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Type: Journal article
Title: FMR2 expression in families with FRAXE mental retardation
Author: Gecz, J.
Oostra, B.
Hockey, A.
Carbonell, P.
Turner, G.
Haan, E.
Sutherland, G.
Mulley, J.
Citation: Human Molecular Genetics, 1997; 6(3):435-441
Issue Date: 1997
ISSN: 0964-6906
Statement of
Jozef Gécz, Ben A. Oostra, Athel Hockey, Pablo Carbonell, Gillian Turner, Eric A. Haan, Grant R. Sutherland, and John C. Mulley
Abstract: Normal individuals express the two alternative transcripts, FMR2 and Ox19, from the FRAXE-associated CpG island. Molecular analysis of the Ox19 transcript suggests that it is a truncated isoform of the FMR2 gene with an alternative 3′ end. Both isoforms showed a similar pattern of expression, with the Ox19 isoform expressed at a much lower level. Fibroblasts, chorionic villi and hair roots showed the highest level of FMR2 expression, whole blood cells and amniocytes showed very low expression, and the transcript was not detected in lymphoblasts. Fibroblasts of 11 individuals from seven families segregating FRAXE were assayed for FMR2 expression and FRAXE CpG island methylation. A man with an unmethylated expansion of 0.6 kb expressed FMR2 and represents a pre-mutation carrier. All chromosomes with FRAXE CCG expansions of 0.8 kb or greater were fully methylated and did not express the FMR2 gene, analogous to the mechanism of silencing the FMR1 gene in carriers of the FRAXA full mutation. The boundary between FRAXE pre-mutation and FRAXE full mutation is between 0.7 and 0.8 kb. Two men with absence of FMR2 expression in fibroblasts were not mentally impaired, suggesting that IQ in some men with FRAXE full mutation may remain within the normal range. Although molecular tools to study FRAXE non-specific mental retardation are now available, further psychometric and molecular studies are needed to characterize the effect of the FRAXE full mutation for the purpose of genetic counselling.
Keywords: Cells, Cultured
Fragile X Syndrome
RNA-Binding Proteins
Membrane Proteins
Nerve Tissue Proteins
Nuclear Proteins
RNA, Messenger
DNA Primers
Blotting, Northern
Blotting, Southern
Electrophoresis, Polyacrylamide Gel
Polymerase Chain Reaction
Sequence Analysis
Intelligence Tests
DNA Methylation
Gene Expression
Sequence Deletion
Base Sequence
CpG Islands
Polymorphism, Genetic
Molecular Sequence Data
Dosage Compensation, Genetic
Fragile X Mental Retardation Protein
Genetic Carrier Screening
Rights: © 1997 Oxford University Press
DOI: 10.1093/hmg/6.3.435
Published version:
Appears in Collections:Aurora harvest
Paediatrics publications

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