Translational profiling identifies sex-specific metabolic and epigenetic reprogramming of cortical microglia/macrophages in APPPS1-21 mice with an antibiotic-perturbed-microbiome.

BACKGROUND: Microglia, the brain-resident macrophages perform immune surveillance and engage with pathological processes resulting in phenotype changes necessary for maintaining homeostasis. In preceding studies, we showed that antibiotic-induced perturbations of the gut microbiome of APPPS1-21 mice resulted in significant attenuation in Aß amyloidosis and altered microglial phenotypes that are specific to male mice. The molecular events underlying microglial phenotypic transitions remain unclear. Here, by generating 'APPPS1-21-CD11br' reporter mice, we investigated the translational state of microglial/macrophage ribosomes during their phenotypic transition and in a sex-specific manner. METHODS: Six groups of mice that included WT-CD11br, antibiotic (ABX) or vehicle-treated APPPS1-21-CD11br males and females were sacrificed at 7-weeks of age (n = 15/group) and used for immunoprecipitation of microglial/macrophage polysomes from cortical homogenates using anti-FLAG antibody. Liquid chromatography coupled to tandem mass spectrometry and label-free quantification was used to identify newly synthesized peptides isolated from polysomes. RESULTS: We show that ABX-treatment leads to decreased Aß levels in male APPPS1-21-CD11br mice with no significant changes in females. We identified microglial/macrophage polypeptides involved in mitochondrial dysfunction and altered calcium signaling that are associated with Aß-induced oxidative stress. Notably, female mice also showed downregulation of newly-synthesized ribosomal proteins. Furthermore, male mice showed an increase in newly-synthesized polypeptides involved in FcγR-mediated phagocytosis, while females showed an increase in newly-synthesized polypeptides responsible for actin organization associated with microglial activation. Next, we show that ABX-treatment resulted in substantial remodeling of the epigenetic landscape, leading to a metabolic shift that accommodates the increased bioenergetic and biosynthetic demands associated with microglial polarization in a sex-specific manner. While microglia in ABX-treated male mice exhibited a metabolic shift towards a neuroprotective phenotype that promotes Aß clearance, microglia in ABX-treated female mice exhibited loss of energy homeostasis due to persistent mitochondrial dysfunction and impaired lysosomal clearance that was associated with inflammatory phenotypes. CONCLUSIONS: Our studies provide the first snapshot of the translational state of microglial/macrophage cells in a mouse model of Aß amyloidosis that was subject to ABX treatment. ABX-mediated changes resulted in metabolic reprogramming of microglial phenotypes to modulate immune responses and amyloid clearance in a sex-specific manner. This microglial plasticity to support neuro-energetic homeostasis for its function based on sex paves the path for therapeutic modulation of immunometabolism for neurodegeneration.

Spontaneous alloparental care of unrelated offspring by non-breeding Amphiprion ocellaris in absence of the biological parents.

Many species display alloparental care, where individuals care for offspring that are not their own, but usually the behavior is contingent on the individual receiving some direct or indirect benefit. In anemonefish, after removing the breeding male, non-breeders have been observed providing care for eggs they did not sire and which are not kin. Previously this behavior was interpreted as coerced by the female. The purpose of this study was to test the alternative hypothesis that the alloparental care occurs spontaneously without prodding by the female. Groups of Amphiprion ocellaris (male, female and non-breeder) were maintained in the laboratory and behavior monitored after removing the male and both the male and female. Non-breeders began to care for eggs after male removal and further increased parental care after male and female removal. Level of care was not as high as experienced males, but additional experiments showed performance increases with experience. In a separate experiment, non-breeders were placed alone in a novel aquarium and eggs from an established spawning pair were introduced. Approximately 30% of the fish displayed extensive fathering behavior within 90 min. Taken together, our results demonstrate that fathering behavior in A. ocellaris occurs spontaneously, independent of paternity or kinship.

Inhibitory cell populations depend on age, sex, and prior experience across a neural network for Critical Period learning.

In many ways, the complement of cell subtypes determines the information processing that a local brain circuit can perform. For example, the balance of excitatory and inhibitory (E/I) signaling within a brain region contributes to response magnitude and specificity in ways that influence the effectiveness of information processing. An extreme example of response changes to sensory information occur across Critical Periods (CPs). In primary mammalian visual cortex, GAD65 and parvalbumin inhibitory cell types in particular control experience-dependent responses during a CP. Here, we test how the density of GAD65- and parvalbumin-expressing cells may inform on a CP for complex behavioral learning. Juvenile male zebra finch songbirds (females cannot sing) learn to sing through coordinated sensory, sensorimotor, and motor learning processes distributed throughout a well-defined neural network. There is a CP for sensory learning, the process by which a young male forms a memory of his "tutor's" song, which is then used to guide the young bird's emerging song structure. We quantified the effect of sex and experience with a tutor on the cell densities of GAD65- and parvalbumin-expressing cells across major nodes of the song network, using ages that span the CP for tutor song memorization. As a resource, we also include whole-brain mapping data for both genes. Results indicate that inhibitory cell populations differ across sex, age, and experiential conditions, but not always in the ways we predicted.

Striatal transcriptome of a mouse model of ADHD reveals a pattern of synaptic remodeling.

Despite the prevalence and high heritability of Attention-Deficit/Hyperactivity Disorder (ADHD), genetic etiology remains elusive. Clinical evidence points in part to reduced function of the striatum, but which specific genes are differentially expressed and how they sculpt striatal physiology to predispose ADHD are not well understood. As an exploratory tool, a polygenic mouse model of ADHD was recently developed through selective breeding for high home cage activity. Relative to the Control line, the High-Active line displays hyperactivity and motor impulsivity which are ameliorated with amphetamine. This study compared gene expression in the striatum between Control and High-Active mice to develop a coherent hypothesis for how genes might affect striatal physiology and predispose ADHD-like symptoms. To this end, striatal transcriptomes of High-Active and Control mice were analyzed after mice were treated with saline or amphetamines. The pseudogene Gm6180 for n-cofilin (Cfl1) displayed 20-fold higher expression in High-Active mice corresponding with reduced Cfl1 expression suggesting synaptic actin dysregulation. Latrophilin 3 (Lphn3), which is associated with ADHD in human populations and is involved in synapse structure, and its ligand fibronectin leucine rich transmembrane protein 3 (Flrt3), were downregulated in High-Active mice. Multiple genes were altered in High-Active mice in a manner predicted to downregulate the canonical Wnt pathway. A smaller and different set of genes including glyoxalase (Glo1) were differentially regulated in High-Active as compared to Control in response to amphetamine. Together, results suggest genes involved in excitatory synapse regulation and maintenance are downregulated in ADHD-like mice. Consistent with the molecular prediction, stereological analysis of the striatum from a separate set of mice processed for imunohistochemical detection of synaptophysin revealed approximately a 46% reduction in synaptophysin immunoreactivity in High-Active relative to Control. Results provide a new set of molecular targets related to synapse maintenance for the next generation of ADHD medicines.

The impact of maternal neglect on genetic hyperactivity.

Early environmental conditions are increasingly appreciated as critical in shaping behavior and cognition. Evidence suggests that stressful rearing environments can have an enduring impact on behaviors in adulthood, but few studies have explored the possibility that rearing environment could exacerbate genetic hyperactivity disorders. Uncovering a strong environmental influence on the transmission of hyperactivity could provide novel avenues for translational research. Recently we developed a selectively bred High-Active line of mice to model ADHD, providing a unique resource to address the question of environmental transmission. The High-Active line demonstrates transgenerational hyperactivity, but the influence of the postnatal environment (i.e. maternal care provided by dams) on hyperactivity had not been systemically quantified. This study employed a cross-fostering method to simultaneously address 1) whether High-Active and Control pups are provided with similar levels of care in the early environment, and 2) whether any differences in rearing environment influence hyperactive behavior. High-Active dams demonstrated impairment in all measures of maternal competence relative to Controls, which reduced survival rates and significantly reduced the body mass of offspring in early life and at weaning. While the deteriorated postnatal environment provided by High-Active dams was ultimately sufficient to depress Control activity, the hyperactivity of High-Active offspring remained unaffected by fostering condition. These data not only confirm the power of genetics to influence hyperactivity across generations, but also provide evidence that early rearing environments may not have a significant impact on the extreme end of hyperactive phenotypes.

Long-lasting impairments in adult neurogenesis, spatial learning and memory from a standard chemotherapy regimen used to treat breast cancer.

The negative impact of chemotherapy on cognitive function in cancer patients has gained increasing attention in the last decade. Whilst the short-term acute effects on cognition are expected following chemotherapy, the persistence of such impairments in the long-term is still in question. This is despite clinical evidence indicating cognitive difficulties may persist well beyond treatment and affect quality of life. In the present study, we assessed the long-term (3 months) cognitive impact of chemotherapy in a mouse model intended to mimic the human female post-menopausal population receiving chemotherapy for breast cancer. Ovariectomized, female, C57BL/6J mice received two doses of Doxorubicin, Cyclophosphamide, and 5-Fluorouracil or saline vehicle (control), separated by one week. During this interval, mice received BrdU injections to label dividing cells. Results indicate a persistent impairment in learning and recall (1h, 24h and 48h) on the Morris water maze, reduced survival and differentiation of new neurons (BrdU+/NeuN+), and a persistent decline in proliferation of new cells (Ki67(+)) in the dentate gyrus. Locomotor activity, motor performance, and anxiety-like behavior were unaffected. We further evaluated the efficacy of a diet enriched in omega-3-fatty acids (DHA+EPA+DPA), in reversing long-term chemotherapy deficits but no rescue was observed. The model described produces long-term cognitive and cellular impairments from chemotherapy that mimic those observed in humans. It could be useful for identifying mechanisms of action and to test further the ability of lifestyle interventions (e.g., diet) for ameliorating chemotherapy-induced cognitive impairments.