Molecular subtyping of tumors from patients with familial glioma
Ruiz VY, Praska CE, Armstrong G, Kollmeyer TM, Yamada S, Decker PA, Kosel ML, Eckel-Passow JE, Lachance DH, Bainbridge MN, Melin BS, Bondy ML, Jenkins RB; Gliogene Consortium.
Neuro Oncol. 2018 May 18;20(6):810-817. doi: 10.1093/neuonc/nox192.
BACKGROUND: Single-gene mutation syndromes account for some familial glioma (FG); however, they make up only a small fraction of glioma families. Gliomas can be classified into 3 major molecular subtypes based on isocitrate dehydrogenase (IDH) mutation and 1p/19q codeletion. We hypothesized that the prevalence of molecular subtypes might differ in familial versus sporadic gliomas and that tumors in the same family should have the same molecular subtype.
METHODS: Participants in the FG study (Gliogene) provided samples for germline DNA analysis. Formalin-fixed, paraffin-embedded tumors were obtained from a subset of FG cases, and DNA was extracted. We analyzed tissue from 75 families, including 10 families containing a second affected family member. Copy number variation data were obtained using a first-generation Affymetrix molecular inversion probe (MIP) array.
RESULTS: Samples from 62 of 75 (83%) FG cases could be classified into the 3 subtypes. The prevalence of the molecular subtypes was: 30 (48%) IDH-wildtype, 21 (34%) IDH-mutant non-codeleted, and 11 (19%) IDH-mutant and 1p/19q codeleted. This distribution of molecular subtypes was not statistically different from that of sporadic gliomas (P = 0.54). Of 10 paired FG samples, molecular subtypes were concordant for 7 (κ = 0.59): 3 IDH-mutant non-codeleted, 2 IDH-wildtype, and 2 IDH-mutant and 1p/19q codeleted gliomas.
CONCLUSIONS: Our data suggest that within individual families, patients develop gliomas of the same molecular subtype. However, we did not observe differences in the prevalence of the molecular subtypes in FG compared with sporadic gliomas. These observations provide further insight into the distribution of molecular subtypes in FG.
October 18, 2017
Hypomorphic Recessive Variants in SUFU Impair the Sonic Hedgehog Pathway and Cause Joubert Syndrome with Cranio-facial and Skeletal Defects
De Mori R, Romani M, D’Arrigo S, Zaki MS, Lorefice E, Tardivo S, Biagini T, Stanley V, Musaev D, Fluss J, Micalizzi A, Nuovo S, Illi B, Chiapparini L, Di Marcotullio L, Issa MY, Anello D, Casella A, Ginevrino M, Leggins AS, Roosing S, Alfonsi R, Rosati J, Schot R, Mancini GMS, Bertini E, Dobyns WB, Mazza T, Gleeson JG, Valente EM.
Am J Hum Genet. 2017 Oct 5;101(4):552-563. doi: 10.1016/j.ajhg.2017.08.017. Epub 2017 Sep 28.
The Sonic Hedgehog (SHH) pathway is a key signaling pathway orchestrating embryonic development, mainly of the CNS and limbs. In vertebrates, SHH signaling is mediated by the primary cilium, and genetic defects affecting either SHH pathway members or ciliary proteins cause a spectrum of developmental disorders. SUFU is the main negative regulator of the SHH pathway and is essential during development. Indeed, Sufu knock-out is lethal in mice, and recessive pathogenic variants of this gene have never been reported in humans. Through whole-exome sequencing in subjects with Joubert syndrome, we identified four children from two unrelated families carrying homozygous missense variants in SUFU. The children presented congenital ataxia and cerebellar vermis hypoplasia with elongated superior cerebellar peduncles (mild “molar tooth sign”), typical cranio-facial dysmorphisms (hypertelorism, depressed nasal bridge, frontal bossing), and postaxial polydactyly. Two siblings also showed polymicrogyria. Molecular dynamics simulation predicted random movements of the mutated residues, with loss of the native enveloping movement of the binding site around its ligand GLI3. Functional studies on cellular models and fibroblasts showed that both variants significantly reduced SUFU stability and its capacity to bind GLI3 and promote its cleavage into the repressor form GLI3R. In turn, this impaired SUFU-mediated repression of the SHH pathway, as shown by altered expression levels of several target genes. We demonstrate that germline hypomorphic variants of SUFU cause deregulation of SHH signaling, resulting in recessive developmental defects of the CNS and limbs which share features with both SHH-related disorders and ciliopathies.
October 3, 2017
Low CSF 5-HIAA in Myoclonus Dystonia
Peall KJ, Ng J, Dy ME, Sharma N, Pope S, Heales S, Friedman JR, Kurian MA.
September 27, 2017
Homozygous Mutations in TBC1D23 Lead to a Non-degenerative Form of Pontocerebellar Hypoplasia
Marin-Valencia I, Gerondopoulos A, Zaki MS, Ben-Omran T, Almureikhi M, Demir E, Guemez-Gamboa A, Gregor A, Issa MY, Appelhof B, Roosing S, Musaev D, Rosti B, Wirth S, Stanley V, Baas F, Barr FA, Gleeson JG.
Am J Hum Genet. 2017 Sep 7;101(3):441-450. doi: 10.1016/j.ajhg.2017.07.015. Epub 2017 Aug 17.
Pontocerebellar hypoplasia (PCH) represents a group of recessive developmental disorders characterized by impaired growth of the pons and cerebellum, which frequently follows a degenerative course. Currently, there are 10 partially overlapping clinical subtypes and 13 genes known mutated in PCH. Here, we report biallelic TBC1D23 mutations in six individuals from four unrelated families manifesting a non-degenerative form of PCH. In addition to reduced volume of pons and cerebellum, affected individuals had microcephaly, psychomotor delay, and ataxia. In zebrafish, tbc1d23 morphants replicated the human phenotype showing hindbrain volume loss. TBC1D23 localized at the trans-Golgi and was regulated by the small GTPases Arl1 and Arl8, suggesting a role in trans-Golgi membrane trafficking. Altogether, this study provides a causative link between TBC1D23 mutations and PCH and suggests a less severe clinical course than other PCH subtypes.
August 22, 2017
Patient care standards for primary mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society
Parikh S, Goldstein A, Karaa A, Koenig MK, Anselm I, Brunel-Guitton C, Christodoulou J, Cohen BH, Dimmock D, Enns GM, Falk MJ, Feigenbaum A, Frye RE, Ganesh J, Griesemer D, Haas R, Horvath R, Korson M, Kruer MC, Mancuso M, McCormack S, Raboisson MJ, Reimschisel T, Salvarinova R, Saneto RP, Scaglia F, Shoffner J, Stacpoole PW, Sue CM, Tarnopolsky M, Van Karnebeek C, Wolfe LA, Cunningham ZZ, Rahman S, Chinnery PF.
Genet Med. 2017 Dec;19(12):10.1038/gim.2017.107. doi: 10.1038/gim.2017.107. Epub 2017 Jul 27.
The purpose of this statement is to provide consensus-based recommendations for optimal management and care for patients with primary mitochondrial disease. This statement is intended for physicians who are engaged in the diagnosis and management of these patients. Working group members were appointed by the Mitochondrial Medicine Society. The panel included members with several different areas of expertise. The panel members utilized surveys and the Delphi method to reach consensus. We anticipate that this statement will need to be updated as the field continues to evolve. Consensus-based recommendations are provided for the routine care and management of patients with primary genetic mitochondrial disease.
July 28, 2017
Analyses of SLC13A5-epilepsy patients reveal perturbations of TCA cycle.
Bainbridge MN, Cooney E, Miller M, Kennedy AD, Wulff JE, Donti T, Jhangiani SN, Gibbs RA, Elsea SH, Porter BE, Graham BH.
Mol Genet Metab. 2017 Aug;121(4):314-319. doi: 10.1016/j.ymgme.2017.06.009. Epub 2017 Jun 24. PMID: 28673551; PMCID: PMC7539367.
Objective: To interrogate the metabolic profile of five subjects from three families with rare, nonsense and missense mutations in SLC13A5 and Early Infantile Epileptic Encephalopathies (EIEE) characterized by severe, neonatal onset seizures, psychomotor retardation and global developmental delay.
Methods: Mass spectrometry of plasma, CSF and urine was used to identify consistently dysregulated analytes in our subjects.
Results: Distinctive elevations of citrate and dysregulation of citric acid cycle intermediates, supporting the hypothesis that loss of SLC13A5 function alters tricarboxylic acid cycle (TCA) metabolism and may disrupt metabolic compartmentation in the brain.
Significance: Our results indicate that analysis of plasma citrate and other TCA analytes in SLC13A5 deficient patients define a diagnostic metabolic signature that can aid in diagnosing children with this disease.
PMID: 28673551 | PMCID: PMC7539367 | DOI: 10.1016/j.ymgme.2017.06.009
June 24, 2017
A homozygous founder mutation in TRAPPC6B associates with a neurodevelopmental disorder characterised by microcephaly, epilepsy and autistic features
Marin-Valencia I, Novarino G, Johansen A, Rosti B, Issa MY, Musaev D, Bhat G, Scott E, Silhavy JL, Stanley V, Rosti RO, Gleeson JW, Imam FB, Zaki MS, Gleeson JG.
J Med Genet. 2018 Jan;55(1):48-54. doi: 10.1136/jmedgenet-2017-104627. Epub 2017 Jun 16.
BACKGROUND: Transport protein particle (TRAPP) is a multisubunit complex that regulates membrane trafficking through the Golgi apparatus. The clinical phenotype associated with mutations in various TRAPP subunits has allowed elucidation of their functions in specific tissues. The role of some subunits in human disease, however, has not been fully established, and their functions remain uncertain.
OBJECTIVE: We aimed to expand the range of neurodevelopmental disorders associated with mutations in TRAPP subunits by exome sequencing of consanguineous families.
METHODS: Linkage and homozygosity mapping and candidate gene analysis were used to identify homozygous mutations in families. Patient fibroblasts were used to study splicing defect and zebrafish to model the disease.
RESULTS: We identified six individuals from three unrelated families with a founder homozygous splice mutation in TRAPPC6B
, encoding a core subunit of the complex TRAPP I. Patients manifested a neurodevelopmental disorder characterised by microcephaly, epilepsy and autistic features, and showed splicing defect. Zebrafish trappc6b
morphants replicated the human phenotype, displaying decreased head size and neuronal hyperexcitability, leading to a lower seizure threshold.
CONCLUSION: This study provides clinical and functional evidence of the role of TRAPPC6B
in brain development and function.
June 20, 2017
Successful Application of Whole Genome Sequencing in a Medical Genetics Clinic
Bick D, Fraser PC, Gutzeit MF, Harris JM, Hambuch TM, Helbling DC, Jacob HJ, Kersten JN, Leuthner SR, May T, North PE, Prisco SZ, Schuler BA, Shimoyama M, Strong KA, Van Why SK, Veith R, Verbsky J, Weborg AM Jr, Wilk BM, Willoughby RE Jr, Worthey EA, Dimmock DP.
J Pediatr Genet. 2017 Jun;6(2):61-76. doi: 10.1055/s-0036-1593968. Epub 2016 Nov 28.
A pilot program was initiated using whole genome sequencing (WGS) to diagnose suspected genetic disorders in the Genetics Clinic at Children’s Hospital of Wisconsin. Twenty-two patients underwent WGS between 2010 and 2013. Initially, we obtained a 14% (3/22) diagnosis rate over 2 years; with subsequent reanalysis, this increased to 36% (8/22). Disease causing variants were identified in SKIV2L, CECR1, DGKE, PYCR2, RYR1, PDGFRB, EFTUD2, and BCS1L. In 75% (6/8) of diagnosed cases, the diagnosis affected treatment and/or medical surveillance. Additionally, one case demonstrated a homozygous A18V variant in VLDLR that appears to be associated with a previously undescribed phenotype.
May 13, 2017
Bedside Back to Bench: Building Bridges between Basic and Clinical Genomic Research
Manolio TA, Fowler DM, Starita LM, Haendel MA, MacArthur DG, Biesecker LG, Worthey E, Chisholm RL, Green ED, Jacob HJ, McLeod HL, Roden D, Rodriguez LL, Williams MS, Cooper GM, Cox NJ, Herman GE, Kingsmore S, Lo C, Lutz C, MacRae CA, Nussbaum RL, Ordovas JM, Ramos EM, Robinson PN, Rubinstein WS, Seidman C, Stranger BE, Wang H, Westerfield M, Bult C.
Cell. 2017 Mar 23;169(1):6-12. doi: 10.1016/j.cell.2017.03.005.
Genome sequencing has revolutionized the diagnosis of genetic diseases. Close collaborations between basic scientists and clinical genomicists are now needed to link genetic variants with disease causation. To facilitate such collaborations, we recommend prioritizing clinically relevant genes for functional studies, developing reference variant-phenotype databases, adopting phenotype description standards, and promoting data sharing.
March 25, 2017