Biology subjects

Harper, K. M.

Publications and source records attributed to Harper, K. M..

3 recordsLinked to original sources

bioRxiv2023

Sleep disruption precedes forebrain synaptic Tau burden and contributes to cognitive decline in a sex-dependent manner in the P301S Tau transgenic mouse model

BackgroundSleep is an essential process that supports brain health and cognitive function in part through the modification of neuronal synapses. Sleep disruption, and impaired synaptic processes, are common features in neurodegenerative diseases, including Alzheimers disease (AD). However, the casual role of sleep disruption in disease progression is not clear. Neurofibrillary tangles, made from hyperphosphorylated and aggregated Tau protein, form one of the major hallmark pathologies seen in AD and contribute to cognitive decline, synapse loss and neuronal death. Tau has been shown to aggregate in synapses which may impair restorative synapse processes occurring during sleep. However, it remains unclear how sleep disruption and synaptic Tau pathology interact to drive cognitive decline. It is also unclear whether the sexes show differential vulnerability to the effects of sleep loss in the context of neurodegeneration. MethodsWe used a piezoelectric home-cage monitoring system to measure sleep behavior in 3-11month-old transgenic hTau P301S Tauopathy model mice (PS19) and littermate controls of both sexes. Subcellular fractionation and Western blot was used to examine Tau pathology in mouse forebrain synapse fractions. To examine the role of sleep disruption in disease progression, mice were exposed to acute or chronic sleep disruption. The Morris water maze test was used to measure spatial learning and memory performance. ResultsPS19 mice exhibited a selective loss of sleep during the dark phase, referred to as hyperarousal, as an early symptom with an onset of 3months in females and 6months in males. At 6months, forebrain synaptic Tau burden did not correlate with sleep measures and was not affected by acute or chronic sleep disruption. Chronic sleep disruption accelerated the onset of decline of hippocampal spatial memory in PS19 males, but not females. ConclusionsDark phase hyperarousal is an early symptom in PS19 mice that precedes robust Tau aggregation. We find no evidence that sleep disruption is a direct driver of Tau pathology in the forebrain synapse. However, sleep disruption synergized with Tau pathology to accelerate the onset of cognitive decline in males. Despite the finding that hyperarousal appears earlier in females, female cognition was resilient to the effects of sleep disruption.

neuroscience↗

bioRxiv2022

Loss of GABA co-transmission from cholinergic neurons impairs behaviors related to hippocampal, striatal, and medial prefrontal cortex functions

Altered signaling or function of acetylcholine (ACh) has been reported in various neurological diseases, including Alzheimers disease, Tourette syndrome, epilepsy among others. Many neurons that release ACh also co-transmit the neurotransmitter gamma-aminobutyrate (GABA) at synapses in the hippocampus, striatum, and medial prefrontal cortex (mPFC). Although ACh transmission is crucial for higher brain functions such as learning and memory, the role of co-transmitted GABA from ACh neurons in brain function remains unknown. Thus, the overarching goal of this study was to investigate how a systemic loss of GABA co-transmission from ACh neurons affected the behavioral performance of mice. To do this, we used a conditional knock-out mouse of the vesicular GABA transporter (vGAT) crossed with the ChAT-Cre driver line to selectively ablate GABA co-transmission at ACh synapses. In a comprehensive series of standardized behavioral assays, we compared Cre-negative control mice with Cre-positive vGAT knock-out mice of both sexes. Loss of GABA co-transmission from ACh neurons did not disrupt the animals sociability, motor skills or sensation. However, in the absence of GABA co-transmission, we found significant alterations in social, spatial and fear memory as well as a reduced reliance on striatum-dependent response strategies in a T-maze. In addition, male CKO mice showed increased locomotion. Taken together, the loss of GABA co-transmission leads to deficits in higher brain functions and behaviors. Therefore, we propose that ACh/GABA co-transmission modulates neural circuitry involved in the affected behaviors.

neuroscience↗

bioRxiv2021

Early life sleep disruption drives lasting sex-specific changes in behavior in genetically vulnerable Shank3 heterozygous autism model mice

BackgroundPatients with autism spectrum disorder (ASD) experience high rates of sleep disruption beginning early in life, however the developmental consequences of this disruption are not understood. We examined sleep behavior and the consequences of sleep disruption in developing mice bearing C-terminal truncation mutation in the high-confidence ASD risk gene SHANK3 (Shank3{Delta}C). We hypothesized that sleep disruption may be an early sign of developmental divergence, and that clinically-relevant Shank3WT/{Delta}C mice may be at increased risk of lasting deleterious outcomes following early-life sleep disruption. MethodsWe recorded sleep behavior in developing Shank3{Delta}C/{Delta}C, Shank3WT/{Delta}C, and wild type siblings of both sexes using a non-invasive home cage monitoring system. Separately, litters of Shank3WT/{Delta}C and wildtype littermates were exposed to automated mechanical sleep disruption for 7 days prior to weaning (early-life sleep disruption: ELSD) or post-adolescence (PASD) or undisturbed control (CON) conditions. All groups underwent standard behavioral testing as adults. ResultsMale and female Shank3{Delta}C/{Delta}C mice slept significantly less than wild type and Shank3WT/{Delta}C siblings shortly after weaning, with increasing sleep fragmentation in adolescence, indicating that sleep disruption has a developmental onset in this ASD model. ELSD treatment interacted with genetic vulnerability in Shank3WT/{Delta}Cmice, resulting in lasting, sex-specific changes in behavior, whereas wildtype siblings were largely resilient to these effects. Male ELSD Shank3WT/{Delta}Csubjects demonstrated significant changes in sociability, sensory processing, and locomotion, while female ELSD Shank3WT/{Delta}C subjects had a significant reduction in risk aversion. CON Shank3WT/{Delta}C mice, PASD mice, and all wildtype mice demonstrated typical behavioral responses in most tests. LimitationsThis study tested the interaction between developmental sleep disruption and genetic vulnerability using a single ASD mouse model: Shank3{Delta}C (deletion of exon 21). The broader implications of this work should be supported by additional studies using ASD model mice with distinct genetic vulnerabilities. ConclusionOur study shows that sleep disruption during sensitive periods of early life interact with underlying genetic vulnerability to drive lasting and sex-specific changes in behavior. As individuals progress through maturation they gain resilience to the lasting effects of sleep disruption. This work highlights developmental sleep disruption as an important vulnerability in ASD susceptibility.

animal behavior and cognition↗