrinsic properties. {circ}Tg2576 MCs exhibited high c-Fos expression, soluble A{beta} and axonal sprouting.

neuroscience↗

bioRxiv2023

Choline supplementation in early life improves and low levels of choline can impair outcomes in a mouse model of Alzheimer's disease.

Maternal choline supplementation (MCS) improves cognition in Alzheimers disease (AD) models. However, effects of MCS on neuronal hyperexcitability in AD are unknown. We investigated effects of MCS in a well-established mouse model of AD with hyperexcitability, the Tg2576 mouse. The most common type of hyperexcitability in Tg2576 mice are generalized EEG spikes (interictal spikes; IIS). IIS also are common in other mouse models and occur in AD patients. Im mouse models, hyperexcitability is also reflected by elevated expression of the transcription factor {Delta}FosB in the granule cells (GCs) of the dentate gyrus (DG), which are the principal cell type. Therefore we studied {Delta}FosB expression in GCs. We also studied the the neuronal marker NeuN within hilar neurons of the DG because other studies have reduced NeuN protein expression is a sign of oxidative stress or other pathology. This is potentially important because hilar neurons regulate GC excitability. Tg2576 breeding pairs received a diet with a relatively low, intermediate or high concentration of choline. After weaning, all mice received the intermediate diet. In offspring of mice fed the high choline diet, IIS frequency declined, GC {Delta}FosB expression was reduced, and NeuN expression was restored. Using the novel object location task, spatial memory improved. In contrast, offspring exposed to the relatively low choline diet had several adverse effects, such as increased mortality. They had the weakest hilar NeuN immunoreactivity and greatest GC {Delta}FosB protein expression. However, their IIS frequency was low, which was surprising. The results provide new evidence that a diet high in choline in early life can improve outcomes in a mouse model of AD, and relatively low choline can have mixed effects. This is the first study showing that dietary choline can regulate hyperexcitability, hilar neurons, {Delta}FosB and spatial memory in an animal model of AD.

neuroscience↗

bioRxiv2020

Early changes in synaptic and intrinsic properties of dentate gyrus granule cells in a mouse model of Alzheimer's disease neuropathology and atypical effects of the cholinergic antagonist atropine.

It has been reported that hyperexcitability occurs in a subset of patients with Alzheimers disease (AD) and hyperexcitability could contribute to the disease. Several studies have suggested that the hippocampal dentate gyrus (DG) may be an important area where hyperexcitability occurs. Therefore, we tested the hypothesis that the principal DG cell type, granule cells (GCs), would exhibit changes at the single-cell level which would be consistent with hyperexcitability and might help explain it. We used the Tg2576 mouse, where it has been shown that hyperexcitability is robust at 2-3 months of age. GCs from 2-3-month-old Tg2576 mice were compared to age-matched wild type (WT) mice. Effects of muscarinic cholinergic antagonism were tested because previously we found that Tg2576 mice exhibited hyperexcitability in vivo that was reduced by the muscarinic cholinergic antagonist atropine, counter to the dogma that in AD one needs to boost cholinergic function. The results showed that GCs from Tg2576 mice exhibited increased frequency of spontaneous excitatory postsynaptic potentials/currents (sEPSP/Cs) and reduced frequency of spontaneous inhibitory synaptic events (sIPSCs) relative to WT, increasing the excitation:inhibition (E:I) ratio. There was an inward glutamatergic current that we defined here as a novel synaptic current (nsC) in Tg2576 mice because it was very weak in WT mice. Although not usually measured, intrinsic properties were distinct in Tg2576 GCs relative to WT. In summary, GCs of the Tg2576 mouse exhibit early electrophysiological alterations that are consistent with increased synaptic excitation, reduced inhibition, and muscarinic cholinergic dysregulation. The data support previous suggestions that the DG and cholinergic system contribute to hyperexcitability early in life in AD mouse models. HIGHLIGHTSO_LIGranule cells (GCs) in young Tg2576 mice had abnormal synaptic activity. C_LIO_LIYoung Tg2576 GCs had increased excitatory and reduced inhibitory synaptic activity. C_LIO_LIGC intrinsic properties were altered in young Tg2576 mice. C_LIO_LIMuscarinic cholinergic regulation of GCs was altered in young Tg2576 mice. C_LIO_LIAtropine led to a novel spontaneous inward current that was very strong in Tg2576 GCs. C_LI

neuroscience↗

bioRxiv2020

Dorsal and ventral mossy cells differ in their long-range axonal projections throughout the dentate gyrus of the mouse hippocampus

Glutamatergic hilar mossy cells (MCs) have axons that terminate both near and far from their cell body but stay within the DG, making synapses in the inner molecular layer primarily. The long-range axons are considered the primary projection, and extend throughout the DG ipsilateral to the soma, and project to the contralateral DG. The specificity of long-range MC axons for the inner molecular layer (IML) has been considered to be a key characteristic of the DG. In the present study we made the surprising finding that dorsal MC axons are an exception to this rule. We used two mouse lines that allow for Cre-dependent viral labeling of MCs and their axons: dopamine receptor d2 (Drd2-Cre) and calcitonin receptor-like receptor (Crlr-Cre). A single viral injection into the dorsal DG to label dorsal MCs resulted in labeling of MC axons in both the IML and middle molecular layer (MML). Interestingly, this broad termination of MC axons applied to all long-range axons. In contrast, long-range axons of ventral MCs mainly terminated in the IML, consistent with the literature. Taken together, these results suggest that dorsal and ventral MCs differ significantly in their axonal projections, and the difference is primarily in their long-range projections. Since those projections are thought to terminate primarily on GCs, the results suggest a dorsal-ventral difference in MC activation of GCs. The surprising difference in dorsal and ventral MC projections should therefore be considered when evaluating dorsal-ventral differences in DG function.

neuroscience↗