Drosophila as a Model for MECP2 Gain of Function in Neurons

Abstract

Methyl-CpG-binding protein 2 (MECP2) is a multi-functional regulator of gene expression. In humans loss of MECP2 function causes classic Rett syndrome, but gain of MECP2 function also causes mental retardation. Although mouse models provide valuable insight into Mecp2 gain and loss of function, the identification of MECP2 genetic targets and interactors remains time intensive and complicated. This study takes a step toward utilizing Drosophila as a model to identify genetic targets and cellular consequences of MECP2 gain-of function mutations in neurons, the principle cell type affected in patients with Rett-related mental retardation. We show that heterologous expression of human MECP2 in Drosophila motoneurons causes distinct defects in dendritic structure and motor behavior, as reported with MECP2 gain of function in humans and mice. Multiple lines of evidence suggest that these defects arise from specific MECP2 function. First, neurons with MECP2-induced dendrite loss show normal membrane currents. Second, dendritic phenotypes require an intact methyl-CpG-binding domain. Third, dendritic defects are amended by reducing the dose of the chromatin remodeling protein, osa, indicating that MECP2 may act via chromatin remodeling in Drosophila. MECP2-induced motoneuron dendritic defects cause specific motor behavior defects that are easy to score in genetic screening. In sum, our data show that some aspects of MECP2 function can be studied in the Drosophila model, thus expanding the repertoire of genetic reagents that can be used to unravel specific neural functions of MECP2. However, additional genes and signaling pathways identified through such approaches in Drosophila will require careful validation in the mouse model.

Mutations in KATNB1 Cause Complex Cerebral Malformations by Disrupting Asymmetrically Dividing Neural Progenitors

“…8C–D). Because dendritic defects in flight motoneurons alter flight performance (Vonhoff et al, 2012), we tested flight ability and found a significantly reduced flight response in adult D42> kat80 - IR versus wild type flies (Fig. 8F).…”

Temporal coherency between receptor expression, neural activity and AP-1-dependent transcription regulatesDrosophilamotoneuron dendrite development

“…Drosophila melanogaster were reared as previously described (Vonhoff and Duch, 2010;Vonhoff et al, 2012). Motoneuron GAL4 driver lines were: (1) w; P103.3-GAL4, UAS-mCD8-GFP;+, (2) C380-GAL4, UAS-mCD8-GFP;; Cha-GAL80 and (3) w;UAS-mCD8-GFP; D42-GAL4, Cha-GAL80.…”

MECP2 impairs neuronal structure by regulating KIBRA

“…UAS-hMECP2 and UAS-hR106W transgenic flies (Cukier et al, 2008; Vonhoff et al, 2012) were kindly provided by Dr. J Botas (Baylor College of Medicine, Houston, Texas). UAS-kibraRNAi on the X chromosome (Genevet et al, 2010) was obtained from the Vienna Drosophila Resource Center.…”

“…In patients and in mouse models both MECP2 loss- and gain- of function can cause changes in dendritic morphology (Armstrong, 2005; Cheng et al, 2014; Wang et al, 2013; Zhou et al, 2006). While there is no MECP2 ortholog in Drosophila , we recently found that expression of human MECP2 (h MECP2 ) severely reduces the dendritic complexity of identified Drosophila motoneurons while maintaining normal membrane currents (Vonhoff et al, 2012). …”

“…Further, other proteins with methyl binding domains (MBD) exist in Drosophila , and many MECP2 interactors, including other parts of the chromatin modifying machinery, have well conserved orthologs (Hendrich and Tweedie, 2003). When expressed in Drosophila , h MECP2 associates with chromatin, can be modified by orthologs of known interacting proteins, and, like in mammals, is phosphorylated at serine 423 (Cukier et al, 2008), and causes specific defects in dendritic morphology (Vonhoff et al, 2012). Furthermore, as observed in humans and mouse models (Collins et al, 2004; Ramocki et al, 2010; Van Esch, 2011), hMECP2 expression in Drosophila causes impairments in motor behavior (Cukier et al, 2008; Vonhoff et al, 2012).…”