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Browsing by Author "Niu, Zhiyv"
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Item Evidence for replicative mechanism in a CHD7 rearrangement in a patient with CHARGE syndrome(Wiley, 2013-12) Vatta, Matteo; Niu, Zhiyv; Lupski, James R.; Putnam, Philip; Spoonamore, Katherine G.; Fang, Ping; Eng, Christine M.; Willis, Alecia S.; Medical & Molecular Genetics, School of MedicineHaploinsufficiency of CHD7 (OMIM# 608892) is known to cause CHARGE syndrome (OMIM# 214800). Molecular testing supports a definitive diagnosis in approximately 65-70% of cases. Most CHD7 mutations arise de novo, and no mutations affecting exon-7 have been reported to date. We report on an 8-year-old girl diagnosed with CHARGE syndrome that was referred to our laboratory for comprehensive CHD7 gene screening. Genomic DNA from the subject with a suspected diagnosis of CHARGE was isolated from peripheral blood lymphocytes and comprehensive Sanger sequencing, along with deletion/duplication analysis of the CHD7 gene using multiplex ligation-dependent probe amplification (MLPA), was performed. MLPA analysis identified a reduced single probe signal for exon-7 of the CHD7 gene consistent with potential heterozygous deletion. Long-range PCR breakpoint analysis identified a complex genomic rearrangement (CGR) leading to the deletion of exon-7 and breakpoints consistent with a replicative mechanism such as fork stalling and template switching (FoSTeS) or microhomology-mediated break-induced replication (MMBIR). Taken together this represents the first evidence for a CHD7 intragenic CGR in a patient with CHARGE syndrome leading to what appears to be also the first report of a mutation specifically disrupting exon-7. Although likely rare, CGR may represent an overlooked mechanism in subjects with CHARGE syndrome that can be missed by current sequencing and dosage assays.Item Germline variants in tumor suppressor FBXW7 lead to impaired ubiquitination and a neurodevelopmental syndrome(Elsevier, 2022) Stephenson, Sarah E.M.; Costain, Gregory; Blok, Laura E.R.; Silk, Michael A.; Nguyen, Thanh Binh; Dong, Xiaomin; Alhuzaimi, Dana E.; Dowling, James J.; Walker, Susan; Amburgey, Kimberly; Hayeems, Robin Z.; Rodan, Lance H.; Schwartz, Marc A.; Picker, Jonathan; Lynch, Sally A.; Gupta, Aditi; Rasmussen, Kristen J.; Schimmenti, Lisa A.; Klee, Eric W.; Niu, Zhiyv; Agre, Katherine E.; Chilton, Ilana; Chung, Wendy K.; Revah-Politi, Anya; Au, P.Y. Billie; Griffith, Christopher; Racobaldo, Melissa; Raas-Rothschild, Annick; Zeev, Bruria Ben; Barel, Ortal; Moutton, Sebastien; Morice-Picard, Fanny; Carmignac, Virginie; Cornaton, Jenny; Marle, Nathalie; Devinsky, Orrin; Stimach, Chandler; Burns Wechsler, Stephanie; Hainline, Bryan E.; Sapp, Katie; Willems, Marjolaine; Bruel, Ange-Line; Dias, Kerith-Rae; Evans, Carey-Anne; Roscioli, Tony; Sachdev, Rani; Temple, Suzanna E.L.; Zhu, Ying; Baker, Joshua J.; Scheffer, Ingrid E.; Gardiner, Fiona J.; Schneider, Amy L.; Muir, Alison M.; Mefford, Heather C.; Crunk, Amy; Heise, Elizabeth M.; Millan, Francisca; Monaghan, Kristin G.; Person, Richard; Rhodes, Lindsay; Richards, Sarah; Wentzensen, Ingrid M.; Cogné, Benjamin; Isidor, Bertrand; Nizon, Mathilde; Vincent, Marie; Besnard, Thomas; Piton, Amelie; Marcelis, Carlo; Kato, Kohji; Koyama, Norihisa; Ogi, Tomoo; Suk-Ying Goh, Elaine; Richmond, Christopher; Amor, David J.; Boyce, Jessica O.; Morgan, Angela T.; Hildebrand, Michael S.; Kaspi, Antony; Bahlo, Melanie; Friðriksdóttir, Rún; Katrínardóttir, Hildigunnur; Sulem, Patrick; Stefánsson, Kári; Björnsson, Hans Tómas; Mandelstam, Simone; Morleo, Manuela; Mariani, Milena; TUDP Study Group; Scala, Marcello; Accogli, Andrea; Torella, Annalaura; Capra, Valeria; Wallis, Mathew; Jansen, Sandra; Weisfisz, Quinten; de Haan, Hugoline; Sadedin, Simon; Broad Center for Mendelian Genomics; Lim, Sze Chern; White, Susan M.; Ascher, David B.; Schenck, Annette; Lockhart, Paul J.; Christodoulou, John; Tan, Tiong Yang; Medical and Molecular Genetics, School of MedicineNeurodevelopmental disorders are highly heterogenous conditions resulting from abnormalities of brain architecture and/or function. FBXW7 (F-box and WD-repeat-domain-containing 7), a recognized developmental regulator and tumor suppressor, has been shown to regulate cell-cycle progression and cell growth and survival by targeting substrates including CYCLIN E1/2 and NOTCH for degradation via the ubiquitin proteasome system. We used a genotype-first approach and global data-sharing platforms to identify 35 individuals harboring de novo and inherited FBXW7 germline monoallelic chromosomal deletions and nonsense, frameshift, splice-site, and missense variants associated with a neurodevelopmental syndrome. The FBXW7 neurodevelopmental syndrome is distinguished by global developmental delay, borderline to severe intellectual disability, hypotonia, and gastrointestinal issues. Brain imaging detailed variable underlying structural abnormalities affecting the cerebellum, corpus collosum, and white matter. A crystal-structure model of FBXW7 predicted that missense variants were clustered at the substrate-binding surface of the WD40 domain and that these might reduce FBXW7 substrate binding affinity. Expression of recombinant FBXW7 missense variants in cultured cells demonstrated impaired CYCLIN E1 and CYCLIN E2 turnover. Pan-neuronal knockdown of the Drosophila ortholog, archipelago, impaired learning and neuronal function. Collectively, the data presented herein provide compelling evidence of an F-Box protein-related, phenotypically variable neurodevelopmental disorder associated with monoallelic variants in FBXW7.Item Myogenesis defects in a patient-derived iPSC model of hereditary GNE myopathy(Springer Nature, 2022-09-09) Schmitt, Rebecca E.; Smith, Douglas Y., IV.; Cho, Dong Seong; Kirkeby, Lindsey A.; Resch, Zachary T.; Liewluck, Teerin; Niu, Zhiyv; Milone, Margherita; Doles, Jason D.; Anatomy, Cell Biology and Physiology, School of MedicineHereditary muscle diseases are disabling disorders lacking effective treatments. UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) myopathy (GNEM) is an autosomal recessive distal myopathy with rimmed vacuoles typically manifesting in late adolescence/early adulthood. GNE encodes the rate-limiting enzyme in sialic acid biosynthesis, which is necessary for the proper function of numerous biological processes. Outside of the causative gene, very little is known about the mechanisms contributing to the development of GNE myopathy. In the present study, we aimed to address this knowledge gap by querying the underlying mechanisms of GNE myopathy using a patient-derived induced pluripotent stem-cell (iPSC) model. Control and patient-specific iPSCs were differentiated down a skeletal muscle lineage, whereby patient-derived GNEM iPSC clones were able to recapitulate key characteristics of the human pathology and further demonstrated defects in myogenic progression. Single-cell RNA sequencing time course studies revealed clear differences between control and GNEM iPSC-derived muscle precursor cells (iMPCs), while pathway studies implicated altered stress and autophagy signaling in GNEM iMPCs. Treatment of GNEM patient-derived iMPCs with an autophagy activator improved myogenic differentiation. In summary, we report an in vitro, iPSC-based model of GNE myopathy and implicate defective myogenesis as a contributing mechanism to the etiology of GNE myopathy.