Biology subjects

Harris, A. C.

Publications and source records attributed to Harris, A. C..

11 recordsLinked to original sources

bioRxiv2026

The collective effect of non-nicotine constituents on the reinforcing and neuropharmacological effects of comprehensive cigarette smoke and electronic nicotine delivery system (ENDS) aerosol extracts in rats.

Tobacco product extracts containing nicotine and non-nicotine constituents are useful for understanding the collective role of these constituents in tobacco use disorder (TUD). However, few studies have used extracts with both water-soluble and non-water-soluble constituents with accompanying chemical analysis, or compared behavioral and neuropharmacological effects across product types. To address these limitations, we compared the relative abuse liability of cigarette smoke (CS) and electronic nicotine delivery system (ENDS) aerosol (EA) extracts to nicotine alone using intravenous self-administration in rats, and examined effects on nucleus accumbens (NAc) dopamine (DA) release and binding/function at nicotinic acetylcholine receptors (nAChRs) and other addiction-related receptors in vitro. CS extract contained higher levels of several behaviorally active non-nicotine constituents than EA extract. Both extracts produced a downward/leftward shift in the descending limb of the unit dose-response curve relative to nicotine alone, while only CS extract produced greater compensatory increases in responding compared to nicotine alone. Demand intensity (Q0) was lower for CS but not EA extract, relative to nicotine alone, whereas demand elasticity for both extracts was similar to nicotine alone. Stress-induced reinstatement was comparable between CS extract and nicotine alone but attenuated for EA extract. CS extract, but not EA extract, showed greater potency for 4{beta}2 nAChR activation and substantial binding across numerous non-nAChRs (DA, serotonergic, opioid) relative to nicotine alone at a high screening concentration. CS extract, but not nicotine alone, also inhibited cyclooxygenase (COX)-1 and -2 at smoking-relevant concentrations. There was no difference in NAc DA release between formulations. These findings indicate non-nicotine constituents contribute to certain reinforcing and neuropharmacological effects of CS, and to a lesser extent EA. Our finding of COX inhibition by CS extract warrants further investigation as a potential mechanism contributing to the effects of CS and TUD.

pharmacology and toxicology↗

bioRxiv2026

Tumor suppressor-like mutations mark a dosage-constrained dependency in leukemia

Cancer genes are classically categorized as oncogenes or tumor suppressors based on whether gain or loss of function promotes malignancy. Here we show that oncogene-imposed dosage constraints can produce mutations that mimic tumor suppressor loss yet mark essential genes. In acute promyelocytic leukemia (APL), the transcription factor EBF3 gene harbors recurrent heterozygous loss-of-function mutations, a tumor suppressor signature, and is essential for APL survival. We resolve this paradox by showing that while PML::RARA, the fusion oncoprotein defining APL, drives EBF3 expression, excess EBF3 suppresses proliferation. Patient mutations reduce EBF3 activity through heterozygous inactivation, optimizing its expression within a corridor bounded by fitness constraints at both extremes. PML::RARA activates EBF3 via a p300-dependent intronic enhancer, and p300 inhibition exploits this constraint by suppressing EBF3 below the viability threshold. Our findings reveal that oncogenes can impose dosage constraints that drive adaptive mutations conventionally misclassified as tumor suppressor loss, with implications for interpreting cancer genomes.

cancer biology↗

bioRxiv2025

Brain-derived exosome biomarkers of neuroinflammation and neuronal functional iron deficiency in newborns of overweight-obese mothers

BackgroundNon-infectious neuroinflammation (NINI) in early life and neonatal neural iron deficiency (nID) have been proposed to contribute to neurodevelopmental dysfunction and disorders, including autism, through toxic effects on neural cells and impaired molecular signaling. Early detection of NINI and nID may enable interventions to restore neurodevelopmental homeostasis and reduce long-term impact. However, such diagnoses are impossible due to ethical reason to access to the central nervous system (e.g., lumbar puncture) when there is no suspicion of brain infection (e.g., meningitis). MethodsWe refined a methodology to isolate and quantify inflammatory and iron-regulatory proteins in high-quality brain-derived extracellular vesicles (BDEVs) from human umbilical cord blood. A preclinical model was used to validate that BDEV contents reflect the brain microenvironment. We then applied this approach to evaluate biomarkers of NINI and nID in BDEVs isolated from cord plasma of newborns of mothers with obesity, a non-infectious pro-inflammatory gestational condition and a risk factor for nID. FindingsPlasma BDEV analytes correlated more strongly with brain analytes and showed stronger associations among functionally related molecules compared with whole plasma analytes. Maternal obesity induced an anti-inflammatory response in the brain compartment, a pro-inflammatory response in the periphery, and functional nID. InterpretationBDEVs may provide a more sensitive representation of the brain microenvironment than blood-based measures (e.g., plasma), enabling non-invasive, early detection of infants with NINI and neonatal nID. FundingSupported by NIH, the Masonic Institute for Developing Brain, Hennepin Healthcare Research Institute, UnityPoint Health Meriter Foundation, and American Academy of Pediatrics Resident Research Grant. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSPrevious studies hypothesized that gestational inflammatory environments (e.g., maternal obesity) increase risk of neonatal neural iron deficiency (nID), neuroinflammation, and neurodevelopmental disorders. However, assessing non-infectious neuroinflammation (NINI) in infants from these high-risk groups is not feasible or clinically justifiable using invasive methods (e.g., cerebrospinal fluid collection), and analytes from whole blood or plasma may not accurately reflect brain physiological status. Added value of this studyWe refined a protocol to isolate brain-derived extracellular vesicles (BDEVs) from a small amount of plasma sample (100 {micro}L) and characterized their contents to approximate brain physiology. We demonstrated that BDEVs more accurately reflect brain status compared with whole plasma. In newborns of mothers with obesity during pregnancy, we found evidence of a low-grade peripheral inflammation accompanied by a protective anti-inflammatory response in the brain. Maternal obesity was also found to induce neonatal nID. Implications of all the available evidenceBDEVs can serve as an accurate, non-invasive tool to assess brain condition. In clinical settings, this approach may be used for early diagnosis, monitoring disease progression, and evaluating treatment effects. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/648967v2_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@108caa9org.highwire.dtl.DTLVardef@311ecdorg.highwire.dtl.DTLVardef@dd4086org.highwire.dtl.DTLVardef@1b747ea_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

A genotype-first approach identifies variants for orofacial clefts and other phenotypes in dogs

Dog breeding promotes within-group homogeneity through conformation to strict breed standards, and also drives between-group heterogeneity in pursuit of characteristic breed traits. There are over 350 recognized dog breeds that provide the foundation for investigating the genetic basis of phenotypic diversity. Typically, breed standard phenotypes such as stature, fur length, and craniofacial structure are analyzed in genetic association studies. However, such analyses are limited to the assayed phenotypes, leaving difficult to measure phenotypic subtleties potentially overlooked. In this study, the genotype-first approach was adapted to the dog genome to investigate coding variation from over 2000 dogs, leading to discoveries of new mutations related to craniofacial morphology and stature. Breed-enriched variants were prioritized according to gene constraint, which was calculated using a mutation model derived from trinucleotide substitution probabilities in the dog. Among the discovered variants was a splice-acceptor mutation in PDGFRA associated with bifid nose, a characteristic trait of Catalburun dogs, implicating the genes role in midline closure, and a frameshift mutation in LCORL associated with large canine body size, thus highlighting the importance of allelic heterogeneity in selection for breed traits. Most priority variants were not associated with genomic signatures for breed differentiation, as these regions were enriched for constrained genes intolerant to nonsynonymous variation, suggesting a model of breed phenotype diversification based on regulatory changes to essential genes. Identification of trait-associated variants in dogs informs new biological roles for genes. Improved collection of breed disease risk data, along with increased breed representation, will drive further discoveries.

genomics↗

bioRxiv2024

Differential gene expression and chromatin accessibility in the rat medial prefrontal cortex mediating individual variability in vulnerability to opioid use

We characterized gene transcriptional activity in the medial prefrontal cortex of rats associated with individual differences in vulnerability to three distinct phases of opioid use disorder (OUD). Resilient rats showed many more changes in canonical pathway activity than Vulnerable rats in models of both early and advanced OUD, involving passive opioid exposure and opioid self-administration (SA), respectively. The Resilient/Vulnerable phenotype was also associated across phases with functionally specific gene networks, including those mediating epigenetic, neuroimmune, and neuroplasticity function. In contrast, we identified two phase-specific effects. First, differential activity of a myelination-related gene network was associated with Resilience/Vulnerability measured after passive morphine exposure. Second, expression of the calmodulin-inhibitor Pcp4, a gene recently implicated in a rat opioid SA GWAS analysis, was associated with Resilience/Vulnerability measured after SA but not after passive morphine exposure. Thus, we have identified both general and phase-specific transcriptional signatures involved in OUD vulnerability across its trajectory. TeaserAdaptations in the brain transcriptome are associated with resilience and vulnerability to opioid use disorder.

neuroscience↗

bioRxiv2023

A phenotypically robust model of Spinal and Bulbar Muscular Atrophy in Drosophila

Spinal and bulbar muscular atrophy (SBMA) is an X-linked disorder that affects males who inherit the androgen receptor (AR) gene with an abnormal CAG triplet repeat expansion. The resulting protein contains an elongated polyglutamine (polyQ) tract and causes motor neuron degeneration in an androgen-dependent manner. The precise molecular sequelae of SBMA are unclear. To assist with its investigation and the identification of therapeutic options, we report here a new model of SBMA in Drosophila melanogaster. We generated transgenic flies that express the full-length, human AR with a wild-type or pathogenic polyQ repeat. Each transgene is inserted into the same "safe harbor" site on the third chromosome of the fly as a single copy and in the same orientation. Expression of pathogenic AR, but not of its wild-type variant, in neurons or muscles leads to consistent, progressive defects in longevity and motility that are concomitant with polyQ-expanded AR protein aggregation and reduced complexity in neuromuscular junctions. Additional assays show adult fly eye abnormalities associated with the pathogenic AR species. The detrimental effects of pathogenic AR are accentuated by feeding flies the androgen, dihydrotestosterone. This new, robust SBMA model can be a valuable tool towards future investigations of this incurable disease.

neuroscience↗

bioRxiv2022

Concussive head trauma perturbs axon initial segment function in axotomized and intact layer 5 pyramidal neurons

The axon initial segment (AIS) is a critical locus of control of action potential (AP) generation and neuronal information synthesis. Concussive traumatic brain injury gives rise to diffuse axotomy, and the majority of neocortical axonal injury arises at the AIS. Consequently, concussive traumatic brain injury might profoundly disrupt the functional specialization of this region. To investigate this hypothesis, one and two days after mild central fluid percussion injury in Thy1-YFP-H mice, we recorded high-resolution APs from axotomized and adjacent intact layer 5 pyramidal neurons and applied a second derivative (2{degrees}) analysis to measure the AIS- and soma-regional contributions to the AP upstroke. All layer 5 pyramidal neurons recorded from sham animals manifested two stark 2{degrees} peaks separated by a negative intervening slope. In contrast, within injured mice, we discovered a subset of axotomized layer 5 pyramidal neurons in which the AIS-regional 2{degrees} peak was abolished, a functional perturbation associated with diminished excitability, axonal sprouting and distention of the AIS as assessed by staining for ankyrin-G. Our analysis revealed an additional subpopulation of both axotomized and intact layer 5 pyramidal neurons that manifested a melding together of the AIS- and soma-regional 2{degrees} peaks, suggesting a more subtle aberration of sodium channel function and/or translocation of the AIS initiation zone closer to the soma. When these experiments were repeated in animals in which cyclophilin-D was knocked out, these effects were ameliorated, suggesting that trauma-induced AIS functional perturbation is associated with mitochondrial calcium dysregulation.

neuroscience↗

bioRxiv2021

Best practices for analyzing imputed genotypes from low-pass sequencing in dogs

Although DNA array-based approaches for genome wide association studies (GWAS) permit the collection of thousands of low-cost genotypes, it is often at the expense of resolution and completeness, as SNP chip technologies are ultimately limited by SNPs chosen during array development. An alternative low-cost approach is low-pass whole genome sequencing (WGS) followed by imputation. Rather than relying on high levels of genotype confidence at a set of select loci, low-pass WGS and imputation relies on the combined information from millions of randomly sampled low confidence genotypes. To investigate low-pass WGS and imputation in the dog, we assessed accuracy and performance by downsampling 97 high-coverage (>15x) WGS datasets from 51 different breeds to approximately 1x coverage, simulating low-pass WGS. Using a reference panel of 676 dogs from 91 breeds, genotypes were imputed from the downsampled data and compared to a truth set of genotypes generated from high coverage WGS. Using our truth set, we optimized a variant quality filtering strategy that retained approximately 80% of 14M imputed sites and lowered the imputation error rate from 3.0% to 1.5%. Seven million sites remained with a MAF > 5% and an average imputation quality score of 0.95. Finally, we simulated the impact of imputation errors on outcomes for case-control GWAS, where small effect sizes were most impacted and medium to large effect sizes were minorly impacted. These analyses provide best practice guidelines for study design and data post-processing of low-pass WGS imputed genotypes in dogs.

genomics↗

bioRxiv2021

Multi-omics approach identifies germline regulatory variants associated with hematopoietic malignancies in retriever dog breeds

Histiocytic sarcoma is an aggressive hematopoietic malignancy of mature tissue histiocytes with a poorly understood etiology in humans. A histologically and clinically similar counterpart affects flat-coated retrievers (FCRs) at unusually high frequency, with 20% developing the lethal disease. The similar clinical presentation combined with the closed population structure of dogs, leading to high genetic homogeneity, makes dogs an excellent model for genetic studies of cancer susceptibility. To determine the genetic risk factors underlying histiocytic sarcoma in FCRs, we conducted multiple genome-wide association studies (GWASs), identifying two loci that confer significant risk on canine chromosomes (CFA) 5 (Pwald=4.83x10-9) and 19 (Pwald=2.25x10-7). We subsequently undertook a multi-omics approach that has been largely unexplored in the canine model to interrogate these regions, generating whole genome, transcriptome, and chromatin immunoprecipitation sequencing. These data highlight the PI3K pathway gene PIK3R6 on CFA5, and proximal candidate regulatory variants that are strongly associated with histiocytic sarcoma and predicted to impact transcription factor binding. The CFA5 association colocalizes with susceptibility loci for two hematopoietic malignancies, hemangiosarcoma and B-cell lymphoma, in the closely related golden retriever breed, revealing the risk contribution this single locus makes to multiple hematological cancers. By comparison, the CFA19 locus is unique to the FCR and harbors risk alleles associated with upregulation of TNFAIP6, which itself affects cell migration and metastasis. Together, these loci explain ~35% of disease risk, an exceptionally high value that demonstrates the advantages of domestic dogs for complex trait mapping and genetic studies of cancer susceptibility.

genetics↗

bioRxiv2019

Flavor-specific enhancement of electronic cigarette liquid consumption and preference in mice

BackgroundThe use of electronic cigarettes has increased over the past decade. To determine how the abuse liability of electronic cigarette liquids (e-liquids) differs from nicotine alone, and to determine the impact of flavor, we compared nicotine-containing fruit- and tobacco-flavored e-liquids, and their nicotine-free versions, to nicotine alone in mouse models of oral consumption, reward and aversion. MethodsAdult male C57BL/6J mice voluntarily consumed oral nicotine, equivalent nicotine concentrations of fruit- and tobacco-flavored e-liquid, and equivalent dilutions of the nicotine-free versions in 2-bottle choice tests. Conditioned place preference and place aversion were assessed with peripherally administered e-liquids or nicotine. Serum nicotine and cotinine levels were measured after subcutaneous injections of e-liquid or nicotine. ResultsMice showed higher consumption and preference for the fruit-flavored e-liquid compared with nicotine alone. This increase was not due to the flavor itself as consumption of the nicotine-free fruit-flavored e-liquid was not elevated until the highest concentration tested. The increased consumption and preference were not observed with the tobacco-flavored e-liquid. The conditioned place preference, place aversion and nicotine pharmacokinetics of the fruit-flavored e-liquid were not significantly different from nicotine alone. ConclusionsOur data suggest that fruit, but not tobacco flavor, increased the oral consumption of e-liquid compared with nicotine alone. Moreover, this enhancement was not due to increased consumption of the flavor itself, altered rewarding or aversive properties after peripheral administration, or altered pharmacokinetics. This flavor-specific enhancement suggests that some flavors may lead to higher nicotine intake and increased use of e-liquids compared with nicotine alone. HighlightsO_LIFruit flavor, but not tobacco flavor, enhances e-liquid consumption and preference C_LIO_LIThe nicotine-free flavored e-liquid is not preferred over nicotine alone C_LIO_LIConditioning rewarding and aversive effects are equal between nicotine and e-liquid C_LI

pharmacology and toxicology↗

bioRxiv2019

Higher anhedonia during withdrawal from initial opioid exposure is protective against subsequent opioid self-administration in rats.

Understanding factors contributing to individual differences in vulnerability to opioid addiction is essential for developing more effective preventions and treatments, yet few reliable behavioral predictors of subsequent opioid self-administration have been identified in rodents. Sensitivity to the acute effects of initial drug exposure predicts later addiction vulnerability in both humans and animals, but the relationship of sensitivity to withdrawal from initial drug exposure and later drug use vulnerability is unclear. The goal of the current study was to evaluate whether the degree of anhedonia experienced during withdrawal from early opioid exposure predicts subsequent vulnerability to opioid addiction. Rats were first tested for withdrawal sensitivity following acute injections of morphine (i.e., "acute dependence"), measured as elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior) during naloxone-precipitated and spontaneous withdrawal. Rats were then tested for addiction vulnerability using various measures of i.v. morphine self-administration (MSA) including acquisition, demand, extinction, and reinstatement induced by morphine, stress, and/or drug-associated cues. Greater naloxone-precipitated withdrawal across repeated morphine injections and greater peak spontaneous withdrawal severity following a single morphine injection were associated with lower addiction vulnerability on multiple MSA measures. Withdrawal-induced anhedonia predicted a wider range of MSA measures than did any individual measure of MSA itself. These data suggest that high anhedonia during withdrawal from initial opioid exposure is protective against subsequent opioid addiction vulnerability in rodents, thereby establishing one of the first behavioral measures to predict individual differences in opioid SA. This model promises to be useful for furthering our understanding of behavioral and neurobiological mechanisms underlying vulnerability to opioid addiction.

animal behavior and cognition↗