Biology subjects

Borgenheimer, E.

Publications and source records attributed to Borgenheimer, E..

4 recordsLinked to original sources

bioRxiv2024

Cerebellar contribution to cognitive deficits and prefrontal cortex dysfunction in Spinocerebellar Ataxia Type 1 (SCA1)

The cerebellums role in cognition and its functional bi-directional connectivity with prefrontal cortex (PFC) is now recognized. However, how chronic cerebellar dysfunction affects PFC function and cognition remains less understood. Spinocerebellar ataxia type 1 (SCA1), is an inherited, fatal neurodegenerative disease caused by an abnormal expansion of glutamine (Q) encoding CAG repeats in the gene Ataxin-1 (ATXN1) and characterized by severe loss of Purkinje cells (PCs) in the cerebellum. Patients with SCA1 suffer from movement and balance deficits, cognitive decline and premature lethality. Cognitive deficits significantly impact patients quality of life, yet how exactly cerebellar degeneration contributes to cognitive deficits and PFC dysfunction in SCA1 is unknown. We have previously demonstrated that expression of mutant ATXN1 only in cerebellar Purkinje cells (PCs) is sufficient to cause cognitive deficits in a transgenic ATXN1[82Q] mouse line. To understand how cerebellar dysfunction impacts the PFC, we examined neuronal activity, synaptic density, and gene expression changes in the PFC of ATXN1[82Q] mice. Remarkably, we found decreased neuronal activity, reduced synaptic density, and altered expression of immediate early genes and pathways involved in glucose metabolism, inflammation and amphetamine in the PFC of ATXN1[82Q] mice. Furthermore, we characterized cellular and molecular PFC dysfunction in a novel conditional knock-in SCA1 line, f-ATXN1146Q mice, expressing floxed human expanded ATXN1 throughout the brain. Intriguingly, we found an increased number of neurons, increased synaptic density and large gene expression alterations in the PFC of f-ATXN1146Q mice. Finally, to precisely determine the role of cerebellar dysfunction in cognitive deficits and PFC dysfunction in SCA1, we crossed f-ATXN1146Q mice with Pcp2-Cre mice expressing Cre recombinase in PCs to delete expanded ATXN1 only in PCs. Surprisingly, we have found that deleting expanded ATXN1 in PCs exacerbated cognitive deficits and PFC dysfunction in these mice. Our findings demonstrate that circumscribed cerebellar dysfunction is sufficient to impact PFC activity and synaptic connectivity impairing cognition. However, when multiple brain regions are impacted in disease, cerebellar dysfunction may ameliorate PFC pathology and cognitive performance.

neuroscience↗

bioRxiv2021

Single-nuclei RNA sequencing uncovers non-cell autonomous changes in cerebellar astrocytes and oligodendrocytes that may contribute to Spinocerebellar Ataxia Type 1 (SCA1) pathogenesis

Glial cells, including astrocytes and oligodendrocytes are important for normal brain function. In many neurodegenerative diseases glial cells undergo significant morphological, functional and gene expression changes termed reactive gliosis. The cause, identity and neuroprotective or neurotoxic nature of these changes remains incompletely understood. This knowledge in needed to develop a framework of how individual pathological changes in glial cells contribute to progressive dysfunction and selective neuronal vulnerability in neurodegenerative diseases. This is particularly relevant during the early disease stages that allow for the effective therapies and reversal or slowing of disease phenotypes. Spinocerebellar ataxia type 1 (SCA1) is a progressive neurodegenerative disease caused by an abnormal expansion of CAG repeats in the gene Ataxin1 (ATXN1). While mutant ATXN1 is expressed broadly throughout the brain, SCA1 is characterized by severe degeneration of cerebellar Purkinje cells (PCs). Despite major advances in dissecting the effects of mutant ATXN1 on Purkinje cells, much less is understood how cerebellar astrocytes and oligodendrocytes respond to and contribute to Purkinje cell dysfunction in SCA1. To address this question we performed cerebellar single nuclei RNA sequencing (snRNA seq) of early disease stage Pcp2-ATXN1[82Q] mice, a transgenic SCA1 mouse model expressing mutant ATXN1 only in Purkinje cells. We found no changes in cell numbers in the SCA1 cerebellum. We validated previously indicated pathway and gene expression changes in the Purkinje cells, and identified novel DEG and pathways in Purkinje cells, including Ralyl that may provide compensatory roles and maintain PC function. Importantly we identified profound non-cell autonomous and potentially neuroprotective gene expression and pathway alterations in Bergman glia, velate astrocytes and oligodendrocytes that may contribute to disease pathogenesis.

neuroscience↗

bioRxiv2021

Early stage of Spinocerebellar Ataxia Type 1 (SCA1) progression exhibits region- and cell-specific pathology and is partially ameliorated by Brain Derived Neurotrophic Factor (BDNF)

While astrocyte heterogeneity is an important feature of the healthy brain, less is understood about spatiotemporal heterogeneity of astrocytes in brain disease. Spinocerebellar ataxia type 1 (SCA1) is a progressive neurodegenerative disease caused by a CAG repeat expansion mutation in the gene Ataxin1 (ATXN1). We characterized astrocytes across disease progression in the four clinically relevant brain regions, cerebellum, brainstem, hippocampus, and motor cortex of Atxn1154Q/2Q mice, a knock-in mouse model of SCA1. We found brain region specific changes in astrocyte density, GFAP expression and area, early in disease and prior to neuronal loss. Expression of astrocytic core homeostatic genes was also altered in a brain-region specific manner and correlated with neuronal activity indicating that astrocytes may compensate or exacerbate neuronal dysfunction in a brain region specific manner. Late in disease, expression of astrocytic homeostatic genes was reduced in all four brain regions indicating loss of astrocyte functions. We observed spatiotemporal changes in microglia with no obvious correlation with spatiotemporal astrocyte alterations indicating a complex orchestration of glial phenotypes in disease. These results support spatiotemporal diversity of glial phenotypes as an important feature of the brain disease that may contribute to SCA1 pathogenesis in a brain-region and disease stage-specific manner.

neuroscience↗

bioRxiv2017

In vivo clonal analysis reveals spatiotemporal regulation of thalamic nucleogenesis

The thalamus, a crucial regulator of cortical functions, is composed of many nuclei arranged in a spatially complex pattern. Thalamic neurogenesis occurs over a short period during mammalian embryonic development. These features have hampered the effort to understand how regionalization, cell divisions and fate specification are coordinated and produce a wide array of nuclei that exhibit distinct patterns of gene expression and functions. Here, we performed in vivo clonal analysis to track the divisions of individual progenitor cells and spatial allocation of their progeny in the developing mouse thalamus. Quantitative analysis of clone compositions revealed evidence for sequential generation of distinct sets of thalamic nuclei based on the location of the founder progenitor cells. Furthermore, we identified intermediate progenitor cells that produced neurons populating more than one thalamic nuclei, indicating a prolonged specification of nuclear fate. Our study reveals an organizational principle that governs the spatial and temporal progression of cell divisions and fate specification, and provides a framework for studying cellular heterogeneity and connectivity in the mammalian thalamus.

neuroscience↗