Biology subjects

Mabry, S. J.

Publications and source records attributed to Mabry, S. J..

6 recordsLinked to original sources

bioRxiv2026

AI-guided analysis of human pancreatic islet sociology reveals distinct cell compositional changes in type 1 diabetes

Human pancreatic islets exhibit greater anatomic and cellular heterogeneity than previously appreciated, raising fundamental questions about how their composition varies with age, sex, region, and islet size and how type 1 diabetes (T1D) alters these relationships. Yet these questions remained largely unresolved due to the bottleneck of manual tissue inspection. Here, we developed an integrated artificial intelligence (AI)-guided imaging, processing, and statistical pipeline enabling unbiased, high-throughput analysis of more than 2 million candidate islets from 106 non-diabetic (ND) and T1D donors. We identified age-, region-, sex-, and islet size-dependent differences in islet distribution and composition between ND and T1D donors. Profound {beta}-cell loss in T1D was accompanied by reciprocal -cell expansion, whereas {delta}-cells and pancreatic polypeptide cells were largely resilient. Cell area and pseudotime analyses uncovered regional and age-dependent trajectories of islet remodeling across T1D progression, along with distinct patterns of cytoarchitectural reorganization of the endocrine pancreas.

pathology↗

bioRxiv2025

Fusobacteria nucleatum determines the expression of amphetamine-induced behavioral responses through an epigenetic phenomenon.

Amphetamines (AMPHs) are psychostimulants commonly used for the treatment of neuropsychiatric disorders. They are also misused (AMPH use disorder; AUD), with devastating outcomes. Recent studies have implicated dysbiosis in the pathogenesis of AUD. However, the mechanistic roles of microbes in AUD are unknown. Fusobacterium nucleatum (Fn) is a bacterium that increases in abundance in both rats and humans upon AMPH exposure. Fn releases short-chain fatty acids (SCFAs), bacterial byproducts thought to play a fundamental role in the gut-brain axis as well as the pathogenesis of AUD. We demonstrate that in gnotobiotic Drosophila melanogaster, colonization with Fn or dietary supplementation of the SCFA butyrate, a potent inhibitor of histone deacetylases (HDACs), enhances the psychomotor and rewarding properties of AMPH as well as its ability to promote male sexual motivation. Furthermore, solely HDAC1 RNAi targeted inhibition recapitulates these enhancements, pointing to a specific process underlying this Fn phenomenon. Of note is that the expression of these AMPH behaviors is determined by the increase in extracellular dopamine (DA) levels that result from AMPH-induced reversal of DA transporter (DAT) function, termed non-vesicular DA release (NVDR). The magnitude of AMPH-induced NVDR is dictated, at least in part, by DAT expression levels. Consistent with our behavioral data, we show that Fn, butyrate, and HDAC1 inhibition enhance NVDR by elevating DAT expression. Thus, the participation of Fn in AUD stems from its ability to release butyrate and inhibit HDAC1. These data offer a microbial target and probiotic interventions for AUD treatment.

neuroscience↗

bioRxiv2024

Aging disrupts the coordination between mRNA and protein expression in mouse and human midbrain

Age-related dopamine (DA) neuron loss is a primary feature of Parkinsons disease. However, it remains unclear whether similar biological processes occur during healthy aging, albeit to a lesser degree. We therefore determined whether midbrain DA neurons degenerate during aging in mice and humans. In mice, we identified no changes in midbrain neuron numbers throughout aging. Despite this, we found age-related decreases in midbrain mRNA expression of tyrosine hydroxylase (Th), the rate limiting enzyme of DA synthesis. Among midbrain glutamatergic cells, we similarly identified age-related declines in vesicular glutamate transporter 2 (Vglut2) mRNA expression. In co-transmitting Th+/Vglut2+ neurons, Th and Vglut2 transcripts decreased with aging. Importantly, striatal Th and Vglut2 protein expression remained unchanged. In translating our findings to humans, we found no midbrain neurodegeneration during aging and identified age-related decreases in TH and VGLUT2 mRNA expression similar to mouse. Unlike mice, we discovered diminished density of striatal TH+ dopaminergic terminals in aged human subjects. However, TH and VGLUT2 protein expression were unchanged in the remaining striatal boutons. Finally, in contrast to Th and Vglut2 mRNA, expression of most ribosomal genes in Th+ neurons was either maintained or even upregulated during aging. This suggests a homeostatic mechanism where age-related declines in transcriptional efficiency are overcome by ongoing ribosomal translation. Overall, we demonstrate species-conserved transcriptional effects of aging in midbrain dopaminergic and glutamatergic neurons that are not accompanied by marked cell death or lower striatal protein expression. This opens the door to novel therapeutic approaches to maintain neurotransmission and bolster neuronal resilience.

neuroscience↗

bioRxiv2023

Sexually dimorphic mechanisms of VGLUT-mediated protection from dopaminergic neurodegeneration

Parkinsons disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and Drosophila ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. We discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT+ DA neurons in mice and flies identified candidate genes that we functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. We discovered transcription factors modulating dVGLUT-dependent DA neuroprotection and identified dj-1{beta} as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health.

neuroscience↗

bioRxiv2022

Syntaxin1 Ser14 Phosphorylation is Required for Non-Vesicular Dopamine Release

Amphetamine (AMPH), a psychostimulant commonly prescribed for the treatment of neuropsychiatric and neurological disorders, has a high liability for abuse. The abuse and psychomotor stimulant properties of AMPH are primarily associated with its ability to increase dopamine (DA) neurotransmission. This increase is mediated, in large part, by non-vesicular DA release (DA efflux). DA efflux is the result of reversal of the DA transporter (DAT) promoted by AMPH. Syntaxin 1 (Stx1) is a SNARE protein that plays a pivotal role in vesicular release. Previously, we have shown that Stx1 also interacts with the distal DAT N-terminus, an event promoted by AMPH. Stx1 is phosphorylated at Ser14 by casein kinase II (CK2). Using Drosophila Melanogaster as an animal model, we show that this phosphorylation event is critical for non-vesicular DA release and regulates the expression of AMPH preference as well as the ability of AMPH to promote mating drive. We also show that reverse transport of DA mediated by DAT underlies these complex behaviors promoted by AMPH. Our molecular dynamics (MD) simulations of the phosphorylated DAT/Stx1 complex demonstrate that the phosphorylation state of these proteins plays a key role in allowing DAT to dwell in an efflux-willing state. This state also supports constitutive DA efflux (CDE), an event that occurs in the absence of AMPH. The DAT-Stx1 phosphorylated complex is characterized by the breakdown of two key salt bridges in DAT, K66-D345 and E428-R445, which are critical for the formation of the intracellular (IC) gate and for transport function. The breaking of these salt bridges leads to an opening and hydration of the DAT intracellular vestibule, allowing DA to bind from the cytosol, a mechanism that we hypothesize leads to CDE. We further determine the importance of Stx1 phosphorylation in CDE by pharmacologically inhibiting CK2 with CX-4945, a molecule currently in phase II clinical trials for cancer treatment. CX-4945 treatment prevented the expression of CDE in isolated Drosophila Melanogaster brains as well as behaviors associated with CDE. Thus, our results suggest that Stx1 phosphorylation is a possible pharmacological target for the treatment of AMPH abuse.

neuroscience↗

bioRxiv2021

Psychomotor impairments and therapeutic implications revealed by a mutation linked with Infantile Parkinsonism-Dystonia

Parkinson disease (PD) is a progressive, neurodegenerative disorder affecting over 6.1 million people worldwide. Although the cause of PD remains unclear, studies of highly-penetrant mutations identified in early-onset familial parkinsonism have contributed to our understanding of the molecular mechanisms underlying disease pathology. Dopamine (DA) transporter (DAT) deficiency syndrome (DTDS) is a distinct type of infantile parkinsonism-dystonia that shares key clinical features with PD, including motor deficits (progressive bradykinesia, tremor, hypomimia) and altered DA neurotransmission. Here, we define structural, functional, and behavioral consequences of a Cys substitution at R445 in human DAT (hDAT R445C), identified in a patient with DTDS. We found that this R445 substitution disrupts a phylogenetically conserved intracellular (IC) network of interactions that compromise the hDAT IC gate. This is demonstrated by both Rosetta molecular modeling and fine-grained simulations using hDAT R445C, as well as EPR analysis and X-ray crystallography of the bacterial homolog leucine transporter. Notably, the disruption of this IC network of interactions supported a channel-like intermediate of hDAT and compromised hDAT function. We demonstrate that Drosophila melanogaster expressing hDAT R445C show impaired hDAT activity, which is associated with DA dysfunction in isolated brains and with abnormal behaviors monitored at high-speed time resolution. We show that hDAT R445C Drosophila exhibit motor deficits, lack of motor coordination (i.e. flight coordination) and phenotypic heterogeneity in these behaviors that is typically associated with DTDS and PD. These behaviors are linked with altered dopaminergic signaling stemming from loss of DA neurons and decreased DA availability. We rescued flight coordination through enhanced DAT surface expression via the lysosomal inhibitor chloroquine. Together, these studies shed light on how a DTDS-linked DAT mutation underlies DA dysfunction and, more broadly, the clinical phenotypes shared by DTDS and PD.

neuroscience↗