Biology subjects

Faust, P. L.

Publications and source records attributed to Faust, P. L..

5 recordsLinked to original sources

bioRxiv2025

A therapeutic role for a regulatory glucose transporter1 (Glut1)-associated natural antisense transcript

The mammalian brain relies primarily on glucose for its energy needs. Delivery of this nutrient to the brain is mediated by the glucose transporter-1 (Glut1) protein. Low Glut1 thwarts glucose entry into the brain, causing an energy crisis and, triggering, in one instance, the debilitating neurodevelopmental condition - Glut1 deficiency syndrome (Glut1DS). Current treatments for Glut1DS are sub-optimal, as none address the root cause - low Glut1 - of the condition. Levels of this transporter must respond rapidly to the brains changing energy requirements. This necessitates fine-tuning its expression. Here we describe a long-noncoding RNA (lncRNA) antisense to Glut1 and show that it is involved in such regulation. Raising levels of the lncRNA had a concordant effect on Glut1 in cultured human cells and transgenic mice; reducing levels elicited the opposite effect. Delivering the lncRNA to Glut1DS model mice via viral vectors induced Glut1 expression, enhancing brain glucose levels to mitigate disease. Direct delivery of such a lncRNA to combat disease has not been reported previously and constitutes a unique therapeutic paradigm. Moreover, considering the importance of maintaining homeostatic Glut1 levels, calibrating transporter expression via the lncRNA could become broadly relevant to the myriad conditions, including Alzheimers disease, wherein Glut1 concentrations are perturbed.

neuroscience↗

bioRxiv2025

Axonal pathology differentially affects human Purkinje cell subtypes in the essential tremor cerebellum

The cerebellar cortex is organized into discrete regions populated by molecularly distinct Purkinje cells (PCs), the sole cortical output neurons. While studies in animal models have shown that PC subtypes differ in their vulnerability to disease, our understanding of human PC subtype and vulnerability remains limited. Here, we demonstrate that human cerebellar regions specialized for motor vs cognitive functions (lobule HV vs Crus I) contain distinct PC populations characterized by specific molecular and anatomical features, which show selective vulnerability in essential tremor (ET), a cerebellar degenerative disorder. Using a known PC subtype marker, neurofilament heavy chain (NEFH), we found that motor lobule HV contains PCs with high NEFH expression, while cognitive lobule Crus I contains PCs with low NEFH expression in post-mortem samples from healthy controls. In the same cerebella, PC axons in lobule HV were 2.2-fold thicker than those in Crus I. Across lobules, axon caliber positively correlated with NEFH expression. In ET cerebella, we identified motor lobule-specific PC axon pathology with a 1.5-fold reduction in caliber and increased axon variability in lobule HV, while Crus I axons were unaffected. Tremor severity and duration in ET correlated with axon diameter variability selectively in lobule HV PCs. Given that axonal caliber is a major determinant of neural signaling capacity, our results (1) suggest that disrupted cerebellar corticonuclear signaling is occurring in ET, (2) provide evidence of region-specific PC subtypes in the human cerebellum and offer insight into how selective PC vulnerability may contribute to the pathophysiology of cerebellar degeneration. Significance StatementThe cerebellar cortex has a uniform laminar architecture but contains heterogeneous cell types. Purkinje cells (PCs), the sole output cells of the cerebellar cortex, include subtypes whose lobular distribution is thought to underlie functional segmentation and patterned degeneration of the cerebellum in animal models. However, human PC subtypes and their disease vulnerability remain unknown. Here, we establish the existence of human PC subtypes that appear conserved across mammalian species using both marker expression and axonal thickness. Consistent with its phenotype, we demonstrate differential PC vulnerability to degeneration in essential tremor cerebella, where motor function- mediating PC subtypes display significant axonal thinning, while axons of cognitive function-mediating PC subtypes are spared. These findings advance Purkinje cell type- oriented research in cerebellar disorders.

neuroscience↗

bioRxiv2024

Essential tremor with tau pathology features seeds indistinguishable in conformation from Alzheimer's disease and primary age-related tauopathy

Neurodegenerative tauopathies are characterized by the deposition of distinct fibrillar tau assemblies whose rigid core structures correlate with defined neuropathological phenotypes. Essential tremor (ET) is a progressive neurological disease disease that, in some cases, is associated with cognitive impairment and tau accumulation.. Consequently, we explored the tau assembly conformation in ET patients with tau pathology using cytometry-based tau biosensor assays. These assays quantify tau prion seeding activity present in brain homogenates based on conversion of intracellular tau-fluorescent protein fusions from a soluble to an aggregated state. Prions exhibit seeding barriers, whereby a specific assembly structure cannot serve as a template for a native monomer if the amino acids are not compatible. We recently exploited the tau prion species barrier to define tauopathies by systematically substituting alanine (Ala) in the tau monomer and measuring its incorporation into seeded aggregates within biosensor cells. The Ala scan precisely classified the conformation of tau seeds from diverse tauopathies. We next studied 18 ET patient brains with tau pathology. Only one case had concurrent high amyloid-{beta} plaque pathology consistent with Alzheimers disease (AD). We detected robust tau seeding activity in 9 (50%) of the patients. This predominantly localized to the temporal pole and temporal cortex. We examined 8 ET cases with the Ala scan and determined that the amino acid requirements for tau monomer incorporation into aggregates seeded from these ET brain homogenates were identical to those of AD and primary age-related tauopathy (PART), and completely distinct from other tauopathies such as corticobasal degeneration, chronic traumatic encephalopathy, and progressive supranuclear palsy. Based on these studies, tau assembly cores in a pathologically confined subset of ET cases with high tau pathology are identical to AD and PART. This could facilitate more precise diagnosis and therapy for ET patients with cognitive impairment.

pathology↗

bioRxiv2021

Longitudinal single-cell transcriptional dynamics throughout neurodegeneration in SCA1

Neurodegeneration is a protracted process involving progressive changes in myriad cell types that ultimately result in neuronal death. Changes in vulnerable neuronal populations are highly influenced by concomitant changes in surrounding cells, complicating experimental approaches to interrogate the simultaneous events that underlie neurodegeneration. To dissect how individual cell types within a heterogeneous tissue contribute to the pathogenesis and progression of a neurodegenerative disorder, we performed longitudinal single-nucleus RNA sequencing of the mouse and human spinocerebellar ataxia type 1 (SCA1) cerebellum, establishing continuous dynamic trajectories of each population. Furthermore, we defined the precise transcriptional changes that precede loss of Purkinje cells and identified early oligodendroglial impairments that can profoundly impact cerebellar function. Finally, we applied a deep learning method to accurately predict disease state and identify drivers of disease. Together, this work uncovers new roles for diverse cerebellar cell types in SCA1 and provides a generalizable analysis framework for studying neurodegeneration.

neuroscience↗

bioRxiv2020

Novel genetic features of human and mouse Purkinje cell differentiation defined by comparative transcriptomics.

Comparative transcriptomics between differentiating human pluripotent stem cells (hPSC) and developing mouse neurons offers a powerful approach to compare genetic and epigenetic pathways in human and mouse neurons. To analyze human Purkinje cell (PC) differentiation, we optimized a protocol to generate hPSC-PCs that formed synapses when cultured with mouse cerebellar glia and granule cells and fired large calcium currents, measured with the genetically encoded calcium indicator jRGECO1a. To directly compare global gene expression of hPSC-PCs with developing mouse PCs, we used translating ribosomal affinity purification (TRAP). As a first step, we used Tg(Pcp2-L10a-Egfp) TRAP mice to profile actively transcribed genes in developing postnatal mouse PCs, and used metagene projection to identify the most salient patterns of PC gene expression over time. We then created a transgenic Pcp2-L10a-Egfp TRAP hESC line to profile gene expression in differentiating hPSC-PCs, finding that the key gene expression pathways of differentiated hPSC-PCs most closely matched those of late juvenile, mouse PCs (P21). Comparative bioinformatics identified classical PC gene signatures as well as novel mitochondrial and autophagy gene pathways during the differentiation of both mouse and human PCs. In addition, we identified genes expressed in hPSC-PCs but not mouse PCs and confirmed protein expression of a novel human PC gene, CD40LG, expressed in both hPSC-PCs and native human cerebellar tissue. This study therefore provides the first direct comparison of hPSC-PC and mouse PC gene expression and a robust method for generating differentiated hPSC-PCs with human-specific gene expression for modeling developmental and degenerative cerebellar disorders. Significance StatementTo compare global gene expression features of differentiating human pluripotent stem cell-derived Purkinje cells (hPSC-PC) and developing mouse Purkinje cells (PC) we derived hPSC-PCs and compared gene expression datasets from human and mouse PCs. We optimized a differentiation protocol that generated hPSC-PCs most similar in gene expression to mouse P21 PCs. Metagene projection analysis of mouse PC gene expression over postnatal development identified both classical PC marker genes as well as novel mitochondrial and autophagy gene pathways. These key gene expression patterns were conserved in differentiating hPSC-PCs. We further identified differences in timing and expression of key gene sets between mouse and hPSC-PCs and confirmed expression of a novel human PC marker, CD40LG, in human cerebellar tissue.

developmental biology↗