@article {391, title = {Heterozygous variants in ACTL6A, encoding a component of the BAF complex, are associated with intellectual disability.}, journal = {Hum Mutat}, volume = {38}, year = {2017}, month = {2017 10}, pages = {1365-1371}, abstract = {

Pathogenic variants in genes encoding components of the BRG1-associated factor (BAF) chromatin remodeling complex have been associated with intellectual disability syndromes. We identified heterozygous, novel variants in ACTL6A, a gene encoding a component of the BAF complex, in three subjects with varying degrees of intellectual disability. Two subjects have missense variants affecting highly conserved amino acid residues within the actin-like domain. Missense mutations in the homologous region in yeast actin were previously reported to be dominant lethal and were associated with impaired binding of the human ACTL6A to β-actin and BRG1. A third subject has a splicing variant that creates an in-frame deletion. Our findings suggest that the variants identified in our subjects may have a deleterious effect on the function of the protein by disturbing the integrity of the BAF complex. Thus, ACTL6A gene mutation analysis should be considered in patients with intellectual disability, learning disabilities, or developmental language disorder.

}, keywords = {Actins, Adolescent, Child, Chromatin Assembly and Disassembly, Chromosomal Proteins, Non-Histone, DNA Helicases, DNA-Binding Proteins, Exome, Face, Female, Hand Deformities, Congenital, Heterozygote, Humans, Intellectual Disability, Male, Micrognathism, Multiprotein Complexes, Mutation, Missense, Nuclear Proteins, Protein Binding, Transcription Factors}, issn = {1098-1004}, doi = {10.1002/humu.23282}, author = {Marom, Ronit and Jain, Mahim and Burrage, Lindsay C and Song, I-Wen and Graham, Brett H and Brown, Chester W and Stevens, Servi J C and Stegmann, Alexander P A and Gunter, Andrew T and Kaplan, Julie D and Gavrilova, Ralitza H and Shinawi, Marwan and Rosenfeld, Jill A and Bae, Yangjin and Tran, Alyssa A and Chen, Yuqing and Lu, James T and Gibbs, Richard A and Eng, Christine and Yang, Yaping and Rousseau, Justine and de Vries, Bert B A and Campeau, Philippe M and Lee, Brendan} } @article {337, title = {Loss of Nardilysin, a Mitochondrial Co-chaperone for α-Ketoglutarate Dehydrogenase, Promotes mTORC1 Activation and Neurodegeneration.}, journal = {Neuron}, volume = {93}, year = {2017}, month = {2017 Jan 04}, pages = {115-131}, abstract = {

We previously identified mutations in Nardilysin (dNrd1) in a forward genetic screen designed to isolate genes whose loss causes neurodegeneration in Drosophila photoreceptor neurons. Here~we show that NRD1 is localized to mitochondria, where it recruits mitochondrial chaperones and assists in the folding of α-ketoglutarate dehydrogenase (OGDH), a rate-limiting enzyme in~the Krebs cycle. Loss of Nrd1 or Ogdh leads to an increase in α-ketoglutarate, a substrate for OGDH,~which in turn leads to mTORC1 activation and a subsequent reduction in autophagy. Inhibition of mTOR activity by rapamycin or partially restoring autophagy delays neurodegeneration in dNrd1 mutant flies. In summary, this study reveals a novel role for NRD1 as a mitochondrial co-chaperone for OGDH and provides a mechanistic link between mitochondrial metabolic dysfunction, mTORC1 signaling, and impaired autophagy in neurodegeneration.

}, keywords = {Animals, Autophagy, Drosophila, Drosophila melanogaster, Drosophila Proteins, Ketoglutarate Dehydrogenase Complex, Ketoglutaric Acids, Lysine, Mechanistic Target of Rapamycin Complex 1, Metalloendopeptidases, Mitochondria, Molecular Chaperones, Multiprotein Complexes, Neurodegenerative Diseases, TOR Serine-Threonine Kinases}, issn = {1097-4199}, doi = {10.1016/j.neuron.2016.11.038}, author = {Yoon, Wan Hee and Sandoval, Hector and Nagarkar-Jaiswal, Sonal and Jaiswal, Manish and Yamamoto, Shinya and Haelterman, Nele A and Putluri, Nagireddy and Putluri, Vasanta and Sreekumar, Arun and Tos, Tulay and Aksoy, Ayse and Donti, Taraka and Graham, Brett H and Ohno, Mikiko and Nishi, Eiichiro and Hunter, Jill and Muzny, Donna M and Carmichael, Jason and Shen, Joseph and Arboleda, Valerie A and Nelson, Stanley F and Wangler, Michael F and Karaca, Ender and Lupski, James R and Bellen, Hugo J} } @article {634, title = {Mutations in KEOPS-complex genes cause nephrotic syndrome with primary microcephaly.}, journal = {Nat Genet}, volume = {49}, year = {2017}, month = {2017 Oct}, pages = {1529-1538}, abstract = {

Galloway-Mowat syndrome (GAMOS) is an autosomal-recessive disease characterized by the combination of early-onset nephrotic syndrome (SRNS) and microcephaly with brain anomalies. Here we identified recessive mutations in OSGEP, TP53RK, TPRKB, and LAGE3, genes encoding the four subunits of the KEOPS complex, in 37 individuals from 32 families with GAMOS. CRISPR-Cas9 knockout in zebrafish and mice recapitulated the human phenotype of primary microcephaly and resulted in early lethality. Knockdown of OSGEP, TP53RK, or TPRKB inhibited cell proliferation, which human mutations did not rescue. Furthermore, knockdown of these genes impaired protein translation, caused endoplasmic reticulum stress, activated DNA-damage-response signaling, and ultimately induced apoptosis. Knockdown of OSGEP or TP53RK induced defects in the actin cytoskeleton and decreased the migration rate of human podocytes, an established intermediate phenotype of SRNS. We thus identified four new monogenic causes of GAMOS, describe a link between KEOPS function and human disease, and delineate potential pathogenic mechanisms.

}, keywords = {Animals, Apoptosis, Carrier Proteins, Cell Movement, CRISPR-Cas Systems, Cytoskeleton, DNA Repair, Endoplasmic Reticulum Stress, Gene Knockout Techniques, Hernia, Hiatal, Humans, Intracellular Signaling Peptides and Proteins, Metalloendopeptidases, Mice, Microcephaly, Models, Molecular, Multiprotein Complexes, Mutation, Nephrosis, Nephrotic Syndrome, Podocytes, Protein Conformation, Protein-Serine-Threonine Kinases, RNA Processing, Post-Transcriptional, RNA, Transfer, Telomere Homeostasis, Zebrafish, Zebrafish Proteins}, issn = {1546-1718}, doi = {10.1038/ng.3933}, author = {Braun, Daniela A and Rao, Jia and Mollet, Geraldine and Schapiro, David and Daugeron, Marie-Claire and Tan, Weizhen and Gribouval, Olivier and Boyer, Olivia and Revy, Patrick and Jobst-Schwan, Tilman and Schmidt, Johanna Magdalena and Lawson, Jennifer A and Schanze, Denny and Ashraf, Shazia and Ullmann, Jeremy F P and Hoogstraten, Charlotte A and Boddaert, Nathalie and Collinet, Bruno and Martin, Ga{\"e}lle and Liger, Dominique and Lovric, Svjetlana and Furlano, Monica and Guerrera, I Chiara and Sanchez-Ferras, Oraly and Hu, Jennifer F and Boschat, Anne-Claire and Sanquer, Sylvia and Menten, Bj{\"o}rn and Vergult, Sarah and De Rocker, Nina and Airik, Merlin and Hermle, Tobias and Shril, Shirlee and Widmeier, Eugen and Gee, Heon Yung and Choi, Won-Il and Sadowski, Carolin E and Pabst, Werner L and Warejko, Jillian K and Daga, Ankana and Basta, Tamara and Matejas, Verena and Scharmann, Karin and Kienast, Sandra D and Behnam, Babak and Beeson, Brendan and Begtrup, Amber and Bruce, Malcolm and Ch{\textquoteright}ng, Gaik-Siew and Lin, Shuan-Pei and Chang, Jui-Hsing and Chen, Chao-Huei and Cho, Megan T and Gaffney, Patrick M and Gipson, Patrick E and Hsu, Chyong-Hsin and Kari, Jameela A and Ke, Yu-Yuan and Kiraly-Borri, Cathy and Lai, Wai-Ming and Lemyre, Emmanuelle and Littlejohn, Rebecca Okashah and Masri, Amira and Moghtaderi, Mastaneh and Nakamura, Kazuyuki and Ozaltin, Fatih and Praet, Marleen and Prasad, Chitra and Prytula, Agnieszka and Roeder, Elizabeth R and Rump, Patrick and Schnur, Rhonda E and Shiihara, Takashi and Sinha, Manish D and Soliman, Neveen A and Soulami, Kenza and Sweetser, David A and Tsai, Wen-Hui and Tsai, Jeng-Daw and Topaloglu, Rezan and Vester, Udo and Viskochil, David H and Vatanavicharn, Nithiwat and Waxler, Jessica L and Wierenga, Klaas J and Wolf, Matthias T F and Wong, Sik-Nin and Leidel, Sebastian A and Truglio, Gessica and Dedon, Peter C and Poduri, Annapurna and Mane, Shrikant and Lifton, Richard P and Bouchard, Maxime and Kannu, Peter and Chitayat, David and Magen, Daniella and Callewaert, Bert and van Tilbeurgh, Herman and Zenker, Martin and Antignac, Corinne and Hildebrandt, Friedhelm} } @article {58, title = {Association of MTOR Mutations With Developmental Brain Disorders, Including Megalencephaly, Focal Cortical Dysplasia, and Pigmentary Mosaicism.}, journal = {JAMA Neurol}, volume = {73}, year = {2016}, month = {2016 07 01}, pages = {836-845}, abstract = {

IMPORTANCE: Focal cortical dysplasia (FCD), hemimegalencephaly, and megalencephaly constitute a spectrum of malformations of cortical development with shared neuropathologic features. These disorders are associated with significant childhood morbidity and mortality.

OBJECTIVE: To identify the underlying molecular cause of FCD, hemimegalencephaly, and diffuse megalencephaly.

DESIGN, SETTING, AND PARTICIPANTS: Patients with FCD, hemimegalencephaly, or megalencephaly (mean age, 11.7 years; range, 2-32 years) were recruited from Pediatric Hospital A. Meyer, the University of Hong Kong, and Seattle Children{\textquoteright}s Research Institute from June 2012 to June 2014. Whole-exome sequencing (WES) was performed on 8 children with FCD or hemimegalencephaly using standard-depth (50-60X) sequencing in peripheral samples (blood, saliva, or skin) from the affected child and their parents and deep (150-180X) sequencing in affected brain tissue. Targeted sequencing and WES were used to screen 93 children with molecularly unexplained diffuse or focal brain overgrowth. Histopathologic and functional assays of phosphatidylinositol 3-kinase-AKT (serine/threonine kinase)-mammalian target of rapamycin (mTOR) pathway activity in resected brain tissue and cultured neurons were performed to validate mutations.

MAIN OUTCOMES AND MEASURES: Whole-exome sequencing and targeted sequencing identified variants associated with this spectrum of developmental brain disorders.

RESULTS: Low-level mosaic mutations of MTOR were identified in brain tissue in 4 children with FCD type 2a with alternative allele fractions ranging from 0.012 to 0.086. Intermediate-level mosaic mutation of MTOR (p.Thr1977Ile) was also identified in 3 unrelated children with diffuse megalencephaly and pigmentary mosaicism in skin. Finally, a constitutional de novo mutation of MTOR (p.Glu1799Lys) was identified in 3 unrelated children with diffuse megalencephaly and intellectual disability. Molecular and functional analysis in 2 children with FCD2a from whom multiple affected brain tissue samples were available revealed a mutation gradient with an epicenter in the most epileptogenic area. When expressed in cultured neurons, all MTOR mutations identified here drive constitutive activation of mTOR complex 1 and enlarged neuronal size.

CONCLUSIONS AND RELEVANCE: In this study, mutations of MTOR were associated with a spectrum of brain overgrowth phenotypes extending from FCD type 2a to diffuse megalencephaly, distinguished by different mutations and levels of mosaicism. These mutations may be sufficient to cause cellular hypertrophy in cultured neurons and may provide a demonstration of the pattern of mosaicism in brain and substantiate the link between mosaic mutations of MTOR and pigmentary mosaicism in skin.

}, keywords = {Adolescent, Adult, Amino Acids, Animals, Cells, Cultured, Cerebral Cortex, Child, Child, Preschool, Developmental Disabilities, Embryo, Mammalian, Female, Gene Expression Regulation, Genetic Association Studies, Humans, Intercellular Signaling Peptides and Proteins, Male, Malformations of Cortical Development, Mechanistic Target of Rapamycin Complex 1, Megalencephaly, Mosaicism, Multiprotein Complexes, Mutation, Nerve Tissue Proteins, Neurons, Rats, Retrospective Studies, TOR Serine-Threonine Kinases, Young Adult}, issn = {2168-6157}, doi = {10.1001/jamaneurol.2016.0363}, author = {Mirzaa, Ghayda M and Campbell, Catarina D and Solovieff, Nadia and Goold, Carleton and Jansen, Laura A and Menon, Suchithra and Timms, Andrew E and Conti, Valerio and Biag, Jonathan D and Adams, Carissa and Boyle, Evan August and Collins, Sarah and Ishak, Gisele and Poliachik, Sandra and Girisha, Katta M and Yeung, Kit San and Chung, Brian Hon Yin and Rahikkala, Elisa and Gunter, Sonya A and McDaniel, Sharon S and Macmurdo, Colleen Forsyth and Bernstein, Jonathan A and Martin, Beth and Leary, Rebecca and Mahan, Scott and Liu, Shanming and Weaver, Molly and Doerschner, Michael and Jhangiani, Shalini and Muzny, Donna M and Boerwinkle, Eric and Gibbs, Richard A and Lupski, James R and Shendure, Jay and Saneto, Russell P and Novotny, Edward J and Wilson, Christopher J and Sellers, William R and Morrissey, Michael and Hevner, Robert F and Ojemann, Jeffrey G and Guerrini, Renzo and Murphy, Leon O and Winckler, Wendy and Dobyns, William B} } @article {35, title = {IFT52 mutations destabilize anterograde complex assembly, disrupt ciliogenesis and result in short rib polydactyly syndrome.}, journal = {Hum Mol Genet}, volume = {25}, year = {2016}, month = {2016 Sep 15}, pages = {4012-4020}, abstract = {

The short-rib polydactyly syndromes (SRPS) encompass a radiographically and genetically heterogeneous group of skeletal ciliopathies that are characterized by a long narrow chest, short extremities, and variable occurrence of polydactyly. Radiographic abnormalities include undermineralization of the calvarium, shortened and bowed appendicular bones, trident shaped acetabula and polydactyly. In a case of SRPS we identified compound heterozygosity for mutations in IFT52, which encodes a component of the anterograde intraflagellar transport complex. The IFT52 mutant cells synthesized a significantly reduced amount of IFT52 protein, leading to reduced synthesis of IFT74, IFT81, IFT88 and ARL13B, other key anterograde complex members. Ciliogenesis was also disrupted in the mutant cells, with a 60\% reduction in the presence of cilia on mutant cells and loss of cilia length regulation for the cells with cilia. These data demonstrate that IFT52 is essential for anterograde complex integrity and for the biosynthesis and maintenance of cilia. The data identify a new locus for SRPS and show that IFT52 mutations result in a ciliopathy with primary effects on the skeleton.

}, keywords = {Carrier Proteins, Cilia, Ciliopathies, Cytoskeletal Proteins, Flagella, Humans, Intracellular Signaling Peptides and Proteins, Multiprotein Complexes, Muscle Proteins, Mutation, Short Rib-Polydactyly Syndrome, Skeleton, Tumor Suppressor Proteins}, issn = {1460-2083}, doi = {10.1093/hmg/ddw241}, author = {Zhang, Wenjuan and Taylor, S Paige and Nevarez, Lisette and Lachman, Ralph S and Nickerson, Deborah A and Bamshad, Michael and Krakow, Deborah and Cohn, Daniel H} }