Astrocyte Transcriptome from the Mecp2308-Truncated Mouse Model of Rett Syndrome

Abstract

Mutations in the gene encoding the transcriptional modulator methyl-CpG binding protein 2 (MeCP2) are responsible for the neurodevelopmental disorder Rett syndrome which is one of the most frequent sources of intellectual disability in women. Recent studies showed that loss of Mecp2 in astrocytes contributes to Rett-like symptoms and restoration of Mecp2 can rescue some of these defects. The goal of this work is to compare gene expression profiles of wild-type and mutant astrocytes from Mecp2(308/y) mice (B6.129S-MeCP2<tm1Heto>/J) by using Affymetrix mouse 2.0 microarrays. Results were confirmed by quantitative real-time RT-PCR and by Western blot analysis. Gene set enrichment analysis utilizing Ingenuity Pathways was employed to identify pathways disrupted by Mecp2 deficiency. A total of 2152 genes were statistically differentially expressed between wild-type and mutated samples, including 1784 coding transcripts. However, only 257 showed fold changes >1.2. We confirmed our data by replicative studies in independent primary cultures of cortical astrocytes from Mecp2-deficient mice. Interestingly, two genes known to encode secreted proteins, chromogranin B and lipocalin-2, showed significant dysregulation. These proteins secreted from Mecp2-deficient glia may exert negative non-cell autonomous effects on neuronal properties, including dendritic morphology. Moreover, transcriptional profiling revealed altered Nr2f2 expression which may explain down- and upregulation of several target genes in astrocytes such as Ccl2, Lcn2 and Chgb. Unraveling Nr2f2 involvement in Mecp2-deficient astrocytes could pave the way for a better understanding of Rett syndrome pathophysiology and offers new therapeutic perspectives.

Genome‐wide transcriptomic and proteomic studies of Rett syndrome mouse models identify common signaling pathways and cellular functions as potential therapeutic targets

“…Most studies were conducted in males, with two exclusively in females (Bedogni et al, ; Zhao et al, ), and one study using both genders (Johnson et al, ). The studies were mostly carried out using knockout mice (null), with a small proportion in Mecp2 ‐knock in mice ( Mecp 2 R270X , Mecp 2 G273X , Mecp 2 308 , Mecp 2 T158A‐Tavi , and Mecp 2 R106W‐Tavi ) (Baker et al, ; Delepine et al, ; Gabel et al, ; Johnson et al, ), and Mecp2 overexpressing mice (Tg) (Ben‐Shachar, Chahrour, Thaller, Shaw, & Zoghbi, ; Chahrour et al, ; Chen et al, ; Samaco et al, ).…”

“…Two studies used a combination of four distinct neuronal cell populations including thick tufted pyramidal neurons from the motor cortex, fast‐spiking parvalbumin‐positive interneurons from the motor cortex, noradrenergic locus coeruleus neurons, and cerebellar Purkinje cells (Ehrhart et al, ; Sugino et al, ). Other studies used astrocytes (Delepine et al, ; Yasui et al, ) and microglia and peritoneal macrophages (Cronk et al, ), while others used cardiovascular progenitor cells (Hara et al, ) and cortical callosal projection neurons (Kishi et al, ). Studies using cell sources not originating from brain regions include the use of fibroblasts (Orlic‐Milacic et al, ), skeletal muscle (Gold et al, ), and blood (Sanfeliu et al, ).…”

“…Although the Rett phenotype is predominantly due to neuronal Mecp2 deficiency, astrocytes and microglia play a significant role in the pathogenesis of Rett syndrome (Sharma, Singh, Frost, & Pillai, ). Transcriptomic profiling of astrocytes cultured from early postnatal pups identified differentially expressed genes enriched in astrocyte signaling, neuronal support and function (Yasui et al, ), as well as glutamate receptor signaling and cytokine signaling (Delepine et al, ). In addition, microglia cultured from whole brains of female heterozygous Mecp2 ‐null mice at 5 week‐old with no phenotypic symptoms, and 24 weeks with apparent phenotypic symptoms, revealed many dysregulated genes involved in the activation of macrophages, heat shock protein family genes, and genes regulated by NK‐κB in response to TNF (Zhao et al, ).…”

Profiles of gene expression in the hippocampal formation of rats with experimentally‐induced brain dysplasia

“…In particular, Nr2f2 signaling is capable of repressing parvalbumin‐expressing interneuron fate specification (Hu et al, ), which is in agreement with deficits often being found in this specific population in humans, in the form of cell loss (Zamecnik et al, ) or ectopic overabundance (Kuchukhidze et al, ). There is also the possibility of other cellular populations being affected by Nr2f2 dysregulation, as this factor has also recently been identified in astrocytes from methyl‐CpG binding protein 2 ( Mecp2 ) deficient mice, a model of Rett's syndrome (Delépine et al, ). On a similar note, Rfx3 ‐deficient mice belong to a family of animal models of primary ciliopathies, resulting in agenesis of the corpus callosum, albeit with only partial penetrance, which is intriguingly similar to the frequency of such abnormalities reported by our group previously in rats irradiated at E13 (Edwards et al, ; Kielbinski et al, ).…”

Roles of Methyl-CpG Binding Protein 2 in Immune Function

“…Multiple groups have performed transcriptome-level analysis of astrocytes from mouse models of Rett syndrome, finding significant changes in gene expression (Delepine et al, 2015;Yasui et al, 2013), and confirming Mecp2 binding to the promoters of predicted target genes via chromatin immunoprecipitation (ChIP)-seq (Yasui et al, 2013). It was also demonstrated that Mecp2-null astrocytes have abnormal glutamate clearance (Okabe et al, 2012), a finding that has also been observed in Mecp2-null microglia (Maezawa and Jin, 2010), and which may have direct effects on neurons.…”