Rett syndrome (RTT), an autism spectrum disorder, is a devastating childhood disorder due to its impact on individuals (1:10,000-15,000 births worldwide), their families and society. RTT is caused by loss-of- function mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2), a transcriptional regulator that binds to methylated CpG sites in promoter regions of DNA. An imbalance of excitatory and inhibitory synaptic function in the hippocampus has been implicated in neurodevelopmental disorders associated with cognitive impairments and mental retardation. Mouse cortical neurons lacking Mecp2 show low levels of neuronal activity caused by an excitation/inhibition imbalance that favors synaptic inhibition, and Mecp2 expression levels modulate excitatory synapse formation between hippocampal neurons. One of the target genes of Mecp2 transcriptional control is Brain-derived neurotrophic factor (Bdnf), a potent modulator of activity-dependent synaptic development, function and plasticity. Considering that BDNF is critical for the maturation of inhibitory GABAergic synapses, and based on our Preliminary Results, our general hypothesis is that impaired development of inhibitory GABAergic synapses due to reduced activity- dependent BDNF release from Mecp2-deficient neurons causes an imbalance of excitatory and inhibitory synaptic function in the hippocampus. We propose the following four Specific Aims: (1) test if the hyperexcitable hippocampal network of neuronal Mecp2 null mice is caused by impaired GABAergic synapse function in area CA3;(2) test whether activity-dependent BDNF release from mossy fibers, the axons of dentate gyrus granule cells, is reduced in neuronal Mecp2 null mice;(3) generate a novel RTT model - dentate granule cell-specific Mecp2 knockout mice - and test whether hippocampal hyperexcitability is associated with impaired activity-dependent BDNF release from granule cell mossy fibers;(4) test if enhancing BDNF expression or mimicking BDNF/TrkB signaling prevents hippocampal hyperexcitability in Mecp2 null mice and dentate granule cell-specific Mecp2 knockout mice. We anticipate that the proposed experiments will yield novel information regarding the consequences of Mecp2 deletion for the excitation/inhibition balance in the hippocampus, uncovering fundamental brain mechanisms involved in the neuropathology of RTT and Autism Spectrum Disorders, and testing an experimental rationale to relieve cognitive impairments and mental retardation in children with associated neurodevelopmental disorders.

Public Health Relevance

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder associated with autism and mental retardation, which is caused by mutations in MECP2, a DNA-binding protein that regulates target genes, including Bdnf. We will test whether impaired development of hippocampal inhibitory synapses due to reduced BDNF release contributes to the excitatory/inhibitory imbalance of synaptic function implicated in cognitive impairments and autism in RTT.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
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Special Emphasis Panel (ZRG1-MDCN-F (02))
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Mamounas, Laura
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University of Alabama Birmingham
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Li, Wei; Bellot-Saez, Alba; Phillips, Mary L et al. (2017) A small-molecule TrkB ligand restores hippocampal synaptic plasticity and object location memory in Rett syndrome mice. Dis Model Mech 10:837-845
Xu, Xin; Garcia, Jordi; Ewalt, Rachel et al. (2017) The BDNF val-66-met Polymorphism Affects Neuronal Morphology and Synaptic Transmission in Cultured Hippocampal Neurons from Rett Syndrome Mice. Front Cell Neurosci 11:203
Carstens, Kelly E; Phillips, Mary L; Pozzo-Miller, Lucas et al. (2016) Perineuronal Nets Suppress Plasticity of Excitatory Synapses on CA2 Pyramidal Neurons. J Neurosci 36:6312-20
Arnold, Miranda; Cross, Rebecca; Singleton, Kaela S et al. (2016) The Endosome Localized Arf-GAP AGAP1 Modulates Dendritic Spine Morphology Downstream of the Neurodevelopmental Disorder Factor Dysbindin. Front Cell Neurosci 10:218
Li, Wei; Xu, Xin; Pozzo-Miller, Lucas (2016) Excitatory synapses are stronger in the hippocampus of Rett syndrome mice due to altered synaptic trafficking of AMPA-type glutamate receptors. Proc Natl Acad Sci U S A 113:E1575-84
Pozzo-Miller, Lucas; Pati, Sandipan; Percy, Alan K (2015) Rett Syndrome: Reaching for Clinical Trials. Neurotherapeutics 12:631-40
Calfa, Gaston; Li, Wei; Rutherford, John M et al. (2015) Excitation/inhibition imbalance and impaired synaptic inhibition in hippocampal area CA3 of Mecp2 knockout mice. Hippocampus 25:159-68
Phillips, Mary; Pozzo-Miller, Lucas (2015) Dendritic spine dysgenesis in autism related disorders. Neurosci Lett 601:30-40
Li, Wei; Pozzo-Miller, Lucas (2014) BDNF deregulation in Rett syndrome. Neuropharmacology 76 Pt C:737-46
Xu, Xin; Kozikowski, Alan P; Pozzo-Miller, Lucas (2014) A selective histone deacetylase-6 inhibitor improves BDNF trafficking in hippocampal neurons from Mecp2 knockout mice: implications for Rett syndrome. Front Cell Neurosci 8:68

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