Astrocyte-specific regulation of hMeCP2 expression in Drosophila

Abstract

Alterations in the expression of Methyl-CpG-binding protein 2 (MeCP2) either by mutations or gene duplication leads to a wide spectrum of neurodevelopmental disorders including Rett Syndrome and MeCP2 duplication disorder. Common features of Rett Syndrome (RTT), MeCP2 duplication disorder, and neuropsychiatric disorders indicate that even moderate changes in MeCP2 protein levels result in functional and structural cell abnormalities. In this study, we investigated two areas of MeCP2 pathophysiology using Drosophila as a model system: the effects of MeCP2 glial gain-of-function activity on circuits controlling sleep behavior, and the cell-type specific regulation of MeCP2 expression. In this study, we first examined the effects of elevated MeCP2 levels on microcircuits by expressing human MeCP2 (hMeCP2) in astrocytes and distinct subsets of amine neurons including dopamine and octopamine (OA) neurons. Depending on the cell-type, hMeCP2 expression reduced sleep levels, altered daytime/nighttime sleep patterns, and generated sleep maintenance deficits. Second, we identified a 498 base pair region of the MeCP2e2 isoform that is targeted for regulation in distinct subsets of astrocytes. Levels of the full-length hMeCP2e2 and mutant RTT R106W protein decreased in astrocytes in a temporally and spatially regulated manner. In contrast, expression of the deletion Δ166 hMeCP2 protein was not altered in the entire astrocyte population. qPCR experiments revealed a reduction in full-length hMeCP2e2 transcript levels suggesting transgenic hMeCP2 expression is regulated at the transcriptional level. Given the phenotypic complexities that are caused by alterations in MeCP2 levels, our results provide insight into distinct cellular mechanisms that control MeCP2 expression and link microcircuit abnormalities with defined behavioral deficits.

Drosophila Glia: Models for Human Neurodevelopmental and Neurodegenerative Disorders

“…Interestingly, astrocyte-specific MECP2 overexpression in Drosophila causes a reduction in the total time spent asleep and induces deficits in sleep maintenance. Defects in sleep behavior are neuropsychological features of RETT, suggesting that abnormal sleep patterns might be caused by MECP2 overexpression in astrocytes [ 139 ]. Through Drosophila disease models, it has been revealed that the ectopic expression of MECP2 induces deficits in neuronal development and behavior, which is regulated by glial cells, especially astrocytes.…”

Sleep problems in Rett syndrome animal models: A systematic review

“…Thirteen studies were identified by this systematic search as summarized in Table 1. We categorized the studies into three groups according to the species of animal used for modeling RTT, which were one on cynomolgus monkey (Y. Chen et al., 2017), two on Drosophila (Gupta, Morgan, Bailey, & Certel, 2016; Hess‐Homeier, Fan, Gupta, Chiang, & Certel, 2014), and 10 using mice (D'Cruz et al., 2010; Fuchs et al., 2018; Johnston et al., 2014; Li et al., 2015; Lo Martire et al., 2017; Moretti, Bouwknecht, Teague, Paylor, & Zoghbi, 2005; Ren, Ding, Funk, & Greer, 2012; Robinson, Plano, Cobb, & Riedel, 2013; Tsuchiya et al., 2015; Wither et al., 2012).…”

“…Drosophila (Gupta, Morgan, Bailey, & Certel, 2016;Hess-Homeier, Fan, Gupta, Chiang, & Certel, 2014), and 10 using mice (D'Cruz et al, 2010;Fuchs et al, 2018;Johnston et al, 2014;Li et al, 2015;Lo Martire et al, 2017;Moretti, Bouwknecht, Teague, Paylor, & Zoghbi, 2005;Ren, Ding, Funk, & Greer, 2012;Robinson, Plano, Cobb, & Riedel, 2013;Tsuchiya et al, 2015;Wither et al, 2012).…”

Functional conservation of MBD proteins: MeCP2 and Drosophila MBD proteins alter sleep

“…In a similar manner, hMeCP2 expression in 5-HT neurons also results in a loss of nighttime sleep, however, with the fine temporal resolution, we can identify sleep loss intervals that are both unique and overlapping when compared to hMeCP2 expression in OA neurons. Finally, in a previous study we determined that hMeCP2 expression in astrocytes non-cell-autonomously alters the sleep network only during distinct nighttime hours (Hess-Homeier et al 2014).…”

“…Total RNA from each pool (∼35 heads/pool) was isolated by Tri-Reagent (Molecular Research Center, Cincinnati, OH, USA). The RNA samples were DNase treated and reverse transcribed as described previously (Hess-Homeier et al 2014). The qPCR reactions were carried out in quadruplicate for each gene and genotype on an Agilent Stratagene Mx3005P platform using following thermal protocol: 95 ∘ C -10 min; 40 × (95 ∘ C -30 seconds; 53 ∘ C -1 min; 72 ∘ C -1 min) followed by 0.5 ∘ C stepwise increment from 65 to 95 ∘ C. Cyclin-dependent kinase 2 (Cdc2c) reference gene was used for data normalization.…”