Haploinsufficiency for Core Exon Junction Complex Components Disrupts Embryonic Neurogenesis and Causes p53-Mediated Microcephaly.

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2016-09

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Abstract

The exon junction complex (EJC) is an RNA binding complex comprised of the core components Magoh, Rbm8a, and Eif4a3. Human mutations in EJC components cause neurodevelopmental pathologies. Further, mice heterozygous for either Magoh or Rbm8a exhibit aberrant neurogenesis and microcephaly. Yet despite the requirement of these genes for neurodevelopment, the pathogenic mechanisms linking EJC dysfunction to microcephaly remain poorly understood. Here we employ mouse genetics, transcriptomic and proteomic analyses to demonstrate that haploinsufficiency for each of the 3 core EJC components causes microcephaly via converging regulation of p53 signaling. Using a new conditional allele, we first show that Eif4a3 haploinsufficiency phenocopies aberrant neurogenesis and microcephaly of Magoh and Rbm8a mutant mice. Transcriptomic and proteomic analyses of embryonic brains at the onset of neurogenesis identifies common pathways altered in each of the 3 EJC mutants, including ribosome, proteasome, and p53 signaling components. We further demonstrate all 3 mutants exhibit defective splicing of RNA regulatory proteins, implying an EJC dependent RNA regulatory network that fine-tunes gene expression. Finally, we show that genetic ablation of one downstream pathway, p53, significantly rescues microcephaly of all 3 EJC mutants. This implicates p53 activation as a major node of neurodevelopmental pathogenesis following EJC impairment. Altogether our study reveals new mechanisms to help explain how EJC mutations influence neurogenesis and underlie neurodevelopmental disease.

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10.1371/journal.pgen.1006282

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Mao, Hanqian, John J McMahon, Yi-Hsuan Tsai, Zefeng Wang and Debra L Silver (2016). Haploinsufficiency for Core Exon Junction Complex Components Disrupts Embryonic Neurogenesis and Causes p53-Mediated Microcephaly. PLoS Genet, 12(9). p. e1006282. 10.1371/journal.pgen.1006282 Retrieved from https://hdl.handle.net/10161/12975.

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Silver

Debra Lynn Silver

Professor of Molecular Genetics and Microbiology

How is the brain assembled and sculpted during embryonic development?  Addressing this question has enormous implications for understanding neurodevelopmental disorders affecting brain size and function. In evolutionary terms, our newest brain structure is the cerebral cortex, which drives higher cognitive capacities. The overall mission of my research lab is to elucidate genetic and cellular mechanisms controlling cortical development and contributing to neurodevelopmental pathologies and brain evolution. We study neural progenitors, essential cells which generate neurons and are the root of brain development. We are guided by the premise that the same mechanisms at play during normal development were co-opted during evolution and when dysregulated, can cause neurodevelopmental disease.

My research program employs a multifaceted strategy to bridge developmental neurobiology, RNA biology, and evolution. 1) We investigate how cell fates are specified, by studying how progenitor divisions influence development and disease.  2) We study diverse layers of post-transcriptional regulation in neural progenitors. We investigate RNA binding proteins implicated in development and neurological disease. Using live imaging, we also investigate how sub-cellular control of mRNA localization and translation influences neural progenitors. 3) A parallel research focus is to understand how human-specific genetic changes influence species-specific brain development. Our goal is to integrate our efforts across these three major lines of research to understand the intricacies controlling brain development.


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