@article {770, title = {MN1 C-terminal truncation syndrome is a novel neurodevelopmental and craniofacial disorder with partial rhombencephalosynapsis.}, journal = {Brain}, volume = {143}, year = {2020}, month = {2020 01 01}, pages = {55-68}, abstract = {

MN1 encodes a transcriptional co-regulator without homology to other proteins, previously implicated in acute myeloid leukaemia and development of the palate. Large deletions encompassing MN1 have been reported in individuals with variable neurodevelopmental anomalies and non-specific facial features. We identified a cluster of de novo truncating mutations in MN1 in a cohort of 23 individuals with strikingly similar dysmorphic facial features, especially midface hypoplasia, and intellectual disability with severe expressive language delay. Imaging revealed an atypical form of rhombencephalosynapsis, a distinctive brain malformation characterized by partial or complete loss of the cerebellar vermis with fusion of the cerebellar hemispheres, in 8/10 individuals. Rhombencephalosynapsis has no previously known definitive genetic or environmental causes. Other frequent features included perisylvian polymicrogyria, abnormal posterior clinoid processes and persistent trigeminal artery. MN1 is encoded by only two exons. All mutations, including the recurrent variant p.Arg1295* observed in 8/21 probands, fall in the terminal exon or the extreme 3{\textquoteright} region of exon 1, and are therefore predicted to result in escape from nonsense-mediated mRNA decay. This was confirmed in fibroblasts from three individuals. We propose that the condition described here, MN1 C-terminal truncation (MCTT) syndrome, is not due to MN1 haploinsufficiency but rather is the result of dominantly acting C-terminally truncated MN1 protein. Our data show that MN1 plays a critical role in human craniofacial and brain development, and opens the door to understanding the biological mechanisms underlying rhombencephalosynapsis.

}, keywords = {Abnormalities, Multiple, Adolescent, Basilar Artery, Carotid Arteries, Cerebellar Vermis, Cerebellum, Child, Child, Preschool, Cohort Studies, Comparative Genomic Hybridization, Craniofacial Abnormalities, Female, Fibroblasts, Humans, Imaging, Three-Dimensional, Infant, Intellectual Disability, Language Development Disorders, Magnetic Resonance Imaging, Male, Middle Aged, Mutation, Nervous System Malformations, Nonsense Mediated mRNA Decay, Polymicrogyria, Real-Time Polymerase Chain Reaction, RNA-Seq, Syndrome, Tomography, X-Ray Computed, Trans-Activators, Tumor Suppressor Proteins, Whole Exome Sequencing, Whole Genome Sequencing}, issn = {1460-2156}, doi = {10.1093/brain/awz379}, author = {Mak, Christopher C Y and Doherty, Dan and Lin, Angela E and Vegas, Nancy and Cho, Megan T and Viot, G{\'e}raldine and Dimartino, Cl{\'e}mantine and Weisfeld-Adams, James D and Lessel, Davor and Joss, Shelagh and Li, Chumei and Gonzaga-Jauregui, Claudia and Zarate, Yuri A and Ehmke, Nadja and Horn, Denise and Troyer, Caitlin and Kant, Sarina G and Lee, Youngha and Ishak, Gisele E and Leung, Gordon and Barone Pritchard, Amanda and Yang, Sandra and Bend, Eric G and Filippini, Francesca and Roadhouse, Chelsea and Lebrun, Nicolas and Mehaffey, Michele G and Martin, Pierre-Marie and Apple, Benjamin and Millan, Francisca and Puk, Oliver and Hoffer, Mariette J V and Henderson, Lindsay B and McGowan, Ruth and Wentzensen, Ingrid M and Pei, Steven and Zahir, Farah R and Yu, Mullin and Gibson, William T and Seman, Ann and Steeves, Marcie and Murrell, Jill R and Luettgen, Sabine and Francisco, Elizabeth and Strom, Tim M and Amlie-Wolf, Louise and Kaindl, Angela M and Wilson, William G and Halbach, Sara and Basel-Salmon, Lina and Lev-El, Noa and Denecke, Jonas and Vissers, Lisenka E L M and Radtke, Kelly and Chelly, Jamel and Zackai, Elaine and Friedman, Jan M and Bamshad, Michael J and Nickerson, Deborah A and Reid, Russell R and Devriendt, Koenraad and Chae, Jong-Hee and Stolerman, Elliot and McDougall, Carey and Powis, Z{\"o}e and Bienvenu, Thierry and Tan, Tiong Y and Orenstein, Naama and Dobyns, William B and Shieh, Joseph T and Choi, Murim and Waggoner, Darrel and Gripp, Karen W and Parker, Michael J and Stoler, Joan and Lyonnet, Stanislas and Cormier-Daire, Val{\'e}rie and Viskochil, David and Hoffman, Trevor L and Amiel, Jeanne and Chung, Brian H Y and Gordon, Christopher T} } @article {797, title = {A three-year follow-up study evaluating clinical utility of exome sequencing and diagnostic potential of reanalysis.}, journal = {NPJ Genom Med}, volume = {5}, year = {2020}, month = {2020}, pages = {37}, abstract = {

Exome sequencing (ES) has become one of the important diagnostic tools in clinical genetics with a reported diagnostic rate of 25-58\%. Many studies have illustrated the diagnostic and immediate clinical impact of ES. However, up to 75\% of individuals remain undiagnosed and there is scarce evidence supporting clinical utility beyond a follow-up period of >1 year. This is a 3-year follow-up analysis to our previous publication by Mak et al. ( 3:19, 2018), to evaluate the long-term clinical utility of ES and the diagnostic potential of exome reanalysis. The diagnostic yield of the initial study was 41\% (43/104). Exome reanalysis in 46 undiagnosed individuals has achieved 12 new diagnoses. The additional yield compared with the initial analysis was at least 12\% (increased from 41\% to at least 53\%). After a median follow-up period of 3.4 years, change in clinical management was observed in 72.2\% of the individuals (26/36), leading to positive change in clinical outcome in four individuals (11\%). There was a minimum healthcare cost saving of HKD$152,078 (USD$19,497; {\texteuro}17,282) annually for these four individuals. There were a total of six pregnancies from five families within the period. Prenatal diagnosis was performed in four pregnancies; one fetus was affected and resulted in termination. None of the parents underwent preimplantation genetic diagnosis. This 3-year follow-up study demonstrated the long-term clinical utility of ES at individual, familial and health system level, and the promising diagnostic potential of subsequent reanalysis. This highlights the benefits of implementing ES and regular reanalysis in the clinical setting.

}, issn = {2056-7944}, doi = {10.1038/s41525-020-00144-x}, author = {Fung, Jasmine L F and Yu, Mullin H C and Huang, Shushu and Chung, Claudia C Y and Chan, Marcus C Y and Pajusalu, Sander and Mak, Christopher C Y and Hui, Vivian C C and Tsang, Mandy H Y and Yeung, Kit San and Lek, Monkol and Chung, Brian H Y} } @article {685, title = {Redefining the Etiologic Landscape of Cerebellar Malformations.}, journal = {Am J Hum Genet}, volume = {105}, year = {2019}, month = {2019 Sep 05}, pages = {606-615}, abstract = {

Cerebellar malformations are diverse congenital anomalies frequently associated with developmental disability. Although genetic and prenatal non-genetic causes have been described, no systematic analysis has been performed. Here, we present a large-exome sequencing study of Dandy-Walker malformation (DWM) and cerebellar hypoplasia (CBLH). We performed exome sequencing in 282 individuals from 100 families with DWM or CBLH, and we established a molecular diagnosis in 36 of 100 families, with a significantly higher yield for CBLH (51\%) than for DWM (16\%). The 41 variants impact 27 neurodevelopmental-disorder-associated genes, thus demonstrating that CBLH and DWM are often features of monogenic neurodevelopmental disorders. Though only seven monogenic causes (19\%) were identified in more than one individual, neuroimaging review of 131 additional individuals confirmed cerebellar abnormalities in 23 of 27 genetic disorders (85\%). Prenatal risk factors were frequently found among individuals without a genetic diagnosis (30 of 64 individuals [47\%]). Single-cell RNA sequencing of prenatal human cerebellar tissue revealed gene enrichment in neuronal and vascular cell types; this suggests that defective vasculogenesis may disrupt cerebellar development. Further, de novo gain-of-function variants in PDGFRB, a tyrosine kinase receptor essential for vascular progenitor signaling, were associated with CBLH, and this discovery links genetic and non-genetic etiologies. Our results suggest that genetic defects impact specific cerebellar cell types and implicate abnormal vascular development as a mechanism for cerebellar malformations. We also confirmed a major contribution for non-genetic prenatal factors in individuals with cerebellar abnormalities, substantially influencing diagnostic evaluation and counseling regarding recurrence risk and prognosis.

}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2019.07.019}, author = {Aldinger, Kimberly A and Timms, Andrew E and Thomson, Zachary and Mirzaa, Ghayda M and Bennett, James T and Rosenberg, Alexander B and Roco, Charles M and Hirano, Matthew and Abidi, Fatima and Haldipur, Parthiv and Cheng, Chi V and Collins, Sarah and Park, Kaylee and Zeiger, Jordan and Overmann, Lynne M and Alkuraya, Fowzan S and Biesecker, Leslie G and Braddock, Stephen R and Cathey, Sara and Cho, Megan T and Chung, Brian H Y and Everman, David B and Zarate, Yuri A and Jones, Julie R and Schwartz, Charles E and Goldstein, Amy and Hopkin, Robert J and Krantz, Ian D and Ladda, Roger L and Leppig, Kathleen A and McGillivray, Barbara C and Sell, Susan and Wusik, Katherine and Gleeson, Joseph G and Nickerson, Deborah A and Bamshad, Michael J and Gerrelli, Dianne and Lisgo, Steven N and Seelig, Georg and Ishak, Gisele E and Barkovich, A James and Curry, Cynthia J and Glass, Ian A and Millen, Kathleen J and Doherty, Dan and Dobyns, William B} } @article {119, title = {Mechanisms for the Generation of Two Quadruplications Associated with Split-Hand Malformation.}, journal = {Hum Mutat}, volume = {37}, year = {2016}, month = {2016 Feb}, pages = {160-4}, abstract = {

Germline copy-number variants (CNVs) involving quadruplications are rare and the mechanisms generating them are largely unknown. Previously, we reported a 20-week gestation fetus with split-hand malformation; clinical microarray detected two maternally inherited triplications separated by a copy-number neutral region at 17p13.3, involving BHLHA9 and part of YWHAE. Here, we describe an 18-month-old male sibling of the previously described fetus with split-hand malformation. Custom high-density microarray and digital droplet PCR revealed the copy-number gains were actually quadruplications in the mother, the fetus, and her later born son. This quadruplication-normal-quadruplication pattern was shown to be expanded from the triplication-normal-triplication CNV at the same loci in the maternal grandmother. We mapped two breakpoint junctions and demonstrated that both are mediated by Alu repetitive elements and identical in these four individuals. We propose a three-step process combining Alu-mediated replicative-repair-based mechanism(s) and intergenerational, intrachromosomal nonallelic homologous recombination to generate the quadruplications in this family.

}, keywords = {14-3-3 Proteins, Adult, Aged, Alu Elements, Base Sequence, Basic Helix-Loop-Helix Transcription Factors, Chromosome Duplication, Chromosomes, Human, Pair 17, DNA Copy Number Variations, Female, Genetic Loci, Genome, Human, Hand Deformities, Congenital, Humans, Infant, Male, Molecular Sequence Data, Pedigree, Sequence Alignment, Sequence Analysis, DNA}, issn = {1098-1004}, doi = {10.1002/humu.22929}, author = {Gu, Shen and Posey, Jennifer E and Yuan, Bo and Carvalho, Claudia M B and Luk, H M and Erikson, Kelly and Lo, Ivan F M and Leung, Gordon K C and Pickering, Curtis R and Chung, Brian H Y and Lupski, James R} }