title: Hypermethylation of the CpG-island near the C9orf72 G₄C₂-repeat expansion in FTLD patients.
abstract: The G₄C₂-repeat expansion in C9orf72 is a common cause of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). C9orf72 transcription is reduced in expansion carriers implicating haploinsufficiency as one of the disease mechanisms. Indeed, our recent ALS study revealed that the expansion was associated with hypermethylation of the CpG-island (5'of the repeat) in DNA samples obtained from different tissues (blood, brain and spinal cord). However, the link between FTLD and methylation of the CpG-island is unknown. Hence, we investigated the methylation profile of the same CpG-island by bisulfite sequencing of DNA obtained from blood of 34 FTLD expansion carriers, 166 FTLD non-carriers and 103 controls. Methylation level was significantly higher in FTLD expansion carriers than non-carriers (P = 7.8E-13). Our results were confirmed by two methods (HhaI-assay and sequencing of cloned bisulfite PCR products). Hypermethylation occurred only in carriers of an allele with >50 repeats, and was not detected in non-carriers or individuals with an intermediate allele (22-43 repeats). As expected, the position/number of methylated CpGs was concordant between the sense and anti-sense DNA strand, suggesting that it is a stable epigenetic modification. Analysis of the combined ALS and FTLD datasets (82 expansion carriers) revealed that the degree of methylation of the entire CpG-island or contribution of specific CpGs (n = 26) is similar in both syndromes, with a trend towards a higher proportion of ALS patients with a high methylation level (P = 0.09). In conclusion, we demonstrated that hypermethylation of the CpG-island 5'of the G₄C₂-repeat is expansion-specific, but not syndrome-specific (ALS versus FTLD).
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8.
authors.forename: Zhengrui
authors.initials: Z
authors.lastname: Xi
authors.affiliation: Neurology I, Rita Levi Montalcini Department of Neuroscience, University of Torino, Torino, Italy.
authors.forename: Innocenzo
authors.initials: I
authors.lastname: Rainero
authors.affiliation: Neurology I, Rita Levi Montalcini Department of Neuroscience, University of Torino, Torino, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Rubino
authors.affiliation: Neurology I, Rita Levi Montalcini Department of Neuroscience, University of Torino, Torino, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Pinessi
authors.affiliation: Regional Neurogenetic Centre, Lamezia Terme, Azienda Sanitaria Provinciale Catanzaro, Catanzaro, Italy.
authors.forename: Amalia C
authors.initials: AC
authors.lastname: Bruni
authors.affiliation: Regional Neurogenetic Centre, Lamezia Terme, Azienda Sanitaria Provinciale Catanzaro, Catanzaro, Italy.
authors.forename: Raffaele G
authors.initials: RG
authors.lastname: Maletta
authors.affiliation: Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Nacmias
authors.affiliation: Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Sorbi
authors.affiliation: Neurology Unit, Department of Pathophysiology and Transplantation, University of Milan, Centro Dino Ferrari, Fondazione Ca' Granda, IRCCS Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Galimberti
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Laboratorio de Biología Molecular, Instituto de Investigaciones Neurológicas Dr. Raúl Carrea (FLENI), Buenos Aires, Argentina.
authors.forename: Ezequiel I
authors.initials: EI
authors.lastname: Surace
authors.affiliation: Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: Yonglan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8.
authors.forename: Danielle
authors.initials: D
authors.lastname: Moreno
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8.
authors.forename: Christine
authors.initials: C
authors.lastname: Sato
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liang
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8.
authors.forename: Janice
authors.initials: J
authors.lastname: Robertson
authors.affiliation: Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON, Canada M4N 3M5, Department of Medicine, Division of Neurology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8 and.
authors.forename: Lorne
authors.initials: L
authors.lastname: Zinman
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8, Department of Medicine, Division of Neurology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8 and.
authors.forename: Maria Carmela
authors.initials: MC
authors.lastname: Tartaglia
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8, Department of Medicine, Division of Neurology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8 and Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: St George-Hyslop
authors.affiliation: Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 60 Leonard Street, Toronto, Ontario, Canada M5T 2S8, Department of Medicine, Division of Neurology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8 and ekaterina.rogaeva@utoronto.ca.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Rogaeva
mesh_terms: D017668:Age of Onset; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics; D000073885:C9orf72 Protein; D018899:CpG Islands; D019175:DNA Methylation; D042622:DNA Repeat Expansion; D066264:Datasets as Topic; D005260:Female; D057174:Frontotemporal Lobar Degeneration / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D011506:Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D011506:Proteins