title: Haploinsufficiency of BAZ1B contributes to Williams syndrome through transcriptional dysregulation of neurodevelopmental pathways.
abstract: Williams syndrome (WS) is a neurodevelopmental disorder caused by a genomic deletion of ∼28 genes that results in a cognitive and behavioral profile marked by overall intellectual impairment with relative strength in expressive language and hypersocial behavior. Advancements in protocols for neuron differentiation from induced pluripotent stem cells allowed us to elucidate the molecular circuitry underpinning the ontogeny of WS. In patient-derived stem cells and neurons, we determined the expression profile of the Williams-Beuren syndrome critical region-deleted genes and the genome-wide transcriptional consequences of the hemizygous genomic microdeletion at chromosome 7q11.23. Derived neurons displayed disease-relevant hallmarks and indicated novel aberrant pathways in WS neurons including over-activated Wnt signaling accompanying an incomplete neurogenic commitment. We show that haploinsufficiency of the ATP-dependent chromatin remodeler, BAZ1B, which is deleted in WS, significantly contributes to this differentiation defect. Chromatin-immunoprecipitation (ChIP-seq) revealed BAZ1B target gene functions are enriched for neurogenesis, neuron differentiation and disease-relevant phenotypes. BAZ1B haploinsufficiency caused widespread gene expression changes in neural progenitor cells, and together with BAZ1B ChIP-seq target genes, explained 42% of the transcriptional dysregulation in WS neurons. BAZ1B contributes to regulating the balance between neural precursor self-renewal and differentiation and the differentiation defect caused by BAZ1B haploinsufficiency can be rescued by mitigating over-active Wnt signaling in neural stem cells. Altogether, these results reveal a pivotal role for BAZ1B in neurodevelopment and implicate its haploinsufficiency as a likely contributor to the neurological phenotypes in WS.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute, Biomolecular Science and Engineering Program.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Lalli
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Jang
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Joo-Hye C
authors.initials: JH
authors.lastname: Park
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Yidi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Elmer
authors.initials: E
authors.lastname: Guzman
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Morgane
authors.initials: M
authors.lastname: Audouard
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute, Department of Physics, University of California, Santa Barbara, CA, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bridges
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Tovar
authors.affiliation: Victor Babes National Institute of Pathology, Clinical Cytogenetics, Bucharest, Romania.
authors.forename: Sorina M
authors.initials: SM
authors.lastname: Papuc
authors.affiliation: Victor Babes National Institute of Pathology, Clinical Cytogenetics, Bucharest, Romania.
authors.forename: Andreea C
authors.initials: AC
authors.lastname: Tutulan-Cunita
authors.affiliation: Gladstone Institute of Neurological Disease, University of California, San Francisco, CA, USA and.
authors.forename: Yadong
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Victor Babes National Institute of Pathology, Clinical Cytogenetics, Bucharest, Romania, Alexandru Obregia Clinical Hospital of Psychiatry, Neuropediatric Pathology, Bucharest, Romania.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Budisteanu
authors.affiliation: Victor Babes National Institute of Pathology, Clinical Cytogenetics, Bucharest, Romania.
authors.forename: Aurora
authors.initials: A
authors.lastname: Arghir
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Neuroscience Research Institute, Biomolecular Science and Engineering Program, kosik@lifesci.ucsb.edu.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Kosik
mesh_terms: D002872:Chromosome Deletion; D002897:Chromosomes, Human, Pair 7; D005260:Female; D018507:Gene Expression Regulation, Developmental; D057895:Haploinsufficiency; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism* / Q000502:physiology; D055495:Neurogenesis; D009474:Neurons / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D059467:Transcriptome; D018980:Williams Syndrome / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D000092468:Bromodomain Containing Proteins
chemical_list: D014157:Transcription Factors; C116750:BAZ1B protein, human; D000092468:Bromodomain Containing Proteins