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© 2009 American Academy of Neurology Chromosome 9p-linked families with frontotemporal dementia associated with motor neuron disease
Authors affiliations are listed at the end of the article. Address correspondence and reprint requests to Pr. Alexis Brice, CRicm-UMR675, Hôpital de la Pitié-Salpêtrière, 47, Boulevard de lHôpital, 75 651 Paris Cedex 13, France alexis.brice{at}upmc.fr Background: Frontotemporal dementia associated with motor neuron disease (FTD-MND) is a rare neurodegenerative disorder that may be inherited by autosomal dominant trait. No major gene has been identified but a locus was mapped on chromosome 9 (9p21.3-p13.3). Methods: Ten French families with FTD-MND were tested for linkage to the 9p21.3-p13.3 region. We report extensive mutation screening in 9p-linked families and their clinical characteristics. Results: We identified six new families with evidence for linkage to the chromosome 9p. Cumulative multipoint LOD score values were positive between markers D9S1121 and D9S301, reaching a peak of 8.0 at marker D9S248. Haplotype reconstruction defined the telomeric boundary at marker AFM218xg11, slightly narrowing the candidate interval. We found no disease-causing mutations by sequencing 29 candidate genes including IFT74 and no copy number variations in the 9p region. The mean age at onset was 57.9 ± 10.3 years (range, 41–84), with wide heterogeneity within and among families suggesting age-dependant penetrance. The patients presented isolated FTD (32%), isolated MND (29%), or both disorders (39%). The general characteristics of the disease did not differ, except for an older age at onset and shorter disease duration in the 9p-linked compared to nonlinked families. TDP-43-positive neuronal cytoplasmic inclusions were found in cortex and spinal cord in 3 patients. Conclusions: This study increases the number of 9p-linked families now reported and shows that this locus may have a major effect on frontotemporal dementia (FTD) and motor neuron disease (MND). Considering our results, the causative gene might be implicated in at least 60% of the families with FTD-MND disorder.
Abbreviations: BAT = BRLMM Analysis Tool; bvFTD = behavioral variant of frontotemporal dementia; FTD = frontotemporal dementia; MND = motor neuron disease; NCI = neuronal cytoplasmic inclusion; NII = neuronal intranuclear inclusions; SNP = single nucleotide polymorphism.
Supplemental data at www.neurology.org *These authors contributed equally.
Supported by France Alzheimer Association and ANR R06363DS (A.B.). Disclosure: The authors report no disclosures. Medical Devices: GeneChip mapping 250 K and 500 K assay (Affymetrix Inc., Santa Clara, CA). Received September 16, 2008. Accepted in final form February 12, 2009. This article has been cited by other articles:
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