Abnormal Microglia and Enhanced Inflammation-Related Gene Transcription in Mice with Conditional Deletion ofCtcfinCamk2a-Cre-Expressing Neurons

Abstract

CCCTC-binding factor (CTCF) is an 11 zinc finger DNA-binding domain protein that regulates gene expression by modifying 3D chromatin structure. Human mutations in cause intellectual disability and autistic features. Knocking out in mouse embryonic neurons is lethal by neonatal age, but the effects of CTCF deficiency in postnatal neurons are less well studied. We knocked out postnatally in glutamatergic forebrain neurons under the control of ; ( CKO) mice of both sexes were viable and exhibited profound deficits in spatial learning/memory, impaired motor coordination, and decreased sociability by 4 months of age. CKO mice also had reduced dendritic spine density in the hippocampus and cerebral cortex. Microarray analysis of mRNA from CKO mouse hippocampus identified increased transcription of inflammation-related genes linked to microglia. Separate microarray analysis of mRNA isolated specifically from CKO mouse hippocampal neurons by ribosomal affinity purification identified upregulation of chemokine signaling genes, suggesting crosstalk between neurons and microglia in CKO hippocampus. Finally, we found that microglia in CKO mouse hippocampus had abnormal morphology by Sholl analysis and increased immunostaining for CD68, a marker of microglial activation. Our findings confirm that KO in postnatal neurons causes a neurobehavioral phenotype in mice and provide novel evidence that CTCF depletion leads to overexpression of inflammation-related genes and microglial dysfunction. CCCTC-binding factor (CTCF) is a DNA-binding protein that organizes nuclear chromatin topology. Mutations in cause intellectual disability and autistic features in humans. CTCF deficiency in embryonic neurons is lethal in mice, but mice with postnatal CTCF depletion are less well studied. We find that mice lacking in -expressing neurons ( CKO mice) have spatial learning/memory deficits, impaired fine motor skills, subtly altered social interactions, and decreased dendritic spine density. We demonstrate that CKO mice overexpress inflammation-related genes in the brain and have microglia with abnormal morphology that label positive for CD68, a marker of microglial activation. Our findings suggest that inflammation and dysfunctional neuron-microglia interactions are factors in the pathology of CTCF deficiency.

Depletion of regulatory T cells increases T cell brain infiltration, reactive astrogliosis, and interferon-γ gene expression in acute experimental traumatic brain injury

“…e IgG levels in ipsilesional brain tissues from DEREG and WT mice were not significantly (ns) different (Fig. 4e, p = 0.063, oneway ANOVA followed by Tukey's multiple comparison test) expression of inflammation-related genes either in response to environmental factors [65] or to genetic factors [66]. Along with the observation of increased IFN-γ expression, our results from the rotarod performance test indicate that the depletion of Tregs causes transient aggravation of motor deficits at 1 dpi.…”

CCL17 exerts a neuroimmune modulatory function and is expressed in hippocampal neurons

“…Intriguingly, both chemokines were also found to be elevated in patients with autism spectrum disorders (AL-Ayadhi & Mostafa, 2013). In line, during the revision of this article, a study was published showing that conditional ablation of the CCCTC-binding factor (CTCF) in Camk2a-expressing neurons led to increased expression of Ccl17 in hippocampal neurons, accompanied by elevated proportions and altered morphology of microglia in the hippocampus, and behavioral deficiencies of the mice in spatial learning and memory (McGill et al, 2018). Furthermore, a recent study by Shen et al reported that repeated LPS stimulation in postnatal mice caused a higher susceptibility to epileptic seizures depending on TLR4 expression and MyD88 signaling in astrocytes, whereas LPS stimulation in later life mainly activated microglia but did not increase the incidence of epileptic seizures (Shen et al, 2016).…”

Epigenomic convergence of genetic and immune risk factors in neurodevelopmental disorder cortex

“…For example, multiple studies in mouse Mecp2 mutant models of Rett syndrome show evidence of microglial activation and involvement in disease progression (Derecki et al 2012;Cronk et al 2015;Horiuchi et al 2016). In addition, conditional deletion of CCCTC binding factor (CTCF) specifically in postnatal glutamatergic forebrain neurons in mice decreased neuronal dendritic spine density, and microglia in these animals adopt an abnormal morphology and up-regulate transcription of microglial inflammatory genes (Mcgill et al 2017). Therefore, immune signatures observed across transcriptomic and epigenomic studies in human ASD brain may be partially driven by an immune response to abnormal neuronal processes that arise from genetic and epigenetic etiologies.…”