Philpot Lab - Research and Treatment Strategies for Neurodevelopmental Disorders

 

Identification and validation of novel therapeutics for the treatment of Angelman syndrome


Image 2Our laboratory is determined to identify novel strategies for the treatment of Angelman syndrome.  One approach that we are taking is to activate the paternal copy of the UBE3A allele, which is left intact in the majority of cases of Angelman syndrome but is epigenetically silenced by a long noncoding RNA known as the UBE3A-ATS.  We have previously found that FDA-approved topoisomerase inhibitors can effectively unsilence the paternal copy of UBE3A.  Thus, these inhibitors may have a therapeutic benefit for individuals with Angelman syndrome.  We are studying approaches to effectively and safely deliver topoisomerase inhibitors to the brain.  Additionally, we are assessing the biological role of topoisomerases to understand how topoisomerase inhibitors unsilence paternal UBE3A in neurons and whether they have potential to alleviate Angelman syndrome-like phenotypes in model mice.  Finally, our lab is interested in identifying novel pathways that regulate UBE3A silencing, with the expectation that we can discover how to permanently unsilence paternal UBE3A and provide long-term therapeutic benefits to individuals with Angelman syndrome.


Excitatory/Inhibitory imbalance created by UBE3A dysregulation


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Several Angelman syndrome phenotypes (most notably seizures) may be linked to a disrupted balance between excitatory (E) and inhibitory (I) neurotransmission in the brain.  A major focus of the Philpot laboratory is to genetically parse the molecular, cellular, and circuit components underlying E/I imbalance in Angelman syndrome with the hope of better understanding the etiology of this phenomenon and to perhaps reveal therapeutically tractable targets.  We are currently bringing two novel genetic tools to bear on this problem: 1) conditional maternal Ube3a knockout mice that will enable us to identify the minimal cell types and circuits in which maternal Ube3a deletion leads to E/I imbalance, and 2) conditional Ube3a reinstatement mice in which we will model the efficacy of Ube3a unsilencing therapies toward restoring E/I balance in AS, focusing on critical periods for intervention during development. 



Drug screening to identify Rett syndrome therapeutics 


Image 4Rett syndrome is caused by mutations in gene called MeCP2 on the X chromosome. With a support from the Rett Syndrome Research Trust, our lab aims to identify small molecule compounds that can activate the inactivated MeCP2 gene copy in mice, with the expectation that such compounds represent potential therapeutics for the treatment of Rett syndrome.  Towards this end, we are collaborating with Dr. Bryan Roth (expert in small molecule screening) and Dr. Terry Magnuson (expert in X inactivation) and using robotic fluid handling and high content imaging to perform a a high-throughput neuronal screen for activators of MeCP2 gene expression.  We seek to screen over 25,000 compounds.


Pitt-Hopkins syndrome and other Angelman-like syndromes


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Several single-gene disorders show a striking phenotypic overlap with Angelman syndrome. These include Rett syndrome, Pitt-Hopkins syndrome, chromosome 2q23.1 microdeletion syndrome, and Mowat-Wilson Syndrome. While the genetic basis of each of these disorders is unique, they all share common behavioral deficits, such as intellectual disability, seizures, absent speech, and microcephaly. An aim of the Philpot laboratory is to uncover common and distinct molecular pathways that are regulated by the causative genes associated with these phenotypically similar disorders, which will guide us toward a better understanding of pathogenesis of these disorders as well as inform therapeutic strategies.  For example, Pitt-Hopkins Syndrome (PTHS) is an autism-associated disorder that shares multiple phenotypic characteristics with Angelman syndrome. Until the discovery of the genetic cause of PTHS (haploinsufficiency of the transcription factor 4 gene, TCF4) in 2008, several individuals with PTHS were misdiagnosed with AS. A main focus of the Philpot laboratory is to uncover the molecular mechanisms regulated by TCF4 in the nervous system, with the future aim of designing rationale therapeutics for this devastating disorder. Towards this goal we are currently employing cell biological, molecular, and genetic tools, including two novel mouse models of PTHS.


Techniques employed in the laboratory

Currently our lab is performing the following techniques:

Image 6• In vitro and In vivo whole-cell electrophysiology

• Optogenetics

• RNAseq

• 2-Photon imaging (in collaboration with microscopy core and Spencer Smith’s Lab @ UNC)

• Intrinsic signal optical imaging (with Spencer Smith’s lab)

Image 7• Small molecule screens (in collaboration with Bryan Roth’s lab @ UNC)

• Field potential recordings

• Construction and characterization of knock-in and transgenic mice (with Animal Models Core and Mark Zylka’s lab @ UNC)

• Molecular biology and cell culture

• Pharmacology of synaptic responses

• Immunofluorescence-based laser capture microdissection

• Biochemistry of subcellular fractionation (including PSD purification)

• Immunofluorescence staining

• Behavioral phenotyping (with the core facility run by Sheryl Moy @ UNC)

• Lentiviral knockdown and overexpression of constructs


Positions Available

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