About

Charles A. Hoeffer is an Associate Professor in the Department of Integrative Physiology at the University of Colorado Boulder, affiliated with the Institute for Behavioral Genetics. His research focuses on the regulation of protein synthesis in synaptic plasticity, memory, and neurological disorders. He investigates the regulators of phosphatase function in conditions such as Down syndrome and schizophrenia, and explores the impacts of aging, stress, and neurodegeneration. Hoeffer leads the Molecular Signaling of Neurological Disorders Laboratory, contributing to understanding the molecular mechanisms underlying neurological diseases. He earned his B.S. with Honors in Molecular and Cellular Biology (Biochemistry) from the University of Arizona in 1995 and completed his Ph.D. in Molecular and Cellular Biology (Neuroscience) at the same institution in 2004. His postdoctoral training included work with Dr. Eric Klann at Baylor College of Medicine and New York University. Hoeffer has held various academic and research positions, including adjunct assistant professor at New York University School of Medicine and director of the NYU Rodent Behavior Core. His professional recognition includes awards such as the Whitehead Fellowship Award for Junior Faculty, the Minority New Investigator Award from the Alzheimer's Association, and the Blas Frangione Young Investigator Merit Award.

Research topics

• Neuroscience
• Biology
• Immunology
• Pathology
• Psychology
• Bioinformatics
• Pharmacology
• Medicine
• Genetics

Selected publications

• Restoring RCAN1 dosage mitigates sleep and EEG abnormalities in a Down syndrome model

  Neurobiology of Disease · 2026-04-06

  articleOpen accessSenior author

  BACKGROUND: Approximately 60% of individuals with Down syndrome (DS) have sleep abnormalities independent of breathing obstruction. Previously, we demonstrated increased wakefulness and decreased NREM sleep in the Dp(16)1Yey+ (Dp16) DS model mouse. In this study, we determined if increased RCAN1 levels mediate sleep disruption in Dp16 mice. METHODS: , shortened to Dp16-2N). Approximately equal numbers of male and female mice were used for each age group. We also examined gene expression and anxiety-like behaviors in aged mice. RESULTS: We found that young Dp16 and Dp16-2N mice differ slightly from WT mice in sleep architecture and EEG characteristics. However, with age, more severe sleep deficits manifest in Dp16 mice and are partially rescued by Rcan1 dosage correction. Aged Dp16 mice exhibit significantly less mean EEG total power across different sleep states and activity phases. In contrast, WT and Dp16-2N mice show no age-related differences across states and stages. Aged Dp16 mice diverge from aged WT mice across multiple wake and sleep frequency bands during dark and light phases. In contrast, the EEG characteristics of aged Dp16-2N differ only modestly from those of WT mice. CONCLUSIONS: Combined, our data demonstrate that restoring Rcan1 gene levels mitigates some sleep architecture disruptions and EEG differences observed in aged Dp16 mice.

  PublisherDOI

• Polyserine-mediated targeting of FAF2/UBXD8 ameliorates tau aggregation

  Neuron · 2025-09-02 · 6 citations

  articleOpen access

  Tau aggregation is a hallmark of several neurodegenerative disorders, and the gain of toxic function of misfolded tau species is linked to pathobiology. Herein, we identified proteins that limit tau aggregation when targeted to tau aggregates by polyserine domains. Polyserine targeting was most effective at mitigating tau aggregation when fused to the vasolin-containing protein (VCP) adaptor protein fas-associated factor family member 2/UBX domain-containing protein 8 (FAF2/UBXD8). Surprisingly, FAF2/UBXD8 suppresses tau aggregation independent of VCP but does require ubiquitination, membrane localization, and a ubiquitin regulator X (UBX) domain. Validation in animal models demonstrated that polyserine-targeted FAF2/UBXD8 rescues tau-induced neurodegeneration in Drosophila. Further, delivery of targeted FAF2/UBXD8 reduced gliosis, seeding capacity, and insoluble tau levels in PS19 tau transgenic mice while improving contextual fear conditioning. Collectively, our findings highlight polyserine as a tau-targeting strategy and identify targeted FAF2/UBXD8 as a potent suppressor of tau pathology.

  PublisherDOI

• <scp>AKT2</scp> Modulates Astrocytic Nicotine Responses In Vivo

  Glia · 2025-07-15 · 1 citations

  articleOpen accessSenior authorCorresponding

  A greater understanding of the neurobiology of nicotine is needed to reduce or prevent chronic addiction, ameliorate detrimental nicotine withdrawal effects, and improve cessation rates. Nicotine binds and activates two astrocyte-expressed nicotinic acetylcholine receptors (nAChRs), α4β2 and α7. Protein kinase B-β (Pkb-β or Akt2) expression is restricted to astrocytes in mice and humans and is activated by nicotine. To determine if AKT2 plays a role in astrocytic nicotinic responses, we generated astrocyte-specific Akt2 conditional knockout (cKO) and full Akt2 KO mice. For in/ex vivo studies, we examined mice exposed to chronic nicotine for 2 weeks in drinking water (200 μg/mL) or following acute nicotine challenge (0.09, 0.2 mg/kg) after 24 h. Our in vitro studies used cultured mouse astrocytes to measure nicotine-dependent astrocytic responses. Sholl analysis was used to measure glial fibrillary acidic protein responses in astrocytes. Our data show wild-type (WT) mice exhibit increased astrocyte morphological complexity during acute nicotine exposure, with decreasing complexity during chronic nicotine use, whereas Akt2 cKO mice showed enhanced acute responses and reduced area following chronic exposure. In culture, we found 100 μM nicotine sufficient for morphological changes and blocking α7 or α4β2 nAChRs prevented observed morphological changes. We performed conditioned place preference (CPP) in Akt2 cKO mice, which revealed reduced nicotine preference in cKO mice compared to controls. Finally, we performed RNASeq comparing nicotine- and LPS-mediated gene expression, identifying robust differences between these two astrocytic stimuli. These findings show the importance of nAChRs and AKT2 signaling in the astrocytic response to nicotine.

  PublisherOA PDFDOI

• Multielectrode array characterization of human induced pluripotent stem cell derived neurons in co-culture with primary human astrocytes

  PLoS ONE · 2024-06-25 · 6 citations

  articleOpen accessCorresponding

  Human induced pluripotent stem cells (hiPSCs) derived into neurons offer a powerful in vitro model to study cellular processes. One method to characterize functional network properties of these cells is using multielectrode arrays (MEAs). MEAs can measure the electrophysiological activity of cellular cultures for extended periods of time without disruption. Here we used WTC11 hiPSCs with a doxycycline-inducible neurogenin 2 (NGN2) transgene differentiated into neurons co-cultured with primary human astrocytes. We achieved a synchrony index ∼0.9 in as little as six-weeks with a mean firing rate of ∼13 Hz. Previous reports show that derived 3D brain organoids can take several months to achieve similar strong network burst synchrony. We also used this co-culture to model aspects of blood-brain barrier breakdown by using human serum. Our fully human co-culture achieved strong network burst synchrony in a fraction of the time of previous reports, making it an excellent first pass, high-throughput method for studying network properties and neurodegenerative diseases.

  PublisherOA PDFDOI

• Sleep-wake behavior and responses to sleep deprivation and immune challenge of protein kinase RNA-activated knockout mice

  Brain Behavior and Immunity · 2024-07-21 · 5 citations

  articleOpen access

  Protein Kinase RNA-activated (PKR) is an enzyme that plays a role in many systemic processes, including modulation of inflammation, and is implicated in neurodegenerative diseases, such as Alzheimer’s disease (AD). PKR phosphorylation results in the production of several cytokines involved in the regulation / modulation of sleep, including interleukin-1β, tumor necrosis factor-α and interferon-γ. We hypothesized targeting PKR would alter spontaneous sleep of mice, attenuate responses to sleep deprivation, and inhibit responses to immune challenge. To test these hypotheses, we determined the sleep-wake phenotype of mice lacking PKR (knockout; PKR-/-) during undisturbed baseline conditions; in responses to six hours of sleep deprivation; and after immune challenge with lipopolysaccharide (LPS). Adult male mice (C57BL/6J, n = 7; PKR-/-, n = 7) were surgically instrumented with EEG recording electrodes and an intraperitoneal microchip to record core body temperature. During undisturbed baseline conditions, PKR -/- mice spent more time in non-rapid eye movement sleep (NREMS) and rapid-eye movement sleep (REMS), and less time awake at the beginning of the dark period of the light:dark cycle. Delta power during NREMS, a measure of sleep depth, was less in PKR-/- mice during the dark period, and core body temperatures were lower during the light period. Both mouse strains responded to sleep deprivation with increased NREMS and REMS, although these changes did not differ substantively between strains. The initial increase in delta power during NREMS after sleep deprivation was greater in PKR-/- mice, suggesting a faster buildup of sleep pressure with prolonged waking. Immune challenge with LPS increased NREMS and inhibited REMS to the same extent in both mouse strains, whereas the initial LPS-induced suppression of delta power during NREMS was greater in PKR-/- mice. Because sleep regulatory and immune responsive systems in brain are redundant and overlapping, other mediators and signaling pathways in addition to PKR are involved in the responses to acute sleep deprivation and LPS immune challenge.

  PublisherDOI

• Multielectrode array characterization of human induced pluripotent stem cell derived neurons in co-culture with primary human astrocytes

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-03-08 · 2 citations

  preprintOpen access

  model to study cellular processes. One method to characterize functional network properties of these cells is using multielectrode arrays (MEAs). MEAs can measure the electrophysiological activity of cellular cultures for extended periods of time without disruption. Here we used WTC11 hiPSCs with a doxycycline-inducible neurogenin 2 (NGN2) transgene differentiated into neurons co-cultured with primary human astrocytes. We achieved a synchrony index ~0.9 in as little as six-weeks with a mean firing rate of ~13 Hz. Previous reports show that derived 3D brain organoids can take several months to achieve similar strong network burst synchrony. We also used this co-culture to model aspects of sporadic Alzheimer's disease by mimicking blood-brain barrier breakdown using a human serum. Our fully human co-culture achieved strong network burst synchrony in a fraction of the time of previous reports, making it an excellent first pass, high-throughput method for studying network properties and neurodegenerative diseases.

  PublisherOA PDFDOI

• Polyserine peptides are toxic and exacerbate tau pathology in mice

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-10-12 · 5 citations

  preprintOpen access

  Polyserine domains mediate the association of nuclear RNA binding proteins with cytoplasmic tau aggregates that occurs across tauopathy models and patient samples. In cell lines, polyserine peptides co-localize with and promote formation of tau aggregates suggesting the cytoplasmic mislocalization of polyserine-containing proteins might contribute to human disease. Moreover, polyserine can be produced by repeat associated non-AUG translation in CAG repeat expansion diseases. However, whether polyserine expressed in a mammalian brain is toxic and/or can exacerbate tau pathology is unknown. Here, we used AAV9-mediated delivery to express a 42-repeat polyserine protein in wild-type and tau transgenic mouse models. We observe that polyserine expression has toxic effects in wild-type animals indicated by reduced weight, behavioral abnormalities and a striking loss of Purkinje cells. Moreover, in the presence of a pathogenic variant of human tau, polyserine exacerbates disease markers such as phosphorylated and insoluble tau levels and the seeding capacity of brain extracts. These findings demonstrate that polyserine domains can promote tau-mediated pathology in a mouse model and are consistent with the hypothesis that cytoplasmic mislocalization of polyserine containing proteins might contribute to the progression of human tauopathies.

  PublisherOA PDFDOI

• AKT2 modulates astrocytic nicotine responses <i>in vivo</i>

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-06-01

  preprintOpen accessSenior authorCorresponding

  A greater understanding of the neurobiology of nicotine is needed to reduce or prevent chronic addiction, ameliorate detrimental nicotine withdrawal effects, and improve cessation rates. Nicotine binds and activates two astrocyte-expressed nicotinic acetylcholine receptors (nAChRs), α4β2 and α7. Protein kinase B-β (Pkb-β or Akt2) expression is restricted to astrocytes in mice and humans and is activated by nicotine. To determine if AKT2 plays a role in astrocytic nicotinic responses, we generated astrocyte-specific Akt2 conditional knockout (cKO) and full Akt2 KO mice. For in/ex vivo studies, we examined mice exposed to chronic nicotine for two weeks in drinking water (200 μg/mL) or following acute nicotine challenge (0.09, 0.2 mg/kg) after 24 hrs. Our in vitro studies used cultured mouse astrocytes to measure nicotine-dependent astrocytic responses. Sholl analysis was used to measure glial fibrillary acidic protein responses in astrocytes. Our data show wild-type (WT) mice exhibit increased astrocyte morphological complexity during acute nicotine exposure, with decreasing complexity during chronic nicotine use, whereas Akt2 cKO mice showed enhanced acute responses and reduced area following chronic exposure. In culture, we found 100 μM nicotine sufficient for morphological changes and blocking α7 or α4β2 nAChRs prevented observed morphologic changes. We performed conditioned place preference (CPP) in Akt2 cKO mice, which revealed reduced nicotine preference in cKO mice compared to controls. Finally, we performed RNASeq comparing nicotine- and LPS-mediated gene expression, identifying robust differences between these two astrocytic stimuli. These findings show the importance of nAChRs and AKT2 signaling in the astrocytic response to nicotine.

  PublisherOA PDFDOI

• PKR regulates sleep-wake behavior and its homeostatic responses to sleep deprivation and LPS administration in mice

  Brain Behavior and Immunity · 2023-11-01

  article
  PublisherDOI

• Transcriptome-wide gene-gene interaction associations elucidate pathways and functional enrichment of complex traits

  PLoS Genetics · 2023-05-22 · 9 citations

  articleOpen accessSenior authorCorresponding

  It remains unknown to what extent gene-gene interactions contribute to complex traits. Here, we introduce a new approach using predicted gene expression to perform exhaustive transcriptome-wide interaction studies (TWISs) for multiple traits across all pairs of genes expressed in several tissue types. Using imputed transcriptomes, we simultaneously reduce the computational challenge and improve interpretability and statistical power. We discover (in the UK Biobank) and replicate (in independent cohorts) several interaction associations, and find several hub genes with numerous interactions. We also demonstrate that TWIS can identify novel associated genes because genes with many or strong interactions have smaller single-locus model effect sizes. Finally, we develop a method to test gene set enrichment of TWIS associations (E-TWIS), finding numerous pathways and networks enriched in interaction associations. Epistasis is may be widespread, and our procedure represents a tractable framework for beginning to explore gene interactions and identify novel genomic targets.

  PublisherOA PDFDOI

Recent grants

• NIH Grant F31NS042366

  NIH · $62k

• Sleep Disruption and Alzheimer's Disease Pathology

  NIH · $4.4M · 2019–2024

• Akt regulation of synaptic plasticity and behavior

  NIH · $1.8M · 2015–2021

Frequent coauthors

• Helen Wong

  University of Colorado Boulder

  54 shared

• Eric Klann

  New York Proton Center

  42 shared

• Marissa A. Ehringer

  26 shared

• Josien Levenga

  Horizon Discovery Group (United States)

  24 shared

• Luke M. Evans

  Northern Arizona University

  18 shared

• Curtis Borski

  University of Colorado Boulder

  14 shared

• Jerry A. Stitzel

  University of Colorado System

  13 shared

• Ryan Milstead

  University of Colorado System

  11 shared

Labs

• Molecular Signaling of Neurological Disorders LaboratoryPI

Education

• B.S., Molecular and Cellular Biology (Biochemistry)

  University of Arizona

  1995

• Ph.D., Molecular and Cellular Biology (Neuroscience)

  University of Arizona

  2004

• Other

  Baylor College of Medicine

  2006

• Other

  New York University

  2009

Awards & honors

• National Hispanic Scholarship Fund Finalist (1992)
• Goldwater Scholar Finalist (1993)
• National Science Foundation Minority Pre-doctoral Fellowship…
• ISN Biennial Meeting Young Investigator Award (2009)
• Whitehead Fellowship Award for Junior Faculty (2012)