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Williams SE, Garcia I, Crowther AJ, Li S, Stewart A, Liu H, Lough KJ, O'Neill S, Veleta K, Oyarzabal EA, Merrill JR, Shih YYI, Gershon TR. Aspm sustains postnatal cerebellar neurogenesis and medulloblastoma growth in mice. Development 2015; 142:3921-32. [PMID: 26450969 DOI: 10.1242/dev.124271] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 09/28/2015] [Indexed: 01/06/2023]
Abstract
Alterations in genes that regulate brain size may contribute to both microcephaly and brain tumor formation. Here, we report that Aspm, a gene that is mutated in familial microcephaly, regulates postnatal neurogenesis in the cerebellum and supports the growth of medulloblastoma, the most common malignant pediatric brain tumor. Cerebellar granule neuron progenitors (CGNPs) express Aspm when maintained in a proliferative state by sonic hedgehog (Shh) signaling, and Aspm is expressed in Shh-driven medulloblastoma in mice. Genetic deletion of Aspm reduces cerebellar growth, while paradoxically increasing the mitotic rate of CGNPs. Aspm-deficient CGNPs show impaired mitotic progression, altered patterns of division orientation and differentiation, and increased DNA damage, which causes progenitor attrition through apoptosis. Deletion of Aspm in mice with Smo-induced medulloblastoma reduces tumor growth and increases DNA damage. Co-deletion of Aspm and either of the apoptosis regulators Bax or Trp53 (also known as p53) rescues the survival of neural progenitors and reduces the growth restriction imposed by Aspm deletion. Our data show that Aspm functions to regulate mitosis and to mitigate DNA damage during CGNP cell division, causes microcephaly through progenitor apoptosis when mutated, and sustains tumor growth in medulloblastoma.
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Affiliation(s)
- Scott E Williams
- Department of Pathology & Laboratory Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Idoia Garcia
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Andrew J Crowther
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Shiyi Li
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Alyssa Stewart
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Hedi Liu
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Kendall J Lough
- Department of Pathology & Laboratory Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Sean O'Neill
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Katherine Veleta
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Esteban A Oyarzabal
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Joseph R Merrill
- Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yen-Yu Ian Shih
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC 27599, USA Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Timothy R Gershon
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA UNC Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
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152
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Narayanan M, Ramsey K, Grebe T, Schrauwen I, Szelinger S, Huentelman M, Craig D, Narayanan V. Case Report: Compound heterozygous nonsense mutations in TRMT10A are associated with microcephaly, delayed development, and periventricular white matter hyperintensities. F1000Res 2015; 4:912. [PMID: 26535115 PMCID: PMC4617320 DOI: 10.12688/f1000research.7106.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/24/2015] [Indexed: 12/29/2022] Open
Abstract
Microcephaly is a fairly common feature observed in children with delayed development, defined as head circumference less than 2 standard deviations below the mean for age and gender. It may be the result of an acquired insult to the brain, such prenatal or perinatal brain injury (congenital infection or hypoxic ischemic encephalopathy), or be a part of a genetic syndrome. There are over 1000 conditions listed in OMIM (Online Mendelian Inheritance in Man) where microcephaly is a key finding; many of these are associated with specific somatic features and non-CNS anomalies. The term primary microcephaly is used when microcephaly and delayed development are the primary features, and they are not part of another recognized syndrome. In this case report, we present the clinical features of siblings (brother and sister) with primary microcephaly and delayed development, and subtle dysmorphic features. Both children had brain MRI studies that showed periventricular and subcortical T2/FLAIR hyperintensities, without signs of white matter volume loss, and no parenchymal calcifications by CT scan. The family was enrolled in a research study for whole exome sequencing of probands and parents. Analysis of variants determined that the children were compound heterozygotes for nonsense mutations, c.277C>T (p.Arg93*) and c.397C>T (p.Arg133*), in the
TRMT10A gene. Mutations in this gene have only recently been reported in children with microcephaly and early onset diabetes mellitus. Our report adds to current knowledge of
TRMT10A related neurodevelopmental disorders and demonstrates imaging findings suggestive of delayed or abnormal myelination of the white matter in this disorder. Accurate diagnosis through genomic testing, as in the children described here, allows for early detection and management of medical complications, such as diabetes mellitus.
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Affiliation(s)
- Mohan Narayanan
- Arizona Pediatric Neurology & Neurogenetics Associates, Phoenix, AZ, USA ; Barrow Neurological Institute, Phoenix, AZ, USA
| | - Keri Ramsey
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, USA ; Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ, USA
| | - Theresa Grebe
- Department of Genetics, Phoenix Children's Hospital, Phoenix, AZ, USA
| | - Isabelle Schrauwen
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, USA ; Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ, USA
| | - Szabolcs Szelinger
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, USA ; Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ, USA
| | - Matthew Huentelman
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, USA ; Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ, USA
| | - David Craig
- Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, USA ; Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ, USA
| | - Vinodh Narayanan
- Arizona Pediatric Neurology & Neurogenetics Associates, Phoenix, AZ, USA ; Barrow Neurological Institute, Phoenix, AZ, USA ; Center for Rare Childhood Disorders, Translational Genomics Research Institute, Phoenix, AZ, USA ; Neurogenomics Division, Translational Genomics Research Institute, Phoenix, AZ, USA
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153
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Mumtaz S, Yıldız E, Jabeen S, Khan A, Tolun A, Malik S. RBBP8 syndrome with microcephaly, intellectual disability, short stature and brachydactyly. Am J Med Genet A 2015; 167A:3148-52. [PMID: 26333564 DOI: 10.1002/ajmg.a.37299] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Accepted: 07/31/2015] [Indexed: 11/08/2022]
Abstract
Primary microcephaly is clinically variable and genetically heterogeneous. Four phenotypically distinct types of autosomal recessive microcephaly syndromes are due to different RBBP8 mutations. We report on a consanguineous Pakistani family with homozygous RBBP8 mutation c.1808_1809delTA (p.Ile603Lysfs*7) manifesting microcephaly and a distinct combination of skeletal, limb and ectodermal defects, mild intellectual disability, minor facial anomalies, anonychia, disproportionate short stature and brachydactyly, and additionally talipes in one patient.
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Affiliation(s)
- Sara Mumtaz
- Department of Animal Sciences, Human Genetics Program, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
| | - Esra Yıldız
- Department of Molecular Biology and Genetics, Boğaziçi University, Istanbul, Turkey
| | - Saliha Jabeen
- Department of Animal Sciences, Human Genetics Program, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
| | - Amjad Khan
- Department of Animal Sciences, Human Genetics Program, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
| | - Aslıhan Tolun
- Department of Molecular Biology and Genetics, Boğaziçi University, Istanbul, Turkey
| | - Sajid Malik
- Department of Animal Sciences, Human Genetics Program, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
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154
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Kodani A, Yu TW, Johnson JR, Jayaraman D, Johnson TL, Al-Gazali L, Sztriha L, Partlow JN, Kim H, Krup AL, Dammermann A, Krogan NJ, Walsh CA, Reiter JF. Centriolar satellites assemble centrosomal microcephaly proteins to recruit CDK2 and promote centriole duplication. eLife 2015; 4:e07519. [PMID: 26297806 PMCID: PMC4574112 DOI: 10.7554/elife.07519] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 08/21/2015] [Indexed: 12/23/2022] Open
Abstract
Primary microcephaly (MCPH) associated proteins CDK5RAP2, CEP152, WDR62 and CEP63 colocalize at the centrosome. We found that they interact to promote centriole duplication and form a hierarchy in which each is required to localize another to the centrosome, with CDK5RAP2 at the apex, and CEP152, WDR62 and CEP63 at sequentially lower positions. MCPH proteins interact with distinct centriolar satellite proteins; CDK5RAP2 interacts with SPAG5 and CEP72, CEP152 with CEP131, WDR62 with MOONRAKER, and CEP63 with CEP90 and CCDC14. These satellite proteins localize their cognate MCPH interactors to centrosomes and also promote centriole duplication. Consistent with a role for satellites in microcephaly, homozygous mutations in one satellite gene, CEP90, may cause MCPH. The satellite proteins, with the exception of CCDC14, and MCPH proteins promote centriole duplication by recruiting CDK2 to the centrosome. Thus, centriolar satellites build a MCPH complex critical for human neurodevelopment that promotes CDK2 centrosomal localization and centriole duplication.
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Affiliation(s)
- Andrew Kodani
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
| | - Timothy W Yu
- Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States
| | - Jeffrey R Johnson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Divya Jayaraman
- Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States
| | - Tasha L Johnson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine and Health Sciences, United Arab Emirates University, Al-Ain, United Arab Emirates
| | - Lāszló Sztriha
- Department of Paediatrics, College of Medicine and Health Sciences, United Arab Emirates University, Al-Ain, United Arab Emirates
| | - Jennifer N Partlow
- Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States
| | - Hanjun Kim
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
| | - Alexis L Krup
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
| | | | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Christopher A Walsh
- Howard Hughes Medical Institute, Boston Children's Hospital, Boston, United States
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
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155
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Rosales-Reynoso MA, Juárez-Vázquez CI, Barros-Núñez P. Evolution and genomics of the human brain. Neurologia 2015; 33:254-265. [PMID: 26304653 DOI: 10.1016/j.nrl.2015.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 06/01/2015] [Indexed: 01/20/2023] Open
Abstract
Most living beings are able to perform actions that can be considered intelligent or, at the very least, the result of an appropriate reaction to changing circumstances in their environment. However, the intelligence or intellectual processes of humans are vastly superior to those achieved by all other species. The adult human brain is a highly complex organ weighing approximately 1500g, which accounts for only 2% of the total body weight but consumes an amount of energy equal to that required by all skeletal muscle at rest. Although the human brain displays a typical primate structure, it can be identified by its specific distinguishing features. The process of evolution and humanisation of the Homo sapiens brain resulted in a unique and distinct organ with the largest relative volume of any animal species. It also permitted structural reorganization of tissues and circuits in specific segments and regions. These steps explain the remarkable cognitive abilities of modern humans compared not only with other species in our genus, but also with older members of our own species. Brain evolution required the coexistence of two adaptation mechanisms. The first involves genetic changes that occur at the species level, and the second occurs at the individual level and involves changes in chromatin organisation or epigenetic changes. The genetic mechanisms include: a) genetic changes in coding regions that lead to changes in the sequence and activity of existing proteins; b) duplication and deletion of previously existing genes; c) changes in gene expression through changes in the regulatory sequences of different genes; and d) synthesis of non-coding RNAs. Lastly, this review describes some of the main documented chromosomal differences between humans and great apes. These differences have also contributed to the evolution and humanisation process of the H. sapiens brain.
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Affiliation(s)
- M A Rosales-Reynoso
- División de Medicina Molecular, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México
| | - C I Juárez-Vázquez
- División de Medicina Molecular, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México
| | - P Barros-Núñez
- División de Genética, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México.
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156
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Tubulinopathies and Their Brain Malformation Syndromes: Every TUB on Its Own Bottom. Epilepsy Curr 2015; 15:65-7. [PMID: 26251641 DOI: 10.5698/1535-7597-15.2.65] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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157
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Shi L, Lin Q, Su B. Estrogen regulation of microcephaly genes and evolution of brain sexual dimorphism in primates. BMC Evol Biol 2015; 15:127. [PMID: 26123139 PMCID: PMC4487212 DOI: 10.1186/s12862-015-0398-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/29/2015] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Sexual dimorphism in brain size is common among primates, including humans, apes and some Old World monkeys. In these species, the brain size of males is generally larger than that of females. Curiously, this dimorphism has persisted over the course of primate evolution and human origin, but there is no explanation for the underlying genetic controls that have maintained this disparity in brain size. RESULTS In the present study, we tested the effect of the female hormone (estradiol) on seven genes known to be related to brain size in both humans and nonhuman primates, and we identified half estrogen responsive elements (half EREs) in the promoter regions of four genes (MCPH1, ASPM, CDK5RAP2 and WDR62). Likewise, at sequence level, it appears that these half EREs are generally conserved across primates. Later testing via a reporter gene assay and cell-based endogenous expression measurement revealed that estradiol could significantly suppress the expression of the four affected genes involved in brain size. More intriguingly, when the half EREs were deleted from the promoters, the suppression effect disappeared, suggesting that the half EREs mediate the regulation of estradiol on the brain size genes. We next replicated these experiments using promoter sequences from chimpanzees and rhesus macaques, and observed a similar suppressive effect of estradiol on gene expression, suggesting that this mechanism is conserved among primate species that exhibit brain size dimorphism. CONCLUSIONS Brain size dimorphism among certain primates, including humans, is likely regulated by estrogen through its sex-dependent suppression of brain size genes during development.
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Affiliation(s)
- Lei Shi
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiao-Chang Road, Kunming, 650223, Yunnan, PR China. .,Yunnan Key Laboratory of Primate Biomedical Research, Kunming, 650000, China.
| | - Qiang Lin
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiao-Chang Road, Kunming, 650223, Yunnan, PR China. .,Yunnan Key Laboratory of Primate Biomedical Research, Kunming, 650000, China. .,Kunming College of Life Science, University of Chinese Academy of Sciences, Beijing, 100101, China.
| | - Bing Su
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 East Jiao-Chang Road, Kunming, 650223, Yunnan, PR China. .,Yunnan Key Laboratory of Primate Biomedical Research, Kunming, 650000, China.
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158
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Wang J, Tao Y, Song F, Sun Y, Ott J, Saffen D. Common Regulatory Variants ofCYFIP1Contribute to Susceptibility for Autism Spectrum Disorder (ASD) and Classical Autism. Ann Hum Genet 2015; 79:329-340. [DOI: 10.1111/ahg.12121] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 04/08/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Jian Wang
- Institutes of Brain Science; Fudan University; Shanghai China
- School of Life Sciences; Fudan University; Shanghai China
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources; Shanghai Ocean University, Shanghai, Ministry of Education; China
| | - Yu Tao
- Department of Cellular and Genetic Medicine; Fudan University; Shanghai China
| | - Fan Song
- Department of Cellular and Genetic Medicine; Fudan University; Shanghai China
| | - Yue Sun
- Institutes of Brain Science; Fudan University; Shanghai China
- School of Life Sciences; Fudan University; Shanghai China
| | - Jurg Ott
- Institute of Psychology; Chinese Academy of Science; Beijing China
| | - David Saffen
- Institutes of Brain Science; Fudan University; Shanghai China
- School of Life Sciences; Fudan University; Shanghai China
- Department of Cellular and Genetic Medicine; Fudan University; Shanghai China
- State Key Laboratory of Medical Neurobiology; Fudan University; Shanghai China
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159
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Morris-Rosendahl DJ, Kaindl AM. What next-generation sequencing (NGS) technology has enabled us to learn about primary autosomal recessive microcephaly (MCPH). Mol Cell Probes 2015; 29:271-81. [PMID: 26050940 DOI: 10.1016/j.mcp.2015.05.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/28/2015] [Accepted: 05/29/2015] [Indexed: 11/27/2022]
Abstract
The impact that next-generation sequencing technology (NGS) is having on many aspects of molecular and cell biology, is becoming increasingly apparent. One of the most noticeable outcomes of the new technology in human genetics, has been the accelerated rate of identification of disease-causing genes. Especially for rare, heterogeneous disorders, such as autosomal recessive primary microcephaly (MCPH), the handful of genes previously known to harbour disease-causing mutations, has grown at an unprecedented rate within a few years. Knowledge of new genes mutated in MCPH over the last four years has contributed to our understanding of the disorder at both the clinical and cellular levels. The functions of proteins such as WDR62, CASC5, PHC1, CDK6, CENP-E, CENP-F, CEP63, ZNF335, PLK4 and TUBGPC, have been added to the complex network of critical cellular processes known to be involved in brain growth and size. In addition to the importance of mitotic spindle assembly and structure, centrosome and centriole function and DNA repair and damage response, new mechanisms involving kinetochore-associated proteins and chromatin remodelling complexes have been elucidated. Two of the major contributions to our clinical knowledge are the realisation that primary microcephaly caused by mutations in genes at the MCPH loci is seldom an isolated clinical feature and is often accompanied either by additional cortical malformations or primordial dwarfism. Gene-phenotype correlations are being revisited, with a new dimension of locus heterogeneity and phenotypic variability being revealed.
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Affiliation(s)
- Deborah J Morris-Rosendahl
- Clinical Genetics and Genomics, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom; National Heart and Lung Institute, Imperial College London, London, United Kingdom.
| | - Angela M Kaindl
- Department of Pediatric Neurology, Charité University Medicine, Berlin, Germany; Institute of Cell Biology and Neurobiology, Charité University Medicine, Berlin, Germany
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160
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The association of RAB18 gene polymorphism (rs3765133) with cerebellar volume in healthy adults. THE CEREBELLUM 2015; 13:616-22. [PMID: 24996981 DOI: 10.1007/s12311-014-0579-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Genetic factors are responsible for the development of the human brain. Certain genetic factors are known to increase the risk of common brain disorders and affect the brain structure. Therefore, even in healthy people, these factors have a role in the development of specific brain regions. Loss-of-function mutations in the RAB18 gene (RAB18) cause Warburg Micro syndrome, which is associated with reduced brain size and deformed brain structures. In this study, we hypothesized that the RAB18 variant might influence regional brain volumes in healthy people. The study participants comprised 246 normal volunteers between 21 and 59 years of age (mean age of 37.8 ± 12.0 years; 115 men, 131 women). Magnetic resonance imaging (MRI) and genotypes of RAB18 rs3765133 were examined for each participant. The differences in regional brain volumes between T homozygotes and A-allele carriers were tested using voxel-based morphometry. The results showed that RAB18 rs3765133 T homozygote group exhibited larger gray matter (GM) volume in the left middle temporal and inferior frontal gyrus of the cerebrum than the A-allele carriers. An opposite effect was observed in both the posterior lobes and right tonsil of the cerebellum, in which the GM volume of RAB18 rs3765133 T homozygotes was smaller than that of the A-allele carriers (all P FWE < 0.05). Our findings suggest that RAB18 rs3765133 polymorphism affects the deve-lopment of specific brain regions, particularly the cerebellum, in healthy people.
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161
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Li MH, Arndt K, Das S, Weiss EM, Wu Y, Gwal K, Shekdar KV, Zackai EH. Compound heterozygoteCDK5RAP2mutations in a Guatemalan/Honduran child with autosomal recessive primary microcephaly, failure to thrive and speech delay. Am J Med Genet A 2015; 167:1414-7. [DOI: 10.1002/ajmg.a.36975] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 12/11/2014] [Indexed: 01/23/2023]
Affiliation(s)
- Mindy H Li
- Division of Human Genetics; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
- Department of Pediatrics; University of Pennsylvania Perelman School of Medicine; Philadelphia Pennsylvania
| | - Kelly Arndt
- Department of Human Genetics; The University of Chicago; Chicago Illinois
| | - Soma Das
- Department of Human Genetics; The University of Chicago; Chicago Illinois
| | - Elliott M Weiss
- Department of Pediatrics; University of Pennsylvania Perelman School of Medicine; Philadelphia Pennsylvania
- Division of Neonatology; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
- Department of Medical Ethics and Health Policy; University of Pennsylvania; Philadelphia Pennsylvania
| | - Yaning Wu
- Division of Human Genetics; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
| | - Kriti Gwal
- Department of Radiology; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
| | - Karuna V Shekdar
- Department of Radiology; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
| | - Elaine H Zackai
- Division of Human Genetics; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
- Department of Pediatrics; University of Pennsylvania Perelman School of Medicine; Philadelphia Pennsylvania
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162
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Pulvers JN, Journiac N, Arai Y, Nardelli J. MCPH1: a window into brain development and evolution. Front Cell Neurosci 2015; 9:92. [PMID: 25870538 PMCID: PMC4376118 DOI: 10.3389/fncel.2015.00092] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/28/2015] [Indexed: 12/21/2022] Open
Abstract
The development of the mammalian cerebral cortex involves a series of mechanisms: from patterning, progenitor cell proliferation and differentiation, to neuronal migration. Many factors influence the development of the cerebral cortex to its normal size and neuronal composition. Of these, the mechanisms that influence the proliferation and differentiation of neural progenitor cells are of particular interest, as they may have the greatest consequence on brain size, not only during development but also in evolution. In this context, causative genes of human autosomal recessive primary microcephaly, such as ASPM and MCPH1, are attractive candidates, as many of them show positive selection during primate evolution. MCPH1 causes microcephaly in mice and humans and is involved in a diverse array of molecular functions beyond brain development, including DNA repair and chromosome condensation. Positive selection of MCPH1 in the primate lineage has led to much insight and discussion of its role in brain size evolution. In this review, we will present an overview of MCPH1 from these multiple angles, and whilst its specific role in brain size regulation during development and evolution remain elusive, the pieces of the puzzle will be discussed with the aim of putting together the full picture of this fascinating gene.
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Affiliation(s)
| | - Nathalie Journiac
- U1141 Inserm Paris, France ; Université Paris Diderot, Sorbonne Paris Cité, UMRS 1141 Paris, France
| | - Yoko Arai
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité Paris, France
| | - Jeannette Nardelli
- U1141 Inserm Paris, France ; Université Paris Diderot, Sorbonne Paris Cité, UMRS 1141 Paris, France
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163
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Bizzotto S, Francis F. Morphological and functional aspects of progenitors perturbed in cortical malformations. Front Cell Neurosci 2015; 9:30. [PMID: 25729350 PMCID: PMC4325918 DOI: 10.3389/fncel.2015.00030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Accepted: 01/18/2015] [Indexed: 11/13/2022] Open
Abstract
In this review, we discuss molecular and cellular mechanisms important for the function of neuronal progenitors during development, revealed by their perturbation in different cortical malformations. We focus on a class of neuronal progenitors, radial glial cells (RGCs), which are renowned for their unique morphological and behavioral characteristics, constituting a key element during the development of the mammalian cerebral cortex. We describe how the particular morphology of these cells is related to their roles in the orchestration of cortical development and their influence on other progenitor types and post-mitotic neurons. Important for disease mechanisms, we overview what is currently known about RGC cellular components, cytoskeletal mechanisms, signaling pathways and cell cycle characteristics, focusing on how defects lead to abnormal development and cortical malformation phenotypes. The multiple recent entry points from human genetics and animal models are contributing to our understanding of this important cell type. Combining data from phenotypes in the mouse reveals molecules which potentially act in common pathways. Going beyond this, we discuss future directions that may provide new data in this expanding area.
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Affiliation(s)
- Sara Bizzotto
- INSERM UMRS 839 Paris, France ; Sorbonne Universités, Université Pierre et Marie Curie Paris, France ; Institut du Fer à Moulin Paris, France
| | - Fiona Francis
- INSERM UMRS 839 Paris, France ; Sorbonne Universités, Université Pierre et Marie Curie Paris, France ; Institut du Fer à Moulin Paris, France
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164
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Faheem M, Naseer MI, Rasool M, Chaudhary AG, Kumosani TA, Ilyas AM, Pushparaj P, Ahmed F, Algahtani HA, Al-Qahtani MH, Saleh Jamal H. Molecular genetics of human primary microcephaly: an overview. BMC Med Genomics 2015; 8 Suppl 1:S4. [PMID: 25951892 PMCID: PMC4315316 DOI: 10.1186/1755-8794-8-s1-s4] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder that is characterised by microcephaly present at birth and non-progressive mental retardation. Microcephaly is the outcome of a smaller but architecturally normal brain; the cerebral cortex exhibits a significant decrease in size. MCPH is a neurogenic mitotic disorder, though affected patients demonstrate normal neuronal migration, neuronal apoptosis and neural function. Twelve MCPH loci (MCPH1-MCPH12) have been mapped to date from various populations around the world and contain the following genes: Microcephalin, WDR62, CDK5RAP2, CASC5, ASPM, CENPJ, STIL, CEP135, CEP152, ZNF335, PHC1 and CDK6. It is predicted that MCPH gene mutations may lead to the disease phenotype due to a disturbed mitotic spindle orientation, premature chromosomal condensation, signalling response as a result of damaged DNA, microtubule dynamics, transcriptional control or a few other hidden centrosomal mechanisms that can regulate the number of neurons produced by neuronal precursor cells. Additional findings have further elucidated the microcephaly aetiology and pathophysiology, which has informed the clinical management of families suffering from MCPH. The provision of molecular diagnosis and genetic counselling may help to decrease the frequency of this disorder.
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165
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Molecular and cellular basis of autosomal recessive primary microcephaly. BIOMED RESEARCH INTERNATIONAL 2014; 2014:547986. [PMID: 25548773 PMCID: PMC4274849 DOI: 10.1155/2014/547986] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 09/18/2014] [Accepted: 09/18/2014] [Indexed: 01/23/2023]
Abstract
Autosomal recessive primary microcephaly (MCPH) is a rare hereditary neurodevelopmental disorder characterized by a marked reduction in brain size and intellectual disability. MCPH is genetically heterogeneous and can exhibit additional clinical features that overlap with related disorders including Seckel syndrome, Meier-Gorlin syndrome, and microcephalic osteodysplastic dwarfism. In this review, we discuss the key proteins mutated in MCPH. To date, MCPH-causing mutations have been identified in twelve different genes, many of which encode proteins that are involved in cell cycle regulation or are present at the centrosome, an organelle crucial for mitotic spindle assembly and cell division. We highlight recent findings on MCPH proteins with regard to their role in cell cycle progression, centrosome function, and early brain development.
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167
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Cortical neurogenesis in the absence of centrioles. Nat Neurosci 2014; 17:1528-35. [PMID: 25282615 PMCID: PMC4213237 DOI: 10.1038/nn.3831] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 09/09/2014] [Indexed: 12/14/2022]
Abstract
Neuronal production in the mammalian cortex depends on extensive mitoses of radial glial progenitors (RGPs) residing in the ventricular zone (VZ). Here, we examine the function of centrioles in RGPs during cortical neurogenesis in mice by conditional removal of SAS-4, a protein required for centriole biogenesis. SAS-4 deletion leads to a progressive loss of centrioles, accompanied by RGP detachment from the VZ. Delocalized RGPs do not become outer subventricular zone RGPs (oRGs). While remaining proliferative, ectopic RGPs, as well as those in the VZ with a centrosomal deficit exhibit prolonged mitosis, p53 up-regulation and apoptosis, resulting in neuronal loss and microcephaly. Simultaneous removal of p53 fully rescues RGP death and microcephaly, but not RGP delocalization and randomized mitotic spindle orientation. Our findings define centriolar functions in anchoring RGPs in the VZ and ensuring their efficient mitoses, and also reveal the remarkable adaptability of RGPs in the developing cortex.
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168
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Abstract
In the past few years, the increasing accessibility of next-generation sequencing technology has translated to a number of significant advances in our understanding of brain malformations. Genes causing brain malformations, previously intractable due to their complex presentation, rarity, sporadic occurrence, or molecular mechanism, are being identified at an unprecedented rate and are revealing important insights into central nervous system development. Recent discoveries highlight new associations of biological processes with human disease including the PI3K-AKT-mTOR pathway in brain overgrowth syndromes, the trafficking of cellular proteins in microcephaly-capillary malformation syndrome, and the role of the exosome in the etiology of pontocerebellar hypoplasia. Several other gene discoveries expand our understanding of the role of mitosis in the primary microcephaly syndromes and post-translational modification of dystroglycan in lissencephaly. Insights into polymicrogyria and heterotopias show us that these 2 malformations are complex in their etiology, while recent work in holoprosencephaly and Dandy-Walker malformation suggest that, at least in some instances, the development of these malformations requires "multiple-hits" in the sonic hedgehog pathway. The discovery of additional genes for primary microcephaly, pontocerebellar hypoplasia, and spinocerebellar ataxia continue to impress upon us the significant degree of genetic heterogeneity associated with many brain malformations. It is becoming increasingly evident that next-generation sequencing is emerging as a tool to facilitate rapid and cost-effective molecular diagnoses that will be translated into routine clinical care for these rare conditions in the near future.
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169
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Fujimori A, Itoh K, Goto S, Hirakawa H, Wang B, Kokubo T, Kito S, Tsukamoto S, Fushiki S. Disruption of Aspm causes microcephaly with abnormal neuronal differentiation. Brain Dev 2014; 36:661-9. [PMID: 24220505 DOI: 10.1016/j.braindev.2013.10.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 10/11/2013] [Accepted: 10/13/2013] [Indexed: 10/26/2022]
Abstract
AIMS A number of ASPM mutations have been detected in primary microcephaly patients. In order to evaluate the function of ASPM in brain development, we generated model animals of human autosomal recessive primary microcephaly-5 (MCPH5). METHODS In the Aspm knock-out mice, the exon 2-3 of the Aspm gene was encompassed by a pair of loxP signals so that cre-recombinase activity switched the allele from wild-type to null zygotes as frequently, as expected from the Mendelian inheritance. We precisely analyzed the brains of adults and fetuses using immunohistochemistry and morphometry. RESULTS The adult brains of the Aspm(-/-) mice were smaller, especially in the cerebrum. In the barrel field of the somatosensory cortex, layer I was significantly thicker, whereas layer VI was significantly thinner in Aspm(-/-) mice, compared with Aspm(+/+) mice. The total number of cells and the thickness of the cortical plate at embryonic day 16.5 was significantly decreased in Aspm(-/-) mice, compared with Aspm(+/+) mice. Furthermore, the expression of transcription factors, such as Tbr1 and Satb2, was significantly increased in the subplate of the Aspm(-/-) mice. CONCLUSIONS The results suggested that Aspm is essential to the proliferation and differentiation of neural stem/progenitor cells. The Aspm gene loss model provided a novel pathogenetic insight into acquired microcephaly, which can be caused by in utero exposure to both known and unknown teratogens.
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Affiliation(s)
- Akira Fujimori
- Heavy-Ion Radiobiology Research Group, Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
| | - Kyoko Itoh
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
| | - Shoko Goto
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Hirokazu Hirakawa
- Heavy-Ion Radiobiology Research Group, Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
| | - Bing Wang
- Heavy-Ion Radiobiology Research Group, Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
| | - Toshiaki Kokubo
- Heavy-Ion Radiobiology Research Group, Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
| | - Seiji Kito
- Heavy-Ion Radiobiology Research Group, Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
| | - Satoshi Tsukamoto
- Heavy-Ion Radiobiology Research Group, Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
| | - Shinji Fushiki
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
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170
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Simplified gyral pattern in severe developmental microcephalies? New insights from allometric modeling for spatial and spectral analysis of gyrification. Neuroimage 2014; 102 Pt 2:317-31. [PMID: 25107856 DOI: 10.1016/j.neuroimage.2014.07.057] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 07/28/2014] [Accepted: 07/28/2014] [Indexed: 01/13/2023] Open
Abstract
The strong positive-allometric relationship between brain size, cortical extension and gyrification complexity, recently highlighted in the general population, could be modified by brain developmental disorders. Indeed, in case of brain growth insufficiency, the pathophysiological relevance of the "simplified gyral pattern" phenotype is strongly disputed since almost no genotype-phenotype correlations have been found in primary microcephalies. Using surface scaling analysis and newly-developed spectral analysis of gyrification (Spangy), we tested whether the gyral simplification in groups of severe microcephalies related to ASPM, PQBP1 or fetal-alcohol-syndrome could be fully explained by brain size reduction according to the allometric scaling law established in typically-developing control groups, or whether an additional disease effect was to be suspected. We found the surface area reductions to be fully explained by scaling effect, leading to predictable folding intensities measured by gyrification indices. As for folding pattern assessed by spectral analysis, scaling effect also accounted for the majority of the variations, but an additional negative or positive disease effect was found in the case of ASPM and PQBP1-linked microcephalies, respectively. Our results point out the necessity of taking allometric scaling into account when studying the gyrification variability in pathological conditions. They also show that the quantitative analysis of gyrification complexity through spectral analysis can enable distinguishing between even (predictable, non-specific) and uneven (unpredictable, maybe disease-specific) gyral simplifications.
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171
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Taverna E, Götz M, Huttner WB. The cell biology of neurogenesis: toward an understanding of the development and evolution of the neocortex. Annu Rev Cell Dev Biol 2014; 30:465-502. [PMID: 25000993 DOI: 10.1146/annurev-cellbio-101011-155801] [Citation(s) in RCA: 489] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Neural stem and progenitor cells have a central role in the development and evolution of the mammalian neocortex. In this review, we first provide a set of criteria to classify the various types of cortical stem and progenitor cells. We then discuss the issue of cell polarity, as well as specific subcellular features of these cells that are relevant for their modes of division and daughter cell fate. In addition, cortical stem and progenitor cell behavior is placed into a tissue context, with consideration of extracellular signals and cell-cell interactions. Finally, the differences across species regarding cortical stem and progenitor cells are dissected to gain insight into key developmental and evolutionary mechanisms underlying neocortex expansion.
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Affiliation(s)
- Elena Taverna
- Max-Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany;
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172
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Hainline SG, Rickmyre JL, Neitzel LR, Lee LA, Lee E. The Drosophila MCPH1-B isoform is a substrate of the APCCdh1 E3 ubiquitin ligase complex. Biol Open 2014; 3:669-76. [PMID: 24972868 PMCID: PMC4154303 DOI: 10.1242/bio.20148318] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The Anaphase-Promoting Complex (APC) is a multi-subunit E3 ubiquitin ligase that coordinates progression through the cell cycle by temporally and spatially promoting the degradation of key proteins. Many of these targeted proteins have been shown to play important roles in regulating orderly progression through the cell cycle. Using a previously described Drosophila in vitro expression cloning approach, we screened for new substrates of the APC in Xenopus egg extract and identified Drosophila MCPH1 (dMCPH1), a protein encoded by the homolog of a causative gene for autosomal recessive primary microcephaly in humans. The dMCPH1-B splice form, but not the dMCPH1-C splice form, undergoes robust degradation in Xenopus interphase egg extract in a Cdh1-dependent manner. Degradation of dMCPH1-B is controlled by an N-terminal destruction box (D-box) motif as its deletion or mutation blocks dMCPH1-B degradation. dMCPH1 levels are increased in Drosophila morula (APC2) mutant embryos, consistent with dMCPH1 being an APC substrate in vivo. Using a purified, reconstituted system, we show that dMCPH1-B is ubiquitinated by APCCdh1, indicating that the effect of APC on dMCPH1-B ubiquitination and degradation is direct. Full-length human MCPH1 (hMCPH1) has been predicted to be an APC substrate based on its interaction with the APC subunit Cdc27. We were not able to detect changes in hMCPH1 levels during the cell cycle in cultured human cells. Overexpression of hMCPH1 (or dMCPH1-B) in developing Xenopus embryos, however, disrupts cell division, suggesting that proper regulation of hMCPH1 and dMCPH1-B activity plays a critical role in proper cell-cycle progression.
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Affiliation(s)
- Sarah G Hainline
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA Present address: Sarah Cannon Research Institute, Nashville, TN 37203, USA
| | - Jamie L Rickmyre
- Present address: Sarah Cannon Research Institute, Nashville, TN 37203, USA
| | - Leif R Neitzel
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA Present address: Sarah Cannon Research Institute, Nashville, TN 37203, USA
| | - Laura A Lee
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA Present address: Sarah Cannon Research Institute, Nashville, TN 37203, USA.
| | - Ethan Lee
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA Present address: Sarah Cannon Research Institute, Nashville, TN 37203, USA.
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173
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Khan MA, Rupp VM, Orpinell M, Hussain MS, Altmüller J, Steinmetz MO, Enzinger C, Thiele H, Höhne W, Nürnberg G, Baig SM, Ansar M, Nürnberg P, Vincent JB, Speicher MR, Gönczy P, Windpassinger C. A missense mutation in the PISA domain of HsSAS-6 causes autosomal recessive primary microcephaly in a large consanguineous Pakistani family. Hum Mol Genet 2014; 23:5940-9. [DOI: 10.1093/hmg/ddu318] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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174
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Enard W. Comparative genomics of brain size evolution. Front Hum Neurosci 2014; 8:345. [PMID: 24904382 PMCID: PMC4033227 DOI: 10.3389/fnhum.2014.00345] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 05/06/2014] [Indexed: 01/12/2023] Open
Abstract
Which genetic changes took place during mammalian, primate and human evolution to build a larger brain? To answer this question, one has to correlate genetic changes with brain size changes across a phylogeny. Such a comparative genomics approach provides unique information to better understand brain evolution and brain development. However, its statistical power is limited for example due to the limited number of species, the presumably complex genetics of brain size evolution and the large search space of mammalian genomes. Hence, it is crucial to add functional information, for example by limiting the search space to genes and regulatory elements known to play a role in the relevant cell types during brain development. Similarly, it is crucial to experimentally follow up on hypotheses generated by such a comparative approach. Recent progress in understanding the molecular and cellular mechanisms of mammalian brain development, in genome sequencing and in genome editing, promises to make a close integration of evolutionary and experimental methods a fruitful approach to better understand the genetics of mammalian brain size evolution.
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Affiliation(s)
- Wolfgang Enard
- Department of Biology II, Ludwig Maximilian University MunichMunich, Germany
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175
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Sun T, Hevner RF. Growth and folding of the mammalian cerebral cortex: from molecules to malformations. Nat Rev Neurosci 2014; 15:217-32. [PMID: 24646670 DOI: 10.1038/nrn3707] [Citation(s) in RCA: 325] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The size and extent of folding of the mammalian cerebral cortex are important factors that influence a species' cognitive abilities and sensorimotor skills. Studies in various animal models and in humans have provided insight into the mechanisms that regulate cortical growth and folding. Both protein-coding genes and microRNAs control cortical size, and recent progress in characterizing basal progenitor cells and the genes that regulate their proliferation has contributed to our understanding of cortical folding. Neurological disorders linked to disruptions in cortical growth and folding have been associated with novel neurogenetic mechanisms and aberrant signalling pathways, and these findings have changed concepts of brain evolution and may lead to new medical treatments for certain disorders.
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Affiliation(s)
- Tao Sun
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, BOX 60, New York, New York 10065, USA
| | - Robert F Hevner
- Department of Neurological Surgery and Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington 98101, USA
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176
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Zhang X, Ling J, Barcia G, Jing L, Wu J, Barry BJ, Mochida GH, Hill RS, Weimer JM, Stein Q, Poduri A, Partlow JN, Ville D, Dulac O, Yu TW, Lam ATN, Servattalab S, Rodriguez J, Boddaert N, Munnich A, Colleaux L, Zon LI, Söll D, Walsh CA, Nabbout R. Mutations in QARS, encoding glutaminyl-tRNA synthetase, cause progressive microcephaly, cerebral-cerebellar atrophy, and intractable seizures. Am J Hum Genet 2014; 94:547-58. [PMID: 24656866 DOI: 10.1016/j.ajhg.2014.03.003] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 03/05/2014] [Indexed: 01/30/2023] Open
Abstract
Progressive microcephaly is a heterogeneous condition with causes including mutations in genes encoding regulators of neuronal survival. Here, we report the identification of mutations in QARS (encoding glutaminyl-tRNA synthetase [QARS]) as the causative variants in two unrelated families affected by progressive microcephaly, severe seizures in infancy, atrophy of the cerebral cortex and cerebellar vermis, and mild atrophy of the cerebellar hemispheres. Whole-exome sequencing of individuals from each family independently identified compound-heterozygous mutations in QARS as the only candidate causative variants. QARS was highly expressed in the developing fetal human cerebral cortex in many cell types. The four QARS mutations altered highly conserved amino acids, and the aminoacylation activity of QARS was significantly impaired in mutant cell lines. Variants p.Gly45Val and p.Tyr57His were located in the N-terminal domain required for QARS interaction with proteins in the multisynthetase complex and potentially with glutamine tRNA, and recombinant QARS proteins bearing either substitution showed an over 10-fold reduction in aminoacylation activity. Conversely, variants p.Arg403Trp and p.Arg515Trp, each occurring in a different family, were located in the catalytic core and completely disrupted QARS aminoacylation activity in vitro. Furthermore, p.Arg403Trp and p.Arg515Trp rendered QARS less soluble, and p.Arg403Trp disrupted QARS-RARS (arginyl-tRNA synthetase 1) interaction. In zebrafish, homozygous qars loss of function caused decreased brain and eye size and extensive cell death in the brain. Our results highlight the importance of QARS during brain development and that epilepsy due to impairment of QARS activity is unusually severe in comparison to other aminoacyl-tRNA synthetase disorders.
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Affiliation(s)
- Xiaochang Zhang
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Jiqiang Ling
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA; Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Giulia Barcia
- Department of Pediatric Neurology, Centre de Reference Epilepsies Rares, Hôpital Necker-Enfants Malades, Assistance Publique-Hôpitaux de Paris, 75015 Paris, France; Institut National de la Santé et de la Recherche Médicale U1129, Université Paris Descartes, 75006 Paris, France; Institut National de la Santé et de la Recherche Médicale U1129, NeuroSpin, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, 91191 Gif-sur-Yvette, France
| | - Lili Jing
- Howard Hughes Medical Institute; Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Jiang Wu
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Brenda J Barry
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Ganeshwaran H Mochida
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, MA 02115, USA; Pediatric Neurology Unit, Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - R Sean Hill
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Jill M Weimer
- Sanford Children's Health Research Center, Sanford Research, 2301 East 60(th) Street North, Sioux Falls, SD 57104, USA
| | - Quinn Stein
- Departments of Pediatrics and Ob/Gyn, Sanford School of Medicine, Sioux Falls, SD 57105, USA
| | - Annapurna Poduri
- Department of Neurology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Jennifer N Partlow
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Dorothée Ville
- Department of Pediatric Neurology, Centre Hospitalier Universitaire de Lyon, 69007 Lyon, France
| | - Olivier Dulac
- Department of Pediatric Neurology, Centre de Reference Epilepsies Rares, Hôpital Necker-Enfants Malades, Assistance Publique-Hôpitaux de Paris, 75015 Paris, France; Institut National de la Santé et de la Recherche Médicale U1129, Université Paris Descartes, 75006 Paris, France; Institut National de la Santé et de la Recherche Médicale U1129, NeuroSpin, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, 91191 Gif-sur-Yvette, France
| | - Tim W Yu
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Department of Neurology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Anh-Thu N Lam
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Sarah Servattalab
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Jacqueline Rodriguez
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute
| | - Nathalie Boddaert
- Institut National de la Santé et de la Recherche Médicale U781, Department of Pediatric Radiology, Hôpital Necker-Enfants Malades, Imagine institute, Université Paris Descartes, 75006 Paris, France
| | - Arnold Munnich
- Institut National de la Santé et de la Recherche Médicale U781, Department of Genetics, Hôpital Necker-Enfants Malades, Imagine institute, Université Paris Descartes, 75006 Paris, France
| | - Laurence Colleaux
- Institut National de la Santé et de la Recherche Médicale U781, Department of Genetics, Hôpital Necker-Enfants Malades, Imagine institute, Université Paris Descartes, 75006 Paris, France
| | - Leonard I Zon
- Howard Hughes Medical Institute; Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
| | - Christopher A Walsh
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Howard Hughes Medical Institute; Department of Pediatrics, Harvard Medical School, MA 02115, USA; Department of Neurology, Harvard Medical School, Boston, MA 02115, USA; Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA.
| | - Rima Nabbout
- Department of Pediatric Neurology, Centre de Reference Epilepsies Rares, Hôpital Necker-Enfants Malades, Assistance Publique-Hôpitaux de Paris, 75015 Paris, France; Institut National de la Santé et de la Recherche Médicale U1129, Université Paris Descartes, 75006 Paris, France; Institut National de la Santé et de la Recherche Médicale U1129, NeuroSpin, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, 91191 Gif-sur-Yvette, France.
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177
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Tan CA, Topper S, Ward Melver C, Stein J, Reeder A, Arndt K, Das S. The first case of CDK5RAP2-related primary microcephaly in a non-consanguineous patient identified by next generation sequencing. Brain Dev 2014; 36:351-5. [PMID: 23726037 DOI: 10.1016/j.braindev.2013.05.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 04/30/2013] [Accepted: 05/02/2013] [Indexed: 11/17/2022]
Abstract
Primary autosomal recessive microcephaly (MCPH) is a genetically heterogeneous condition characterized by congenital microcephaly and intellectual disability. To date, 10 MCPH loci have been identified and due to the genetic heterogeneity of this condition, molecular testing for MCPH can be complicated. Our methods involved employing a next generation sequencing panel of MCPH-related genes allowing for the evaluation of multiple disease loci simultaneously. Next generation sequencing analysis of a 6 year old female with primary microcephaly identified novel compound heterozygous mutations (c.524_528del and c.4005-1G>A) in the CDK5RAP2 gene. A review of the published literature to date reveals that only three mutations have been previously reported in the CDK5RAP2 gene in the homozygous state in three Northern Pakistani and one Somali consanguineous MCPH families. Our patient represents the first non-consanguineous Caucasian individual to have been identified with CDK5RAP2-related MCPH. As only a handful of patients have been reported in the literature with CDK5RAP2-related MCPH, we anticipate the identification of individuals with CDK5RAP2 mutations from all ethnic backgrounds will continue. Our patient contributes to the ethnic and genotypic spectrum of CDK5RAP2-related MCPH and supports the occurrence of this genetic condition beyond that of consanguineous families of certain ethnic populations. Our results also highlight the utility of multi-gene sequencing panels to elucidate the etiology of genetically heterogeneous conditions.
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Affiliation(s)
- Christopher A Tan
- Department of Human Genetics, University of Chicago, 5841 S. Maryland Ave, MC 0077, Chicago, IL 60637, USA.
| | - Scott Topper
- Department of Human Genetics, University of Chicago, 5841 S. Maryland Ave, MC 0077, Chicago, IL 60637, USA
| | - Catherine Ward Melver
- Division of Medical Genetics, Akron Children's Hospital, One Perkins Square, Akron, OH 44308, USA
| | - Jennifer Stein
- Division of Medical Genetics, Akron Children's Hospital, One Perkins Square, Akron, OH 44308, USA
| | - Amanda Reeder
- Department of Human Genetics, University of Chicago, 5841 S. Maryland Ave, MC 0077, Chicago, IL 60637, USA
| | - Kelly Arndt
- Department of Human Genetics, University of Chicago, 5841 S. Maryland Ave, MC 0077, Chicago, IL 60637, USA
| | - Soma Das
- Department of Human Genetics, University of Chicago, 5841 S. Maryland Ave, MC 0077, Chicago, IL 60637, USA
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Adissu HA, Estabel J, Sunter D, Tuck E, Hooks Y, Carragher DM, Clarke K, Karp NA, Newbigging S, Jones N, Morikawa L, White JK, McKerlie C. Histopathology reveals correlative and unique phenotypes in a high-throughput mouse phenotyping screen. Dis Model Mech 2014; 7:515-24. [PMID: 24652767 PMCID: PMC4007403 DOI: 10.1242/dmm.015263] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The Mouse Genetics Project (MGP) at the Wellcome Trust Sanger Institute aims to generate and phenotype over 800 genetically modified mouse lines over the next 5 years to gain a better understanding of mammalian gene function and provide an invaluable resource to the scientific community for follow-up studies. Phenotyping includes the generation of a standardized biobank of paraffin-embedded tissues for each mouse line, but histopathology is not routinely performed. In collaboration with the Pathology Core of the Centre for Modeling Human Disease (CMHD) we report the utility of histopathology in a high-throughput primary phenotyping screen. Histopathology was assessed in an unbiased selection of 50 mouse lines with (n=30) or without (n=20) clinical phenotypes detected by the standard MGP primary phenotyping screen. Our findings revealed that histopathology added correlating morphological data in 19 of 30 lines (63.3%) in which the primary screen detected a phenotype. In addition, seven of the 50 lines (14%) presented significant histopathology findings that were not associated with or predicted by the standard primary screen. Three of these seven lines had no clinical phenotype detected by the standard primary screen. Incidental and strain-associated background lesions were present in all mutant lines with good concordance to wild-type controls. These findings demonstrate the complementary and unique contribution of histopathology to high-throughput primary phenotyping of mutant mice.
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Affiliation(s)
- Hibret A Adissu
- Centre for Modeling Human Disease, Toronto Centre for Phenogenomics, 25 Orde Street, Toronto, ON M5T 3H7, Canada
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179
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McDonell LM, Warman Chardon J, Schwartzentruber J, Foster D, Beaulieu CL, Majewski J, Bulman DE, Boycott KM. The utility of exome sequencing for genetic diagnosis in a familial microcephaly epilepsy syndrome. BMC Neurol 2014; 14:22. [PMID: 24479948 PMCID: PMC3916514 DOI: 10.1186/1471-2377-14-22] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 01/22/2014] [Indexed: 11/30/2022] Open
Abstract
Background Despite remarkable advances in genetic testing, many adults with syndromic epilepsy remain without a molecular diagnosis. The challenge in providing genetic testing for this patient population lies in the extensive genetic heterogeneity associated with epilepsy. Even for the subset of epilepsy patients that present with a defining feature, such as microcephaly, the number of possible genes that would require interrogation by Sanger sequencing is extensive and often prohibitively expensive. Case presentation We report a family of French Canadian descent with four adult children affected with severe intellectual disability, epilepsy and microcephaly born to consanguineous parents and evaluated by the Genetics Service to provide informed genetic counseling to unaffected family members regarding possible recurrence risks. We used whole-exome sequencing (WES) of DNA from one affected sibling as a first-line diagnostic tool and compared the prioritization of variants using two strategies: 1) focusing on genes with homozygous variants; and, 2) focusing on genes associated with microcephaly. Both approaches prioritized the same homozygous novel frameshift mutation (p.Arg608Serfs*26) in WDR62, a gene known to cause autosomal recessive primary microcephaly. Sanger sequencing confirmed the presence of the homozygous mutation in the other three affected siblings. Conclusions WES and subsequent filtering of the rare variants in a single affected family member led to the rapid and cost-effective identification of a novel homozygous frameshift mutation in WDR62, thereby explaining the severe neurodevelopmental disorder in this family and facilitating genetic counseling. Our findings support WES as an effective first-line diagnostic tool in families presenting with rare genetically heterogeneous neurological disorders.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Kym M Boycott
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada.
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180
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Agha Z, Iqbal Z, Azam M, Siddique M, Willemsen MH, Kleefstra T, Zweier C, de Leeuw N, Qamar R, van Bokhoven H. A complex microcephaly syndrome in a Pakistani family associated with a novel missense mutation in RBBP8 and a heterozygous deletion in NRXN1. Gene 2014; 538:30-5. [PMID: 24440292 DOI: 10.1016/j.gene.2014.01.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 01/07/2014] [Accepted: 01/08/2014] [Indexed: 11/29/2022]
Abstract
We report on a consanguineous Pakistani family with a severe congenital microcephaly syndrome resembling the Seckel syndrome and Jawad syndrome. The affected individuals in this family were born to consanguineous parents of whom the mother presented with mild intellectual disability (ID), epilepsy and diabetes mellitus. The two living affected brothers presented with microcephaly, white matter disease of the brain, hyponychia, dysmorphic facial features with synophrys, epilepsy, diabetes mellitus and ID. Genotyping with a 250K SNP array in both affected brothers revealed an 18 MB homozygous region on chromosome 18 p11.21-q12.1 encompassing the SCKL2 locus of the Seckel and Jawad syndromes. Sequencing of the RBBP8 gene, underlying the Seckel and Jawad syndromes, identified the novel mutation c.919A>G, p.Arg307Gly, segregating in a recessive manner in the family. In addition, in the two affected brothers and their mother we have also found a heterozygous 607kb deletion, encompassing exons 13-19 of NRXN1. Bidirectional sequencing of the coding exons of NRXN1 did not reveal any other mutation on the other allele. It thus appears that the phenotype of the mildly affected mother can be explained by the NRXN1 deletion, whereas the more severe and complex microcephalic phenotype of the two affected brothers is due to the simultaneous deletion in NRXN1 and the homozygous missense mutation affecting RBBP8.
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Affiliation(s)
- Zehra Agha
- Department of Biosciences, Faculty of Science, COMSATS Institute of Information Technology, Islamabad, Pakistan; Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands
| | - Zafar Iqbal
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands
| | - Maleeha Azam
- Department of Biosciences, Faculty of Science, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | | | - Marjolein H Willemsen
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands
| | - Tjitske Kleefstra
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands
| | - Christiane Zweier
- Institute of Human Genetics, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Nicole de Leeuw
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands
| | - Raheel Qamar
- Department of Biosciences, Faculty of Science, COMSATS Institute of Information Technology, Islamabad, Pakistan; Al-Nafees Medical College & Hospital, Isra University, Islamabad, Pakistan
| | - Hans van Bokhoven
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands; Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behavior, Nijmegen, The Netherlands.
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181
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Abnormal centrosome and spindle morphology in a patient with autosomal recessive primary microcephaly type 2 due to compound heterozygous WDR62 gene mutation. Orphanet J Rare Dis 2013; 8:178. [PMID: 24228726 PMCID: PMC4225825 DOI: 10.1186/1750-1172-8-178] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 10/10/2013] [Indexed: 11/19/2022] Open
Abstract
Background Autosomal recessive primary microcephaly (MCPH) is a rare neurodevelopmental disease with severe microcephaly at birth due to a pronounced reduction in brain volume and intellectual disability. Biallelic mutations in the WD repeat-containing protein 62 gene WDR62 are the genetic cause of MCPH2. However, the exact underlying pathomechanism of MCPH2 remains to be clarified. Methods/results We characterized the clinical, radiological, and cellular features that add to the human MCPH2 phenotype. Exome sequencing followed by Sanger sequencing in a German family with two affected daughters with primary microcephaly revealed in the index patient the compound heterozygous mutations c.1313G>A (p.R438H) / c.2864-2867delACAG (p.D955Afs*112) of WDR62, the second of which is novel. Radiological examination displayed small frontal lobes, corpus callosum hypoplasia, simplified hippocampal gyration, and cerebellar hypoplasia. We investigated the cellular phenotype in patient-derived lymphoblastoid cells and compared it with that of healthy female controls. WDR62 expression in the patient’s immortalized lymphocytes was deranged, and mitotic spindle defects as well as abnormal centrosomal protein localization were apparent. Conclusion We propose that a disruption of centrosome integrity and/or spindle organization may play an important role in the development of microcephaly in MCPH2.
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182
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Kumar A, Rajendran V, Sethumadhavan R, Purohit R. CEP proteins: the knights of centrosome dynasty. PROTOPLASMA 2013; 250:965-983. [PMID: 23456457 DOI: 10.1007/s00709-013-0488-9] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 02/12/2013] [Indexed: 06/01/2023]
Abstract
Centrosome forms the backbone of cell cycle progression mechanism. Recent debates have occurred regarding the essentiality of centrosome in cell cycle regulation. CEP family protein is the active component of centrosome and plays a vital role in centriole biogenesis and cell cycle progression control. A total of 31 proteins have been categorized into CEP family protein category and many more are under candidate evaluation. Furthermore, by the recent advancements in genomics and proteomics researches, several new CEP proteins have also been characterized. Here we have summarized the importance of CEP family proteins and their regulation mechanism involved in proper cell cycle progression. Further, we have reviewed the detailed molecular mechanism behind the associated pathological phenotypes and the possible therapeutic approaches. Proteins such as CEP57, CEP63, CEP152, CEP164, and CEP215 have been extensively studied with a detailed description of their molecular mechanisms, which are among the primary targets for drug discovery. Moreover, CEP27, CEP55, CEP70, CEP110, CEP120, CEP135, CEP192, CEP250, CEP290, and CEP350 also seem promising for future drug discovery approaches. Since the overview implicates that the overall researches on CEP proteins are not yet able to present significant details required for effective therapeutics development, thus, it is timely to discuss the importance of future investigations in this field.
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Affiliation(s)
- Ambuj Kumar
- Bioinformatics Division, School of Bio Sciences and Technology, Vellore Institute of Technology University, Vellore, 632014, Tamil Nadu, India
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183
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Is LB1 diseased or modern? A review of the proposed pathologies. Gene 2013; 528:12-20. [DOI: 10.1016/j.gene.2013.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Revised: 06/05/2013] [Accepted: 06/08/2013] [Indexed: 11/21/2022]
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184
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Hussain MS, Baig SM, Neumann S, Peche VS, Szczepanski S, Nürnberg G, Tariq M, Jameel M, Khan TN, Fatima A, Malik NA, Ahmad I, Altmüller J, Frommolt P, Thiele H, Höhne W, Yigit G, Wollnik B, Neubauer BA, Nürnberg P, Noegel AA. CDK6 associates with the centrosome during mitosis and is mutated in a large Pakistani family with primary microcephaly. Hum Mol Genet 2013; 22:5199-214. [PMID: 23918663 DOI: 10.1093/hmg/ddt374] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Autosomal recessive primary microcephaly (MCPH) is characterized by reduced head circumference, reduction in the size of the cerebral cortex with otherwise grossly normal brain structure and variable intellectual disability. MCPH is caused by mutations of 11 different genes which code for proteins implicated in cell division and cell cycle regulation. We studied a consanguineous eight-generation family from Pakistan with ten microcephalic children using homozygosity mapping and found a new MCPH locus at HSA 7q21.11-q21.3. Sanger sequencing of the most relevant candidate genes in this region revealed a homozygous single nucleotide substitution c.589G>A in CDK6, which encodes cyclin-dependent kinase 6. The mutation changes a highly conserved alanine at position 197 into threonine (p.Ala197Thr). Post hoc whole-exome sequencing corroborated this mutation's identification as the causal variant. CDK6 is an important protein for the control of the cell cycle and differentiation of various cell types. We show here for the first time that CDK6 associates with the centrosome during mitosis; however, this was not observed in patient fibroblasts. Moreover, the mutant primary fibroblasts exhibited supernumerary centrosomes, disorganized microtubules and mitotic spindles, an increased centrosome nucleus distance, reduced cell proliferation and impaired cell motility and polarity. Upon ectopic expression of the mutant protein and knockdown of CDK6 through shRNA, we noted similar effects. We propose that the identified CDK6 mutation leads to reduced cell proliferation and impairs the correct functioning of the centrosome in microtubule organization and its positioning near the nucleus which are key determinants during neurogenesis.
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185
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186
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Baab KL, McNulty KP, Harvati K. Homo floresiensis contextualized: a geometric morphometric comparative analysis of fossil and pathological human samples. PLoS One 2013; 8:e69119. [PMID: 23874886 PMCID: PMC3707875 DOI: 10.1371/journal.pone.0069119] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 06/11/2013] [Indexed: 11/19/2022] Open
Abstract
The origin of hominins found on the remote Indonesian island of Flores remains highly contentious. These specimens may represent a new hominin species, Homo floresiensis, descended from a local population of Homo erectus or from an earlier (pre-H. erectus) migration of a small-bodied and small-brained hominin out of Africa. Alternatively, some workers suggest that some or all of the specimens recovered from Liang Bua are pathological members of a small-bodied modern human population. Pathological conditions proposed to explain their documented anatomical features include microcephaly, myxoedematous endemic hypothyroidism (“cretinism”) and Laron syndrome (primary growth hormone insensitivity). This study evaluates evolutionary and pathological hypotheses through comparative analysis of cranial morphology. Geometric morphometric analyses of landmark data show that the sole Flores cranium (LB1) is clearly distinct from healthy modern humans and from those exhibiting hypothyroidism and Laron syndrome. Modern human microcephalic specimens converge, to some extent, on crania of extinct species of Homo. However in the features that distinguish these two groups, LB1 consistently groups with fossil hominins and is most similar to H. erectus. Our study provides further support for recognizing the Flores hominins as a distinct species, H. floresiensis, whose affinities lie with archaic Homo.
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Affiliation(s)
- Karen L. Baab
- Department of Anthropology and Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail:
| | - Kieran P. McNulty
- Evolutionary Anthropology Laboratory and Department of Anthropology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Katerina Harvati
- Department of Early Prehistory and Quaternary Ecology, Senckenberg Center for Human Evolution and Paleoecology, Eberhard Karls University of Tübingen, Tübingen, Germany
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187
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Tan CA, del Gaudio D, Dempsey MA, Arndt K, Botes S, Reeder A, Das S. Analysis of ASPM in an ethnically diverse cohort of 400 patient samples: perspectives of the molecular diagnostic laboratory. Clin Genet 2013; 85:353-8. [PMID: 23611254 DOI: 10.1111/cge.12172] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 04/17/2013] [Accepted: 04/17/2013] [Indexed: 11/27/2022]
Abstract
Primary Autosomal Recessive Microcephaly (MCPH) is characterized by congenital microcephaly usually without additional clinical findings. The most common gene implicated in MCPH is ASPM and a large percentage of mutations described have been homozygous and in consanguineous families primarily of East Asian and Middle Eastern origin. ASPM sequencing was performed on 400 patients between the years 2009 and 2012. Seventy of the patient samples were also analyzed for copy number changes in the ASPM gene. Forty protein truncating mutations, including 29 novel mutations, were identified in 39 patients with MCPH. Approximately one third of patients were compound heterozygotes, indicative of non-consanguinity in these patients. In addition, 46 non-synonymous variants were identified and interpreted as variants of uncertain significance. No deletion/duplication in ASPM was identified in the patients analyzed. A wide ethnic distribution was observed, including the first reported patients with ASPM-related MCPH of Hispanic descent. Clinical information was collected for 26 of the ASPM-positive patients and 41 of the ASPM-negative patients. As more individuals are identified with MCPH, we anticipate that we will continue to identify ASPM mutation-positive patients from all ethnic origins supporting the occurrence of this genetic condition beyond that of consanguineous families of certain ethnic populations.
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Affiliation(s)
- C A Tan
- Department of Human Genetics, University of Chicago, Chicago, IL, USA
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188
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Marthiens V, Rujano MA, Pennetier C, Tessier S, Paul-Gilloteaux P, Basto R. Centrosome amplification causes microcephaly. Nat Cell Biol 2013; 15:731-40. [PMID: 23666084 DOI: 10.1038/ncb2746] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 04/04/2013] [Indexed: 12/13/2022]
Abstract
Centrosome amplification is a hallmark of human tumours. In flies, extra centrosomes cause spindle position defects that result in the expansion of the neural stem cell (NSC) pool and consequently in tumour formation. Here we investigated the consequences of centrosome amplification during mouse brain development and homeostasis. We show that centrosome amplification causes microcephaly due to inefficient clustering mechanisms, where NSCs divide in a multipolar fashion producing aneuploid cells that enter apoptosis. Importantly, we show that apoptosis inhibition causes the accumulation of highly aneuploid cells that lose their proliferative capacity and differentiate, thus depleting the pool of progenitors. Even if these conditions are not sufficient to halt brain development, they cause premature death due to tissue degeneration. Our results support an alternative concept to explain the etiology of microcephaly and show that centrosome amplification and aneuploidy can result in tissue degeneration rather than overproliferation and cancer.
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189
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Issa L, Mueller K, Seufert K, Kraemer N, Rosenkotter H, Ninnemann O, Buob M, Kaindl AM, Morris-Rosendahl DJ. Clinical and cellular features in patients with primary autosomal recessive microcephaly and a novel CDK5RAP2 mutation. Orphanet J Rare Dis 2013; 8:59. [PMID: 23587236 PMCID: PMC3639195 DOI: 10.1186/1750-1172-8-59] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Accepted: 03/29/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Primary autosomal recessive microcephaly (MCPH) is a rare neurodevelopmental disorder that results in severe microcephaly at birth with pronounced reduction in brain volume, particularly of the neocortex, simplified cortical gyration and intellectual disability. Homozygous mutations in the Cyclin-dependent kinase 5 regulatory subunit-associated protein 2 gene CDK5RAP2 are the cause of MCPH3. Despite considerable interest in MCPH as a model disorder for brain development, the underlying pathomechanism has not been definitively established and only four pedigrees with three CDK5RAP2 mutations have been reported. Specifically for MCPH3, no detailed radiological or histological descriptions exist. METHODS/RESULTS We sought to characterize the clinical and radiological features and pathological cellular processes that contribute to the human MCPH3 phenotype. Haplotype analysis using microsatellite markers around the MCPH1-7 and PNKP loci in an Italian family with two sons with primary microcephaly, revealed possible linkage to the MCPH3 locus. Sequencing of the coding exons and exon/intron splice junctions of the CDK5RAP2 gene identified homozygosity for the novel nonsense mutation, c.4441C > T (p.Arg1481*), in both affected sons. cMRI showed microcephaly, simplified gyral pattern and hypogenesis of the corpus callosum. The cellular phenotype was assessed in EBV-transformed lymphocyte cell lines established from the two affected sons and compared with healthy male controls. CDK5RAP2 protein levels were below detection level in immortalized lymphocytes from the patients. Moreover, mitotic spindle defects and disrupted γ-tubulin localization to the centrosome were apparent. CONCLUSION These results suggest that spindle defects and a disruption of centrosome integrity play an important role in the development of microcephaly in MCPH3.
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Affiliation(s)
- Lina Issa
- Institute of Cell Biology and Neurobiology, Charité University Medicine, Berlin, Germany
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190
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Chen J, Ingham N, Clare S, Raisen C, Vancollie VE, Ismail O, McIntyre RE, Tsang SH, Mahajan VB, Dougan G, Adams DJ, White JK, Steel KP. Mcph1-deficient mice reveal a role for MCPH1 in otitis media. PLoS One 2013; 8:e58156. [PMID: 23516444 PMCID: PMC3596415 DOI: 10.1371/journal.pone.0058156] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 01/31/2013] [Indexed: 12/20/2022] Open
Abstract
Otitis media is a common reason for hearing loss, especially in children. Otitis media is a multifactorial disease and environmental factors, anatomic dysmorphology and genetic predisposition can all contribute to its pathogenesis. However, the reasons for the variable susceptibility to otitis media are elusive. MCPH1 mutations cause primary microcephaly in humans. So far, no hearing impairment has been reported either in the MCPH1 patients or mouse models with Mcph1 deficiency. In this study, Mcph1-deficient (Mcph1tm1a/tm1a) mice were produced using embryonic stem cells with a targeted mutation by the Sanger Institute's Mouse Genetics Project. Auditory brainstem response measurements revealed that Mcph1tm1a/tm1a mice had mild to moderate hearing impairment with around 70% penetrance. We found otitis media with effusion in the hearing-impaired Mcph1tm1a/tm1a mice by anatomic and histological examinations. Expression of Mcph1 in the epithelial cells of middle ear cavities supported its involvement in the development of otitis media. Other defects of Mcph1tm1a/tm1a mice included small skull sizes, increased micronuclei in red blood cells, increased B cells and ocular abnormalities. These findings not only recapitulated the defects found in other Mcph1-deficient mice or MCPH1 patients, but also revealed an unexpected phenotype, otitis media with hearing impairment, which suggests Mcph1 is a new gene underlying genetic predisposition to otitis media.
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Affiliation(s)
- Jing Chen
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Neil Ingham
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Simon Clare
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Claire Raisen
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | | | - Ozama Ismail
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | | | - Stephen H. Tsang
- Edward S. Harkness Eye Institute, Columbia University, New York, New York, United States of America
| | - Vinit B. Mahajan
- Omics Laboratory, Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States of America
| | - Gordon Dougan
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - David J. Adams
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | | | - Karen P. Steel
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
- * E-mail:
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191
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Dediu D, Cysouw M. Some structural aspects of language are more stable than others: a comparison of seven methods. PLoS One 2013; 8:e55009. [PMID: 23383035 PMCID: PMC3557264 DOI: 10.1371/journal.pone.0055009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 12/18/2012] [Indexed: 11/26/2022] Open
Abstract
Understanding the patterns and causes of differential structural stability is an area of major interest for the study of language change and evolution. It is still debated whether structural features have intrinsic stabilities across language families and geographic areas, or if the processes governing their rate of change are completely dependent upon the specific context of a given language or language family. We conducted an extensive literature review and selected seven different approaches to conceptualising and estimating the stability of structural linguistic features, aiming at comparing them using the same dataset, the World Atlas of Language Structures. We found that, despite profound conceptual and empirical differences between these methods, they tend to agree in classifying some structural linguistic features as being more stable than others. This suggests that there are intrinsic properties of such structural features influencing their stability across methods, language families and geographic areas. This finding is a major step towards understanding the nature of structural linguistic features and their interaction with idiosyncratic, lineage- and area-specific factors during language change and evolution.
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Affiliation(s)
- Dan Dediu
- Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.
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192
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AKBARIAZAR E, EBRAHIMPOUR M, AKBARI S, ARZHANGHI S, ABEDINI SS, NAJMABADI H, KAHRIZI K. A Novel Deletion Mutation in ASPM Gene in an Iranian Family with Autosomal Recessive Primary Microcephaly. IRANIAN JOURNAL OF CHILD NEUROLOGY 2013; 7:23-30. [PMID: 24665293 PMCID: PMC3943041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 01/23/2013] [Accepted: 02/05/2013] [Indexed: 10/24/2022]
Abstract
OBJECTIVE Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental and genetically heterogeneous disorder with decreased head circumference due to the abnormality in fetal brain growth. To date, nine loci and nine genes responsible for the situation have been identified. Mutations in the ASPM gene (MCPH5) is the most common cause of MCPH. The ASPM gene with 28 exons is essential for normal mitotic spindle function in embryonic neuroblasts. MATERIALS & METHODS We have ascertained twenty-two consanguineous families with intellectual disability and different ethnic backgrounds from Iran. Ten out of twenty-two families showed primary microcephaly in clinical examination. We investigated MCPH5 locus using homozygosity mapping by microsatellite marker. RESULT Sequence analysis of exon 8 revealed a deletion of nucleotide (T) in donor site of splicing site of ASPM in one family. The remaining nine families were not linked to any of the known loci .More investigation will be needed to detect the causative defect in these families. CONCLUSION [corrected] We detected a novel mutation in the donor splicing site of exon 8 of the ASPM gene. This deletion mutation can alter the ASPM transcript leading to functional impairment of the gene product.
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Affiliation(s)
- Elinaz AKBARIAZAR
- Msc of human genetics, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | - Mohammad EBRAHIMPOUR
- Msc of human genetics, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | - Saeedeh AKBARI
- Msc of human genetics, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | - Sanaz ARZHANGHI
- Bsc in Nursing, Genetics Research Center, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | | | - Hossein NAJMABADI
- Professor of Molecular Biology, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
| | - Kimia KAHRIZI
- Professor of Medical Genetics, Genetics Research Center, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran
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193
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The interleukin 3 gene (IL3) contributes to human brain volume variation by regulating proliferation and survival of neural progenitors. PLoS One 2012; 7:e50375. [PMID: 23226269 PMCID: PMC3511536 DOI: 10.1371/journal.pone.0050375] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 10/18/2012] [Indexed: 02/01/2023] Open
Abstract
One of the most significant evolutionary changes underlying the highly developed cognitive abilities of humans is the greatly enlarged brain volume. In addition to being far greater than in most other species, the volume of the human brain exhibits extensive variation and distinct sexual dimorphism in the general population. However, little is known about the genetic mechanisms underlying normal variation as well as the observed sex difference in human brain volume. Here we show that interleukin-3 (IL3) is strongly associated with brain volume variation in four genetically divergent populations. We identified a sequence polymorphism (rs31480) in the IL3 promoter which alters the expression of IL3 by affecting the binding affinity of transcription factor SP1. Further analysis indicated that IL3 and its receptors are continuously expressed in the developing mouse brain, reaching highest levels at postnatal day 1–4. Furthermore, we found IL3 receptor alpha (IL3RA) was mainly expressed in neural progenitors and neurons, and IL3 could promote proliferation and survival of the neural progenitors. The expression level of IL3 thus played pivotal roles in the expansion and maintenance of the neural progenitor pool and the number of surviving neurons. Moreover, we found that IL3 activated both estrogen receptors, but estrogen didn’t directly regulate the expression of IL3. Our results demonstrate that genetic variation in the IL3 promoter regulates human brain volume and reveals novel roles of IL3 in regulating brain development.
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194
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Villanea FA, Perry GH, Gutiérrez-Espeleta GA, Dominy NJ. ASPM and the evolution of cerebral cortical size in a community of New World monkeys. PLoS One 2012; 7:e44928. [PMID: 23028686 PMCID: PMC3459963 DOI: 10.1371/journal.pone.0044928] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 08/10/2012] [Indexed: 11/25/2022] Open
Abstract
The ASPM (abnormal spindle-like microcephaly associated) gene has been proposed as a major determinant of cerebral cortical size among primates, including humans. Yet the specific functions of ASPM and its connection to human intelligence remain controversial. This debate is limited in part by a taxonomic focus on Old World monkeys and apes. Here we expand the comparative context of ASPM sequence analyses with a study of New World monkeys, a radiation of primates in which enlarged brain size has evolved in parallel in spider monkeys (genus Ateles) and capuchins (genus Cebus). The primate community of Costa Rica is perhaps a model system because it allows for independent pairwise comparisons of smaller- and larger-brained species within two taxonomic families. Accordingly, we analyzed the complete sequence of exon 18 of ASPM in Ateles geoffroyi, Alouatta palliata, Cebus capucinus, and Saimiri oerstedii. As the analysis of multiple species in a genus improves phylogenetic reconstruction, we also analyzed eleven published sequences from other New World monkeys. Our exon-wide, lineage-specific analysis of eleven genera and the ratio of rates of nonsynonymous to synonymous substitutions (dN/dS) on ASPM revealed no detectable evidence for positive selection in the lineages leading to Ateles or Cebus, as indicated by dN/dS ratios of <1.0 (0.6502 and 0.4268, respectively). Our results suggest that a multitude of interacting genes have driven the evolution of larger brains among primates, with different genes involved in this process in different encephalized lineages, or at least with evidence for positive selection not readily apparent for the same genes in all lineages. The primate community of Costa Rica may serve as a model system for future studies that aim to elucidate the molecular mechanisms underlying cognitive capacity and cortical size.
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Affiliation(s)
- Fernando A Villanea
- School of Biological Sciences, Washington State University, Pullman, Washington, United States of America.
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195
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Genin A, Desir J, Lambert N, Biervliet M, Van Der Aa N, Pierquin G, Killian A, Tosi M, Urbina M, Lefort A, Libert F, Pirson I, Abramowicz M. Kinetochore KMN network gene CASC5 mutated in primary microcephaly. Hum Mol Genet 2012; 21:5306-17. [PMID: 22983954 DOI: 10.1093/hmg/dds386] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Several genes expressed at the centrosome or spindle pole have been reported to underlie autosomal recessive primary microcephaly (MCPH), a neurodevelopmental disorder consisting of an important brain size reduction present since birth, associated with mild-to-moderate mental handicap and no other neurological feature nor associated malformation. Here, we report a mutation of CASC5 (aka Blinkin, or KNL1, or hSPC105) in MCPH patients from three consanguineous families, in one of which we initially reported the MCPH4 locus. The combined logarithm of odds score of the three families was >6. All patients shared a very rare homozygous mutation of CASC5. The mutation induced skipping of exon 18 with subsequent frameshift and truncation of the predicted protein. CASC5 is part of the KMN network of the kinetochore and is required for proper microtubule attachment to the chromosome centromere and for spindle-assembly checkpoint (SAC) activation during mitosis. Like MCPH gene ASPM, CASC5 is upregulated in the ventricular zone (VZ) of the human fetal brain. CASC5 binds BUB1, BUBR1, ZWINT-1 and interestingly it binds to MIS12 through a protein domain which is truncated by the mutation. CASC5 localized at the equatorial plate like ZWINT-1 and BUBR1, while ASPM, CEP152 and PCTN localized at the spindle poles in our patients and in controls. Comparison of primate and rodent lineages indicates accelerated evolution of CASC5 in the human lineage. Our data provide strong evidence for CASC5 as a novel MCPH gene, and underscore the role of kinetochore integrity in proper volumetric development of the human brain.
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Affiliation(s)
- Anne Genin
- Institute of Interdisciplinary Research IRIBHM , Université Libre de Bruxelles, Anderlecht, Belgium
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196
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Sajid Hussain M, Marriam Bakhtiar S, Farooq M, Anjum I, Janzen E, Reza Toliat M, Eiberg H, Kjaer KW, Tommerup N, Noegel AA, Nürnberg P, Baig SM, Hansen L. Genetic heterogeneity in Pakistani microcephaly families. Clin Genet 2012; 83:446-51. [DOI: 10.1111/j.1399-0004.2012.01932.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 07/04/2012] [Accepted: 07/04/2012] [Indexed: 01/01/2023]
Affiliation(s)
| | | | | | | | - E Janzen
- Cologne Center for Genomics (CCG); University of Cologne; Cologne; Germany
| | - M Reza Toliat
- Cologne Center for Genomics (CCG); University of Cologne; Cologne; Germany
| | - H Eiberg
- Wilhelm Johannsen Centre for Functional Genome Research, Department of Cellular and Molecular Medicine; University of Copenhagen; Copenhagen; Denmark
| | | | | | | | | | - SM Baig
- Human Molecular Genetics Laboratory, Health Biotechnology Division; National Institute for Biotechnology & Genetic Engineering (NIBGE); Faisalabad; Pakistan
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197
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Issa L, Kraemer N, Rickert CH, Sifringer M, Ninnemann O, Stoltenburg-Didinger G, Kaindl AM. CDK5RAP2 Expression During Murine and Human Brain Development Correlates with Pathology in Primary Autosomal Recessive Microcephaly. Cereb Cortex 2012; 23:2245-60. [DOI: 10.1093/cercor/bhs212] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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198
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Abstract
The centriole is an evolutionarily conserved macromolecular structure that is crucial for the formation of flagella, cilia and centrosomes. The ultrastructure of the centriole was first characterized decades ago with the advent of electron microscopy, revealing a striking ninefold radial arrangement of microtubules. However, it is only recently that the molecular mechanisms governing centriole assembly have begun to emerge, including the elucidation of the crucial role of spindle assembly abnormal 6 (SAS-6) proteins in imparting the ninefold symmetry. These advances have brought the field to an exciting era in which architecture meets function.
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199
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Ghani-Kakhki M, Robinson PN, Morlot S, Mitter D, Trimborn M, Albrecht B, Varon R, Sperling K, Neitzel H. Two Missense Mutations in the Primary Autosomal Recessive Microcephaly Gene MCPH1 Disrupt the Function of the Highly Conserved N-Terminal BRCT Domain of Microcephalin. Mol Syndromol 2012; 3:6-13. [PMID: 22855649 DOI: 10.1159/000338975] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2012] [Indexed: 12/23/2022] Open
Abstract
Primary microcephaly MCPH1 is an extremely rare autosomal recessive disorder associated with congenital microcephaly, mental retardation and a distinctive cellular phenotype of misregulated chromosome condensation. The MCPH1 gene encodes an 835-amino acid protein, microcephalin, which contains 1 N-terminal and 2 C-terminal BRCT (BRCA1 C-terminus) domains. BRCT domains are predominantly found in proteins involved in cell cycle control and DNA repair. Here we describe 1 novel and 1 previously reported MCPH1 missense mutation, p.Trp75Arg and p.Ser72Leu, respectively, in the N-terminal BRCT domain of microcephalin associated with severe congenital microcephaly. Both residues are entirely conserved in the MCPH1 orthologs of all vertebrate species and Drosophila. Proliferating lymphocytes of the patients with p.Trp75Arg and p.Ser72Leu show the unique cellular MCPH1 phenotype of misregulated chromosome condensation, indicating that these missense alterations disrupt the function of the N-terminal BRCT domain of the protein. Interestingly, both residues are strictly conserved in BRCT domains of BRCA1. ClustalW alignments show that the residue p.Ser72 of microcephalin corresponds to p.Ser1715 of the N-terminal BRCT domain of BRCA1, while the microcephalin residue p.Trp75 is analogous to p.Trp1718 in the N-terminal BRCT and to p.Trp1837 in C-terminal BRCT domains of BRCA1. Missense alterations for all 3 corresponding BRCA1 residues were described and are predicted to be deleterious resulting in the destabilization of the BRCA1 protein. Our data on the 2 MCPH1 missense alterations provide further evidence for the functional significance of these residues in BRCT domains.
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Affiliation(s)
- M Ghani-Kakhki
- Institute of Medical and Human Genetics, Charité - Universitätsmedizin Berlin, Berlin, Germany
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200
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Barkovich AJ, Guerrini R, Kuzniecky RI, Jackson GD, Dobyns WB. A developmental and genetic classification for malformations of cortical development: update 2012. Brain 2012; 135:1348-69. [PMID: 22427329 PMCID: PMC3338922 DOI: 10.1093/brain/aws019] [Citation(s) in RCA: 640] [Impact Index Per Article: 53.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Malformations of cerebral cortical development include a wide range of developmental disorders that are common causes of neurodevelopmental delay and epilepsy. In addition, study of these disorders contributes greatly to the understanding of normal brain development and its perturbations. The rapid recent evolution of molecular biology, genetics and imaging has resulted in an explosive increase in our knowledge of cerebral cortex development and in the number and types of malformations of cortical development that have been reported. These advances continue to modify our perception of these malformations. This review addresses recent changes in our perception of these disorders and proposes a modified classification based upon updates in our knowledge of cerebral cortical development.
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Affiliation(s)
- A James Barkovich
- Neuroradiology, University of California at San Francisco, 505 Parnassus Avenue, San Francisco, CA 94913-0628, USA.
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