An altered glial phenotype in the NL3R451C mouse model of autism

Abstract

Autism Spectrum Disorder (ASD; autism) is a neurodevelopmental disorder characterised by deficits in social communication, and restricted and/or repetitive behaviours. While the precise pathophysiologies are unclear, increasing evidence supports a role for dysregulated neuroinflammation in the brain with potential effects on synapse function. Here, we studied characteristics of microglia and astrocytes in the Neuroligin-3 (NL3 R451C) mouse model of autism since these cell types are involved in regulating both immune and synapse function. We observed increased microglial density in the dentate gyrus (DG) of NL3 R451C mice without morphological differences. In contrast, WT and NL3 R451C mice had similar astrocyte density but astrocyte branch length, the number of branch points, as well as cell radius and area were reduced in the DG of NL3 R451C mice. Because retraction of astrocytic processes has been linked to altered synaptic transmission and dendrite formation, we assessed for regional changes in pre-and postsynaptic protein expression in the cortex, striatum and cerebellum in NL3 R451C mice. NL3 R451C mice showed increased striatal postsynaptic density 95 (PSD-95) protein levels and decreased cortical expression of synaptosomal-associated protein 25 (SNAP-25). These changes could contribute to dysregulated neurotransmission and cognition deficits previously reported in these mice. Autism Spectrum Disorder (ASD; autism) is a neurodevelopmental disorder estimated to affect 1 in 54 children 1. Autism is characterised by deficits in social communication, and restricted and/or repetitive patterns of behaviour 2. A complex interaction between genetic and environmental factors is thought to contribute to autism. The clinical heterogeneity and variability in presentation and severity of autism has made diagnosis, treatment and the study of autism-relevant neurobiology challenging 3. However, functional and neuroanatomical abnormalities are consistently reported in autism patients 4-6 , with increasing evidence supporting a role for neuroinflammation in autism pathophysiology 7-9. Neuroinflammation involves the sustained, and often unwarranted, increase in activity of glial cells (i.e. microglia and astrocytes), which release many pro-inflammatory cytokines and chemokines in response to injury, infection or disease. During this activity, 'reactive' microglia and astrocytes show altered morphology. Aberrant neuroimmune profiles have been documented in autism including increased densities of reactive microglia and astrocytes in several brain regions 10-12 accompanied by alterations in cytokine and chemokine secretion in brain tissue 10,13 , cerebrospinal fluid 10,14 and blood 15-17 of autism patients compared to neurotypical controls. In addition to regulating immune function, microglia and astrocytes assist in maintaining synaptic function. Abnormal glial function may therefore influence synaptic circuitry and neuronal connectivity within the central nervous system (CNS) and contribute to regional-specific under-connecti...

Verapamil/Curcumin treatment attenuates the behavioral alterations observed in Williams Syndrome mice by regulation of MAPK pathway and Microglia overexpression

“…Moreover, we also observed an increase in the amount of activated microglia in different brain regions of CD animals, which was prevented by treatment. Interestingly, alterations in activated glia density have also been observed in other mice models for different neurodevelopmental diseases (Lee et al, 2019;Matta et al, 2020). Curcumin has been previously related with the increase of Nrf2 expression and nuclear translocation (Tapia et al, 2012;Fattori et al, 2015), suggesting that this endogenous antiinflammatory pathway is modulating this response in CD animals, which correlates with similar findings in this model (Ortiz-Romero et al, 2018).…”

Neuroligin-3: A Circuit-Specific Synapse Organizer That Shapes Normal Function and Autism Spectrum Disorder-Associated Dysfunction

“…The role of Nlgn1-3 proteins in astrocyte morphogenesis differs in an isoform-and time-dependent manner (Stogsdill et al, 2017). Additionally, the Nlgn3-R451C mutation affects astrocytic morphology by reducing their branch point number, branch length, and territory in the dentate gyrus (Matta et al, 2020). Furthermore, oligodendrocytic Nlgn3 protein contributes to the differentiation of oligodendrocytes (Proctor et al, 2015) and the density of microglia is increased in the dentate gyrus of Nlgn3-R451C KI mice (Matta et al, 2020).…”

“…Additionally, the Nlgn3-R451C mutation affects astrocytic morphology by reducing their branch point number, branch length, and territory in the dentate gyrus (Matta et al, 2020). Furthermore, oligodendrocytic Nlgn3 protein contributes to the differentiation of oligodendrocytes (Proctor et al, 2015) and the density of microglia is increased in the dentate gyrus of Nlgn3-R451C KI mice (Matta et al, 2020). Interestingly, glial progenitor cells from individuals with schizophrenia express significantly lower levels of Nlgn1, Nlgn2, and Nlgn3 mRNA compared with controls (Windrem et al, 2017), suggesting a role for glial Nlgn3 protein in pathophysiological conditions.…”

Astroglia in Autism Spectrum Disorder

“…Codagnone and colleagues (2015) showed that VPA exposed rats, sacrificed at postnatal day 35, have increased glial fibrillary acid protein (GFAP) immunostaining levels in the medial prefrontal cortex and hippocampus, especially in the CA3 subfield. Despite increased GFAP immunoreactivity, which is often associated with pathological processes in the CNS, there are some studies showing changes in the number of GFAP positive cells in VPA and poly (I:C) models [ 93 , 94 , 95 , 96 ], but studies regarding the morphological analysis of glia silhouette in autism are limited [ 11 , 13 ]. Given the still growing knowledge about the pivotal role of those “shape changes” for proper neuronal functioning, a lack of profound morphological analysis of these cells in ASD is quite surprising.…”

“…The differences may be due to the difficulty of accessing human tissue and the inadequate processing of the tissue prior to staining. Disruption in glial markers expression in ASD coincides with pathological changes of neurons within brain structures associated with social behaviour, reward, attention or cognitive processes (i.e., prefrontal cortex, hippocampi, striatum, amygdala, cerebellum) [ 10 , 11 ]. Lack of appropriate support from glia cells may be the cause of neuronal or synaptic connection alterations which may lead to the occurrence of neuropsychiatric disorders such as autism.…”