Nicola Halliwell

A hexanucleotide repeat expansion in C9ORF72 is the cause of chromosome 9p21-linked ALS-FTD

The chromosome 9p21 amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) locus contains one of the last major unidentified autosomal-dominant genes underlying these common neurodegenerative diseases. We have previously shown that a founder haplotype, covering the MOBKL2b, IFNK, and C9ORF72 genes, is present in the majority of cases linked to this region. Here we show that there is a large hexanucleotide (GGGGCC) repeat expansion in the first intron of C9ORF72 on the affected haplotype. This repeat expansion segregates perfectly with disease in the Finnish population, underlying 46.0% of familial ALS and 21.1% of sporadic ALS in that population. Taken together with the D90A SOD1 mutation, 87% of familial ALS in Finland is now explained by a simple monogenic cause. The repeat expansion is also present in one-third of familial ALS cases of outbred European descent, making it the most common genetic cause of these fatal neurodegenerative diseases identified to date.

Frontotemporal lobar degeneration genome wide association study replication confirms a risk locus shared with amyotrophic lateral sclerosis

Frontotemporal lobar degeneration (FTLD) is a common cause of dementia especially in patients under the age of 65. FTLD has a high incidence of heritability with as many as 40% of patients reporting a family history of disease. Recently, the first genome wide association study was performed using only FTLD patients with a pathologically confirmed TDP-43 pathology. Genome wide significance was detected for a single gene (TMEM106B) on chromosome 7, though several other loci on chromosomes 1, 8, 9, 10 and 11 reached nominal significance. Here we have undertaken an attempt to replicate the association of these loci in FTLD cohorts of British origin. We failed to detect any association of TMEM106B in the Manchester or London cohort either when analyzed individually or when combined. Genotyping of the Manchester cohort failed to replicate any of the loci on chromosome 1, 8 and 10 but did detect association of the single SNP (rs2015747) on chromosome 11. Association was also observed in the London cohort but in the opposite direction. Combining the 2 datasets yielded no association. Analysis of the chromosome 9 locus, revealed strong association in the London FTLD cohort and the Manchester FTLD+ALS cases. These data confirm that FTLD and amyotrophic lateral sclerosis (ALS) share a common genetic risk factor on chromosome 9p.

Analysis of the hexanucleotide repeat in C9ORF72 in Alzheimer's disease.

Frontotemporal lobar degeneration (FTLD) is a highly familial neurodegenerative disease. It has recently been shown that the most common genetic cause of FTLD and amyotrophic lateral sclerosis (ALS) is a hexanucleotide repeat expansion in C9ORF72. To investigate whether this expansion was specific to the FTLD/ALS disease spectrum, we genotyped the hexanucleotide repeat region of C9ORF72 in a large cohort of patients with Alzheimers disease (AD). A normal range of repeats was found in all cases. We conclude that the hexanucleotide repeat expansion is specific to the FTLD/ALS disease spectrum.

Ubiquitin associated protein 1 is a risk factor for frontotemporal lobar degeneration.

Frontotemporal lobar degeneration (FTLD) is now recognised as a common form of early onset dementia. Up to 40% of patients have a family history of disease demonstrating a large genetic component to its etiology. Linkage to chromosome 9p21 has recently been reported in families with this disorder. We undertook a large scale two-stage linkage disequilibrium mapping approach of this region in the Manchester FTLD cohort. We identified association of ubiquitin associated protein 1 (UBAP1; OR 1.42 95% CI 1.08-1.88, P=0.013) with FTLD in this cohort and we replicated this finding in an additional two independent cohorts from the Netherlands (OR 1.33 95% CI 1.04-1.69, P=0.022), the USA (OR 1.4 95% CI 1.02-1.92, P=0.032) and a forth Spanish cohort approached significant association (OR 1.45 95% CI 0.97-2.17, P=0.064). However, we failed to replicate in a fifth cohort from London (OR 0.99 95% CI 0.72-1.37, P=0.989). Quantitative analysis of UBAP1 mRNA extracted from tissue from the Manchester cases demonstrated a significant reduction of expression from the disease-associated haplotype. In addition, we identified a case of familial FTLD that demonstrated colocalisation of UBAP1 and TDP-43 in the neuronal cytoplasmic inclusions in the brain of this individual. Our data for the first time identifies UBAP1 as a genetic risk factor for FTLD and suggests a mechanistic relationship between this protein and TDP-43.

Analysis of optineurin in frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) can occur jointly with amyotrophic lateral sclerosis (ALS), and these 2 conditions share a genetic risk factor on chromosome 9. It has been reported that mutations in optineurin (OPTN) can cause ALS. Therefore, we sequenced OPTN in 371 FTLD cases but no mutations were detected, suggesting changes in OPTN do not cause FTLD.

P2-106: UBAP1 is a risk factor for frontotemporal lobar degeneration

located in the right parietal lobe (Figure 1) was observed while the score of MMSE remained unchanged. There were no areas of significantly decreased FA, increase MD or decreased MD observed in AD patients compared with controls. Conclusions: Our preliminary result showed changes of brain diffusivity can be detected prior to the significant change of clinical manifestations. In agreement with previous studies, we found the involvement of white matter in parietal lobe which may be one the first brain regions in response to the treatment. We conclude that Donepezil treatment bring new changes in brain structures of AD patients, and DTI (especially FA) may be used to monitor the early therapeutic effect.