Megalocephaly (or MEG) is a developmental brain disorder characterized by generalized brain overgrowth. It occurs in a growing number of developmental and metabolic disorders and is associated with severe childhood neurological complications including epilepsy, intellectual disability, autism, and hydrocephalus and Chiari malformations. MEG shows significant overlap with more severe but segmental brain disorders including hemimegalencephaly (HMEG) and focal cortical dysplasia (FCD) that collectively constitute the most common cause of intractable epilepsy in children. Activating mutations in key genes within the critical PI3K- AKT-mTOR signaling network (including PIK3CA, PIK3R2, AKT3 and CCND2) have been recently identified in MEG, HMEG and FCD, suggesting that these phenotypes constitute a single broad spectrum of developmental brain disorders with shared molecular etiologies and neuropathological features. The goal of this proposal is to interrogate the molecular basis of these disorders in affected human-derived cells and tissues to define the mutational spectrum, levels of mosaicism, tissue distribution and pathway dysregulation in these disorders. First, I propose to perform single cell sequencing of affected neurons from HMEG and FCD human brain samples obtained from epilepsy surgery to test for known and candidate genes. Second, I will globally assay PI3K-AKT pathway proteins in affected human brain tissues with mutations in key PI3K-AKT pathway genes using high throughput proteomics to identify pathway dysregulation and localize specific sub-pathways and downstream targets. Third, the PI3K AKT genes discovered so far explain ~75% of children with the two most common MEG syndromes, ~25% with HMEG-FCD and none with rare MEG syndromes. I propose studies to identify additional MEG-HMEG-FCD causative genes using whole exome and whole genome sequencing on multiple tissues from affected individuals. My career goal is to become a physician-scientist devoted to integrating cutting-edge genomic and proteomic techniques on human-derived brain tissues, including single cell sequencing, with accurate and quantitative phenotyping to further our understanding of the molecular and biologic basis of human developmental brain disorders. I propose a five-year research program that will incorporate didactic and research training under the mentorship of Dr. William B. Dobyns at the Center for Integrative Brain Research (CIBR). My advisory committee and network of collaborators, combined with the resources at the Seattle Children's Research Institute and University of Washington, will provide the environment necessary for my successful completion of this proposal and transition to an independently funded physician-scientist.

Public Health Relevance

Developmental disorders causing an abnormally large brain size (or 'megalocephaly'), and more severe but focal brain malformations including hemimegalencephaly and focal cortical dysplasia, are common in the pediatric population and are associated with significant neurologic complications including intellectual disability, epileps, autism, hydrocephalus, and Chiari malformations, among others. Recent advances in genomic technologies identified mutations of the same genes in these syndromes, which all belong to the important PI3K-AKT signaling pathway. The goal of this project is to interrogate the molecular basis of these disorders on cell- and tissue-specific levels using a variety of complementary techniques, which will substantially improve our understanding of the biologic basis of these phenotypes, facilitate the development of new diagnostic tests, and lead to the identification of future gene- and pathway-based therapeutic targets.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08NS092898-02
Application #
9112033
Study Section
NST-2 Subcommittee (NST)
Program Officer
Riddle, Robert D
Project Start
2015-08-01
Project End
2020-05-31
Budget Start
2016-06-01
Budget End
2017-05-31
Support Year
2
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Seattle Children's Hospital
Department
Type
DUNS #
048682157
City
Seattle
State
WA
Country
United States
Zip Code
98101
Dobyns, William B; Aldinger, Kimberly A; Ishak, Gisele E et al. (2018) MACF1 Mutations Encoding Highly Conserved Zinc-Binding Residues of the GAR Domain Cause Defects in Neuronal Migration and Axon Guidance. Am J Hum Genet 103:1009-1021
Fry, Andrew E; Fawcett, Katherine A; Zelnik, Nathanel et al. (2018) De novo mutations in GRIN1 cause extensive bilateral polymicrogyria. Brain :
Bozarth, Xiuhua; Dines, Jennifer N; Cong, Qian et al. (2018) Expanding clinical phenotype in CACNA1C related disorders: From neonatal onset severe epileptic encephalopathy to late-onset epilepsy. Am J Med Genet A 176:2733-2739
Marcogliese, Paul C; Shashi, Vandana; Spillmann, Rebecca C et al. (2018) IRF2BPL Is Associated with Neurological Phenotypes. Am J Hum Genet 103:245-260
Shukla, Anju; Saneto, Russell P; Hebbar, Malavika et al. (2018) A neurodegenerative mitochondrial disease phenotype due to biallelic loss-of-function variants in PNPLA8 encoding calcium-independent phospholipase A2?. Am J Med Genet A 176:1232-1237
Ruggeri, Gaia; Timms, Andrew E; Cheng, Chi et al. (2018) Bi-allelic mutations of CCDC88C are a rare cause of severe congenital hydrocephalus. Am J Med Genet A 176:676-681
Piacitelli, Andrew M; Jensen, Dana M; Brandling-Bennett, Heather et al. (2018) Characterization of a severe case of PIK3CA-related overgrowth at autopsy by droplet digital polymerase chain reaction and report of PIK3CA sequencing in 22 patients. Am J Med Genet A 176:2301-2308
Di Donato, Nataliya; Timms, Andrew E; Aldinger, Kimberly A et al. (2018) Analysis of 17 genes detects mutations in 81% of 811 patients with lissencephaly. Genet Med 20:1354-1364
Tripathy, Ratna; Leca, Ines; van Dijk, Tessa et al. (2018) Mutations in MAST1 Cause Mega-Corpus-Callosum Syndrome with Cerebellar Hypoplasia and Cortical Malformations. Neuron :
Martinelli, Simone; Krumbach, Oliver H F; Pantaleoni, Francesca et al. (2018) Functional Dysregulation of CDC42 Causes Diverse Developmental Phenotypes. Am J Hum Genet 102:309-320

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