Transcriptome analysis of microglia in a mouse model of Rett syndrome: differential expression of genes associated with microglia/macrophage activation and cellular stress

Abstract

BackgroundRett syndrome (RTT) is a severe, neurodevelopmental disorder primarily affecting girls, characterized by progressive loss of cognitive, social, and motor skills after a relatively brief period of typical development. It is usually due to de novo loss of function mutations in the X-linked gene, MeCP2, which codes for the gene expression and chromatin regulator, methyl-CpG binding protein 2. Although the behavioral phenotype appears to be primarily due to neuronal Mecp2 deficiency in mice, other cell types, including astrocytes and oligodendrocytes, also appear to contribute to some aspects of the RTT phenotype. In addition, microglia may also play a role. However, the effect of Mecp2 deficiency in microglia on RTT pathogenesis is controversial.MethodsIn the current study, we applied whole transcriptome analysis using RNA-seq to gain insight into molecular pathways in microglia that might be dysregulated during the transition, in female mice heterozygous for an Mecp2-null allele (Mecp2 +/−; Het), from the pre-phenotypic (5 weeks) to the phenotypic phases (24 weeks).ResultsWe found a significant overlap in differentially expressed genes (DEGs) with genes involved in regulating the extracellular matrix, and those that are activated or inhibited when macrophages and microglia are stimulated towards the M1 and M2 activation states. However, the M1- and M2-associated genes were different in the 5- and 24-week samples. In addition, a substantial decrease in the expression of nine members of the heat shock protein (HSP) family was found in the 5-week samples, but not at 24 weeks.ConclusionsThese findings suggest that microglia from pre-phenotypic and phenotypic female mice are activated in a manner different from controls and that pre-phenotypic female mice may have alterations in their capacity to response to heat stress and other stressors that function through the HSP pathway.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-017-0134-z) contains supplementary material, which is available to authorized users.

Microglia from offspring of dams with allergic asthma exhibit epigenomic alterations in genes dysregulated in autism

“…S1C) in our microglial isolations due to the inherent microglial-neuronal interactions including phagocytosis that occur in brain. While our microglia isolations were above the purity of another published microglial transcriptome study (Zhao et al, 2017), we cannot be certain that the higher expression of some of the typically neuronal genes were cell intrinsic to microglia rather than a result of increased neuronal phagocytosis in the MAA brain (Solga et al, 2015), although either explanation is of interest for understanding the pathogenesis. While the function of many of these neurotransmitter receptors on microglia is largely unknown (Schafer et al, 2013), their overall increase in expression following MAA suggests that microglia have altered sensitivity in the juvenile MAA brain.…”

“…MAA DMR associated genes were enriched in MeCP2 target genes identified from high resolution ChIP-sequencing from olfactory epithelium neurons (Rube et al, 2016), suggesting MeCP2 may be associated with sites of MAA differential methylation. MeCP2 has previously been implicated in microglial function in Rett syndrome (Derecki et al, 2012; Cronk et al, 2015; Schafer and Stevens, 2015), and microglia from Rett mouse models show altered gene expression patterns related to glucocorticoid signaling and stress response (Cronk et al, 2015; Zhao et al, 2017). Genes differentially expressed in Rett syndrome mouse model microglia overlapped both MAA differentially expressed and DMR associated genes (Figure 5E and Table S7), further supporting the role for MeCP2 as a reader of DNA methylation in microglia and indicating that MeCP2 function may be negatively impacted in MAA microglia.…”

“…Gene lists and references are listed in Table S7 (Voineagu et al, 2011a; Oskvig et al, 2012; Garbett et al, 2012; Sugathan et al, 2014; Gilissen et al, 2014; Gunawardhana et al, 2014; Gupta et al, 2014; Iossifov et al, 2014b; Cotney et al, 2015; Cronk et al, 2015; Sanders et al, 2015; Holtman et al, 2015; Matcovitch-Natan et al, 2016; Richetto et al, 2016; Rube et al, 2016; Dunaway et al, 2016b; Zhao et al, 2017; Lombardo et al, 2017). For comparisons to differentially expressed genes the background gene list was all genes identified as expressed in the RNAseq experiment (see above description) (14,301 genes).…”

“…D. Gene list overlaps between MAA DE genes, MAA DMR associated genes and MeCP2, FMRP, or CHD8 target genes (Darnell et al, 2011; Sugathan et al, 2014; Cotney et al, 2015; Rube et al, 2016). E. Gene list overlaps between MAA DE genes, MAA DMR associated genes and genes differentially expressed in microglia from Rett syndrome mouse models (Cronk et al, 2015; Zhao et al, 2017). Lists are from MeCP2 −/y null males (fully symptomatic), MeCP2 −/+ heterozygous females at either 5 weeks (prior to symptom onset) or at 24 weeks (fully symptomatic).…”

“…MAA DMR associated genes were enriched in MeCP2 target genes identified from high resolution ChIP sequencing from olfactory epithelium neurons (Rube et al, 2016), suggesting MeCP2 may be associated with sites of MAA differential methylation. MeCP2 has previously been implicated in microglial function in Rett syndrome (Cronk et al, 2015;Derecki et al, 2012;Schafer & Stevens, 2015), and microglia from Rett mouse models show altered gene expression patterns related to glucocorticoid signaling and stress response (Cronk et al, 2015;Zhao et al, 2017).…”