- Email: [email protected]
P2-181: Amino acid sequence of BACE1 and BACE2 determine different subcellular transport and localisation
Poster Presentations P2: understand disease progression in the hippocampus--a region critical for memory formation--in PrP-MAPT mice that over-express normal human fetal tau (3R/0N isoform). Methods: Field potential recordings were made from the lateral perforant path of the dentate gyrus of either wild-type or heterozygous mice aged 2 and 4 months, respectively, and include assessments of basal transmission, paired-pulse facilitation (PPF) and long-term potentiation (LTP). Results: At 2 months, no difference in the magnitude of LTP between genotypes was observed (Het: 176.4 ⫾ 10.2%, n ⫽ 6; WT: 171.3 ⫾ 9.1, n ⫽ 6) but a subtle impairment in basal transmission was detected in the Het’s even at this early age. By 4 months of age, differences in basal transmission, PPF, and LTP (WT: 178.2 ⫾ 6.4, n ⫽ 6; Het: 148.1 ⫾ 11.9, n ⫽ 9) were observed. Interestingly, 4M Het LTP data revealed that some slices had normal, WT LTP magnitudes while others were impaired. This duality suggests that at 4 months, Het mice may reside on a threshold between normal and abnormal and that other factors influence the progression of symptoms. Further studies will include assessments in 8-10M old Tau transgenic mice. Conclusions: These data suggest that overexpression of normal tau protein influences hippocampal synaptic properties, similar to deficits found in Tg2576 mice, early in development and thus may be important in the disease progression. P2-179
SMALL-MOLECULE PROBES OF TAU FIBRILLIZATION
Nicolette S. Honson, Bhaswati Bhandyopadhyay, Edward Chang, Swati B. Naphade, Jordan R. Jensen, Jeff Kuret, The Ohio State University, Columbus, OH, USA. Contact e-mail: [email protected] Background: Alzheimer’s disease (AD) is characterized in part by misfolding of monomeric tau protein to form neurofibrillary lesions. Because they are established markers and potential mediators of neurodegeneration, neurofibrillary lesions are targets for development of small molecules with diagnostic and therapeutic potential. Objectives: To characterize the interaction of small molecules with tau monomers and filaments. Methods: Small molecules that interact with tau protein were identified through high throughput screening methods in collaboration with the Molecular Library Screening Center Network. The activity of individual molecules was then assessed using in vitro and cellular tau aggregation assays. Results: Compounds were identified that interacted with tau in three distinct modalities. First, in the high concentration regime (10 micromolar), compounds such as Congo red acted as fibrillization agonists when assayed under physiological buffer conditions and tau concentrations. Agonist-mediated aggregation followed a classic homogeneous nucleation scheme characterized by a dimeric nucleus and extension through monomer addition. Members of this group that were capable of crossing cell membranes also induced tau aggregation in HEK293 cells and primary neurons. Second, in the low concentration regime (⬍1 micromolar), certain compounds were capable of binding tau filaments with submicromolar affinity and 10-fold selectivity relative to alpha-synuclein or beta-amyloid aggregates. Finally, the low concentration regime also identified compounds that were capable of antagonizing poly-anion induced tau fibrillization. A structure-activity relationship for one antagonist family composed of cyanine derivatives showed that inhibitory activity was a function of molecular length and charge. Conclusions: Tau is a rich target for small molecule development. First, small molecules can overcome the bottlenecks in tau aggregation, and therefore facilitate modeling of the aggregation reaction in vitro and in cells. These agents offer a novel approach for assessing toxicity associated with tau aggregates. Second, small molecules are capable of binding tau aggregates selectively relative to aggregates composed of beta-amyloid and alpha-synuclein. These agents may have utility as imaging agents for pre-mortem diagnosis and staging of tauopathies. Finally, it is possible to modulate the aggregation reaction using fibrillization antagonists such as cyanine dyes. This approach may have potential for blocking lesion formation in disease.
P2-180
T423 HIGH-MOLECULAR–WEIGHT MACROMOLECULAR INHIBITOR IN HUMAN AND ANIMAL BRAIN EXTRACTS POTENTLY INHIBITS CHAPERONE-CATALYZED REACTIVATION OF HEAT DENATURED LUCIFERASE
Harry LeVine, III, University of Kentucky, Lexington, KY, USA. Contact e-mail: [email protected] Background: In spite of a complement of cellular chaperones, misfolded proteins accumulate with aging in some individuals. The brain is particularly prone to this build up, resulting in a number of chronic neurodegenerative diseases including Alzheimer’s disease. Decreased chaperone levels with aging and the inability of some neurons to upregulate their cytosolic chaperone system in response to stress are suggested to contribute to neuronal dysfunction and cell death. What is missing is the measurement of chaperone function in control and AD brain tissue. Methods: While cytosolic chaperone activity can be followed in transfected cultured cells, measurements in post-mortem human brain extracts have not been reported. We find that human and rat brain contain a soluble high-molecular weight factor that inhibits heat-denatured firefly luciferase reactivation in the chaperone refolding rabbit reticulocyte lysate (RRL) model system. Results: The inhibitory activity is highest in extracts of rat brain and lowest in cardiac and skeletal muscle, and is interacting with components in the RRL rather than the denatured luciferase. The inhibitory activity is heat-sensitive and has been purified through ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. It co-migrates with a multi-protein complex but not with BAG-1 although recombinant BAG-1 inhibits luciferase reactivation in the RRL system with an IC50 ⬃ 100 nM. Conclusions: The proteins in the inhibitory complex are being identified by mass spectroscopy of their tryptic fragments for immunodepletion and supplementation experiments to determine the molecular basis of the inhibition. P2-181
AMINO ACID SEQUENCE OF BACE1 AND BACE2 DETERMINE DIFFERENT SUBCELLULAR TRANSPORT AND LOCALISATION
Patrick Wunderlich1, Tina Wahle2, Jochen Walter1, 1Department of Neurology, University of Bonn, Bonn, Germany; 2Department of Human Genetics, K. U. Leuven, Leuven, Belgium. Contact e-mail: [email protected] Background: The amyloid- protein (A) accumulates in senile plaques in the brains of Alzheimer Disease patients and is generated by sequential cleavage of the amyloid precursor protein (APP) by -secretase (BACE1) and ␥-secretase. BACE1 cleaves APP at the -site within endosomal and lysosomal compartments to generate a membrane-bound C-terminal fragment (CTF) which can be further processed by ␥-secretase to release A. Transport of BACE1 to these compartments is mediated by binding to the monomeric adaptor protein, ␥-ear containing, ADP-ribosylation factor binding protein 1 (GGA1). An acidic DXXLL motif in the C-terminus of BACE1 is critical for interaction with GGA protein. The interaction of BACE1 and GGA1 is regulated by phosphorylation of a serine residue inside the binding motif (Wahle et al., 2005). BACE2 a homologue of BACE1, is mainly expressed in glia cells in the brain and cleaves APP more like ␣-secretase in the A-domain thereby decreasing the generation of A. Although BACE2 shares more than 50 % sequence homology with BACE1, it has striking differences regarding stability and intracellular transport (Fluhrer et al., 2002). Since BACE2 does not contain a canonical DXXLL motif, it does not bind to GGA1 and shows a predominant localisation in the Golgi. Methods: The mutation of two amino acids in the C-terminus of BACE2 results in a GGA1 binding motif. To modulate interaction of BACE2 with GGAs, we generated GFP-tagged and mCherry-tagged variants of the BACE2 C-terminus, with only one or both amino acids mutated. To study the subcellular localisation, these mutants were then used for fluorescence microscopy. Results: The performed
T424
Poster Presentations P2:
fluorescence microscopy revealed that a BACE2 variant with a full DXXLL motif has a broader distribution in the cell as compared to the wildtype variant. This finding was supported by using additional BACE2 mutants and co-localisation studies with BACE1. Conclusions: Together, our findings indicate that the amino acid sequence of the cytoplasmic domain determines the distinct subcellular localisation and transport of BACE1 and BACE2. P2-182
GELASTIC DEMENTIA: LAUGHTER REPLACING SPEECH IN FRONTOTEMPORAL LOBAR DEGENERATION
Jonathan D. Rohrer, Jason D. Warren, Martin N. Rossor, Institute of Neurology, London, United Kingdom. Contact e-mail: [email protected] Background: Relatively early and selective breakdown of speech output is a feature of the frontotemporal lobar degenerations (FTLD), a clinically, radiologically and pathologically diverse group of diseases characterised by progressive focal atrophy of the frontal and temporal lobes. Methods: We describe ten patients with a clinical diagnosis of FTLD (pathologically confirmed in three cases) who developed abnormal laughter in the context of progressive speech production impairment leading to mutism. Results: Failure of speech output was accompanied by increasing frequency of laughter until ultimately the only extended utterance was laughter. Laughter did not show contextual sensitivity but occurred as an automatic vocal output that replaced speech. Acoustic analysis of the laughter in two patients revealed abnormal motor features including variable note duration and inter-note interval, loss of temporal symmetry of laugh notes and loss of the normal decrescendo. We propose the term ‘gelastic dementia’ for this syndrome of abnormal laughter in FTLD. Voxel-based morphometric analysis of brain MRI in patients with gelastic dementia compared to a closely matched disease-control group without abnormal laughter revealed decreased grey matter in the right parahippocampal gyrus and temporal pole in the gelastic group and decreased grey matter in the right superior temporal gyrus in the disease-control group. Conclusions: Gelastic dementia may be a hallmark of a subgroup in the FTLD spectrum with impaired control and production of nonverbal vocal behaviour due to disruption of fronto-temporal networks mediating vocalisation. P2-183
GENERALISED BRAIN ATROPHY PREDATES SYMPTOM ONSET IN FRONTOTEMPORAL DEMENTIA CAUSED BY CHMP2B MUTATION
Laila Ahsan1, Jonathan D. Rohrer1, Adrian Isaacs1, Jorgen E. Nielsen2,3, Leif Ostergaard4, Rachael Scahill1, Martin N. Rossor1, Jason D. Warren1, Nick C. Fox1, Peter Johannsen2, FReJA Consortium, 1Institute of Neurology, UCL, London, United Kingdom; 2Copenhagen University Hospital, Copenhagen, Denmark; 3 University of Copenhagen, Copenhagen, Denmark; 4Aarhus University Hospital, Aarhus, Denmark. Contact e-mail: [email protected] Background: Mutations in CHMP2B located on chromosome 3 are a rare cause of familial frontotemporal dementia (FTD). Clinically, behavioural and personality changes are typically prominent, though deficits in language, memory, calculation and praxis have also been noted in the early stages. To date, detailed brain imaging studies of CHMP2B subjects have not been conducted. Methods: Sixteen members of the Danish family with CHMP2B mutation-associated frontotemporal dementia (FTD-3) (9 presymptomatic mutation carriers (PMC), 7 non-carrier controls) underwent serial volumetric brain MRI scans with a mean interval of 16 months. Scans from 19 pathologically confirmed tau-positive frontotemporal lobar degeneration (FTLD) subjects were used for comparing regional patterns of atrophy. Results: Compared with healthy controls, the PMC group had significantly higher mean rates of whole brain atrophy (1.34% per year versus -0.10% per year, p⫽0.009) and ventricular enlargement (p⫽0.04). Rates of atrophy for each hemisphere were increased relative to controls (p⬍0.05 for both hemispheres), but there was no evidence for left-right
asymmetry of atrophy in the PMC group, nor for an increased ratio of atrophy in the anterior compared with the posterior brain. In contrast, the tau-positive FTLD group had a significantly higher ratio of anterior to posterior cerebral atrophy than the PMC group. Conclusions: Our findings suggest that generalised brain atrophy occurs at the preclinical stage of CHMP2B mutation-associated FTD. This is in contrast to other disorders in the FTLD spectrum in which early regional atrophy of the frontal and temporal lobes occurs. This early generalized atrophy, combined with the recent finding that the ubiquitin-positive, tau-negative inclusions in CHMP2B do not contain the protein TDP-43, underline a pathogenetic distinction between CHMP2B mutation-associated FTD and the other genetic and sporadic forms of FTLD. Further work is needed to elucidate why CHMP2B mutations present with a clinical FTD syndrome with primarily behavioural changes consistent with other FTLD syndromes despite the early generalized cortical damage. P2-184
IDENTIFICATION OF A NOVEL CHROMOSOMAL LOCUS IN A BELGIAN FTLD-MND FAMILY
Ilse Gijselinck, Julie van der Zee, Ivy Cuijt, Githa Maes, Karin Peeters, Christine Van Broeckhoven, Marc Cruts, Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB; Laboratory of Neurogenetics, Institute Born-Bunge; and University of Antwerp, Antwerpen, Belgium. Contact e-mail: [email protected] Background: Frontotemporal lobar degeneration (FTLD) is a neurodegenerative brain disorder with a prevalence similar to that of Alzheimer’s disease in the population below age 65 years. In some patients FTLD symptoms are accompanied by signs of motor neuron disease (MND). A positive family history is observed in up to 50% of FTLD patients indicating a significant contribution of genetics to the etiology of FTLD. A high degree of genetic heterogeneity has been observed with different mutations in the genes encoding the microtubule-associated protein (MAPT), progranulin (PGRN), charged multivesicular body protein 2B (CHMP2B) and valosin containing protein (VCP). Further, two loci on chromosome 9 at 9q21-q22 and 9p13-21 were implicated in FTLD with MND (FTLD-MND). Methods: In Belgian familial FTLD patients 65% remained unexplained by mutations in known FTLD genes. Of one patient diagnosed with FTLD-MND, we collected DNA of relatives and performed a genome-wide scan. Results: We identified and finemapped a novel chromosomal locus that was not previously linked to FTLD and/or MND. Haplotype analysis identified a risk haplotype of 23 cM that co-segregated with disease. Further reduction of the candidate region and mutation analyses of positional and functional candidate genes are ongoing. Conclusions: Identification of the mutation in the underlying disease gene will significantly contribute to the understanding of neurodegenerative disease mechanisms in FTLD. P2-185
FTLD-U–LINKED MISSENSE MUTATIONS IN VCP/P97 ALTER LOCALIZATION OF ENDOGENOUS TDP-43 AND INDUCE CELL DEATH
Michael A. Gitcho1, Jeffrey Strider1, Deborah Carter1, Lisa Taylor-Reinwald1, Mark S. Forman2, John C. Morris1, Alison M. Goate1, Nigel J. Cairns1, 1Washington University School of Medicine, St. Louis, MO, USA; 2University of Pennsylvania School of Medicine, Philadelphia, PA, USA. Contact e-mail: [email protected] Background: Frontotemporal dementia with inclusion body myopathy and Paget disease of bone (IBMPFD) is a rare, autosomal-dominant disorder caused by mutations in the valosin-containing protein (VCP) gene. The disease is characterized neuropathologically by frontal and temporal lobar atrophy, neuron loss and gliosis, and a pattern of ubiquitin-positive inclusions (FTLD-U) which is distinct from that seen in other sporadic and familial FTLD-U entities. The major component of the ubiquitinated inclusions of FTLD with VCP mutation is the TAR DNA-binding protein 43
SMALL-MOLECULE PROBES OF TAU FIBRILLIZATION
Nicolette S. Honson, Bhaswati Bhandyopadhyay, Edward Chang, Swati B. Naphade, Jordan R. Jensen, Jeff Kuret, The Ohio State University, Columbus, OH, USA. Contact e-mail: [email protected] Background: Alzheimer’s disease (AD) is characterized in part by misfolding of monomeric tau protein to form neurofibrillary lesions. Because they are established markers and potential mediators of neurodegeneration, neurofibrillary lesions are targets for development of small molecules with diagnostic and therapeutic potential. Objectives: To characterize the interaction of small molecules with tau monomers and filaments. Methods: Small molecules that interact with tau protein were identified through high throughput screening methods in collaboration with the Molecular Library Screening Center Network. The activity of individual molecules was then assessed using in vitro and cellular tau aggregation assays. Results: Compounds were identified that interacted with tau in three distinct modalities. First, in the high concentration regime (10 micromolar), compounds such as Congo red acted as fibrillization agonists when assayed under physiological buffer conditions and tau concentrations. Agonist-mediated aggregation followed a classic homogeneous nucleation scheme characterized by a dimeric nucleus and extension through monomer addition. Members of this group that were capable of crossing cell membranes also induced tau aggregation in HEK293 cells and primary neurons. Second, in the low concentration regime (⬍1 micromolar), certain compounds were capable of binding tau filaments with submicromolar affinity and 10-fold selectivity relative to alpha-synuclein or beta-amyloid aggregates. Finally, the low concentration regime also identified compounds that were capable of antagonizing poly-anion induced tau fibrillization. A structure-activity relationship for one antagonist family composed of cyanine derivatives showed that inhibitory activity was a function of molecular length and charge. Conclusions: Tau is a rich target for small molecule development. First, small molecules can overcome the bottlenecks in tau aggregation, and therefore facilitate modeling of the aggregation reaction in vitro and in cells. These agents offer a novel approach for assessing toxicity associated with tau aggregates. Second, small molecules are capable of binding tau aggregates selectively relative to aggregates composed of beta-amyloid and alpha-synuclein. These agents may have utility as imaging agents for pre-mortem diagnosis and staging of tauopathies. Finally, it is possible to modulate the aggregation reaction using fibrillization antagonists such as cyanine dyes. This approach may have potential for blocking lesion formation in disease.
P2-180
T423 HIGH-MOLECULAR–WEIGHT MACROMOLECULAR INHIBITOR IN HUMAN AND ANIMAL BRAIN EXTRACTS POTENTLY INHIBITS CHAPERONE-CATALYZED REACTIVATION OF HEAT DENATURED LUCIFERASE
Harry LeVine, III, University of Kentucky, Lexington, KY, USA. Contact e-mail: [email protected] Background: In spite of a complement of cellular chaperones, misfolded proteins accumulate with aging in some individuals. The brain is particularly prone to this build up, resulting in a number of chronic neurodegenerative diseases including Alzheimer’s disease. Decreased chaperone levels with aging and the inability of some neurons to upregulate their cytosolic chaperone system in response to stress are suggested to contribute to neuronal dysfunction and cell death. What is missing is the measurement of chaperone function in control and AD brain tissue. Methods: While cytosolic chaperone activity can be followed in transfected cultured cells, measurements in post-mortem human brain extracts have not been reported. We find that human and rat brain contain a soluble high-molecular weight factor that inhibits heat-denatured firefly luciferase reactivation in the chaperone refolding rabbit reticulocyte lysate (RRL) model system. Results: The inhibitory activity is highest in extracts of rat brain and lowest in cardiac and skeletal muscle, and is interacting with components in the RRL rather than the denatured luciferase. The inhibitory activity is heat-sensitive and has been purified through ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. It co-migrates with a multi-protein complex but not with BAG-1 although recombinant BAG-1 inhibits luciferase reactivation in the RRL system with an IC50 ⬃ 100 nM. Conclusions: The proteins in the inhibitory complex are being identified by mass spectroscopy of their tryptic fragments for immunodepletion and supplementation experiments to determine the molecular basis of the inhibition. P2-181
AMINO ACID SEQUENCE OF BACE1 AND BACE2 DETERMINE DIFFERENT SUBCELLULAR TRANSPORT AND LOCALISATION
Patrick Wunderlich1, Tina Wahle2, Jochen Walter1, 1Department of Neurology, University of Bonn, Bonn, Germany; 2Department of Human Genetics, K. U. Leuven, Leuven, Belgium. Contact e-mail: [email protected] Background: The amyloid- protein (A) accumulates in senile plaques in the brains of Alzheimer Disease patients and is generated by sequential cleavage of the amyloid precursor protein (APP) by -secretase (BACE1) and ␥-secretase. BACE1 cleaves APP at the -site within endosomal and lysosomal compartments to generate a membrane-bound C-terminal fragment (CTF) which can be further processed by ␥-secretase to release A. Transport of BACE1 to these compartments is mediated by binding to the monomeric adaptor protein, ␥-ear containing, ADP-ribosylation factor binding protein 1 (GGA1). An acidic DXXLL motif in the C-terminus of BACE1 is critical for interaction with GGA protein. The interaction of BACE1 and GGA1 is regulated by phosphorylation of a serine residue inside the binding motif (Wahle et al., 2005). BACE2 a homologue of BACE1, is mainly expressed in glia cells in the brain and cleaves APP more like ␣-secretase in the A-domain thereby decreasing the generation of A. Although BACE2 shares more than 50 % sequence homology with BACE1, it has striking differences regarding stability and intracellular transport (Fluhrer et al., 2002). Since BACE2 does not contain a canonical DXXLL motif, it does not bind to GGA1 and shows a predominant localisation in the Golgi. Methods: The mutation of two amino acids in the C-terminus of BACE2 results in a GGA1 binding motif. To modulate interaction of BACE2 with GGAs, we generated GFP-tagged and mCherry-tagged variants of the BACE2 C-terminus, with only one or both amino acids mutated. To study the subcellular localisation, these mutants were then used for fluorescence microscopy. Results: The performed
T424
Poster Presentations P2:
fluorescence microscopy revealed that a BACE2 variant with a full DXXLL motif has a broader distribution in the cell as compared to the wildtype variant. This finding was supported by using additional BACE2 mutants and co-localisation studies with BACE1. Conclusions: Together, our findings indicate that the amino acid sequence of the cytoplasmic domain determines the distinct subcellular localisation and transport of BACE1 and BACE2. P2-182
GELASTIC DEMENTIA: LAUGHTER REPLACING SPEECH IN FRONTOTEMPORAL LOBAR DEGENERATION
Jonathan D. Rohrer, Jason D. Warren, Martin N. Rossor, Institute of Neurology, London, United Kingdom. Contact e-mail: [email protected] Background: Relatively early and selective breakdown of speech output is a feature of the frontotemporal lobar degenerations (FTLD), a clinically, radiologically and pathologically diverse group of diseases characterised by progressive focal atrophy of the frontal and temporal lobes. Methods: We describe ten patients with a clinical diagnosis of FTLD (pathologically confirmed in three cases) who developed abnormal laughter in the context of progressive speech production impairment leading to mutism. Results: Failure of speech output was accompanied by increasing frequency of laughter until ultimately the only extended utterance was laughter. Laughter did not show contextual sensitivity but occurred as an automatic vocal output that replaced speech. Acoustic analysis of the laughter in two patients revealed abnormal motor features including variable note duration and inter-note interval, loss of temporal symmetry of laugh notes and loss of the normal decrescendo. We propose the term ‘gelastic dementia’ for this syndrome of abnormal laughter in FTLD. Voxel-based morphometric analysis of brain MRI in patients with gelastic dementia compared to a closely matched disease-control group without abnormal laughter revealed decreased grey matter in the right parahippocampal gyrus and temporal pole in the gelastic group and decreased grey matter in the right superior temporal gyrus in the disease-control group. Conclusions: Gelastic dementia may be a hallmark of a subgroup in the FTLD spectrum with impaired control and production of nonverbal vocal behaviour due to disruption of fronto-temporal networks mediating vocalisation. P2-183
GENERALISED BRAIN ATROPHY PREDATES SYMPTOM ONSET IN FRONTOTEMPORAL DEMENTIA CAUSED BY CHMP2B MUTATION
Laila Ahsan1, Jonathan D. Rohrer1, Adrian Isaacs1, Jorgen E. Nielsen2,3, Leif Ostergaard4, Rachael Scahill1, Martin N. Rossor1, Jason D. Warren1, Nick C. Fox1, Peter Johannsen2, FReJA Consortium, 1Institute of Neurology, UCL, London, United Kingdom; 2Copenhagen University Hospital, Copenhagen, Denmark; 3 University of Copenhagen, Copenhagen, Denmark; 4Aarhus University Hospital, Aarhus, Denmark. Contact e-mail: [email protected] Background: Mutations in CHMP2B located on chromosome 3 are a rare cause of familial frontotemporal dementia (FTD). Clinically, behavioural and personality changes are typically prominent, though deficits in language, memory, calculation and praxis have also been noted in the early stages. To date, detailed brain imaging studies of CHMP2B subjects have not been conducted. Methods: Sixteen members of the Danish family with CHMP2B mutation-associated frontotemporal dementia (FTD-3) (9 presymptomatic mutation carriers (PMC), 7 non-carrier controls) underwent serial volumetric brain MRI scans with a mean interval of 16 months. Scans from 19 pathologically confirmed tau-positive frontotemporal lobar degeneration (FTLD) subjects were used for comparing regional patterns of atrophy. Results: Compared with healthy controls, the PMC group had significantly higher mean rates of whole brain atrophy (1.34% per year versus -0.10% per year, p⫽0.009) and ventricular enlargement (p⫽0.04). Rates of atrophy for each hemisphere were increased relative to controls (p⬍0.05 for both hemispheres), but there was no evidence for left-right
asymmetry of atrophy in the PMC group, nor for an increased ratio of atrophy in the anterior compared with the posterior brain. In contrast, the tau-positive FTLD group had a significantly higher ratio of anterior to posterior cerebral atrophy than the PMC group. Conclusions: Our findings suggest that generalised brain atrophy occurs at the preclinical stage of CHMP2B mutation-associated FTD. This is in contrast to other disorders in the FTLD spectrum in which early regional atrophy of the frontal and temporal lobes occurs. This early generalized atrophy, combined with the recent finding that the ubiquitin-positive, tau-negative inclusions in CHMP2B do not contain the protein TDP-43, underline a pathogenetic distinction between CHMP2B mutation-associated FTD and the other genetic and sporadic forms of FTLD. Further work is needed to elucidate why CHMP2B mutations present with a clinical FTD syndrome with primarily behavioural changes consistent with other FTLD syndromes despite the early generalized cortical damage. P2-184
IDENTIFICATION OF A NOVEL CHROMOSOMAL LOCUS IN A BELGIAN FTLD-MND FAMILY
Ilse Gijselinck, Julie van der Zee, Ivy Cuijt, Githa Maes, Karin Peeters, Christine Van Broeckhoven, Marc Cruts, Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB; Laboratory of Neurogenetics, Institute Born-Bunge; and University of Antwerp, Antwerpen, Belgium. Contact e-mail: [email protected] Background: Frontotemporal lobar degeneration (FTLD) is a neurodegenerative brain disorder with a prevalence similar to that of Alzheimer’s disease in the population below age 65 years. In some patients FTLD symptoms are accompanied by signs of motor neuron disease (MND). A positive family history is observed in up to 50% of FTLD patients indicating a significant contribution of genetics to the etiology of FTLD. A high degree of genetic heterogeneity has been observed with different mutations in the genes encoding the microtubule-associated protein (MAPT), progranulin (PGRN), charged multivesicular body protein 2B (CHMP2B) and valosin containing protein (VCP). Further, two loci on chromosome 9 at 9q21-q22 and 9p13-21 were implicated in FTLD with MND (FTLD-MND). Methods: In Belgian familial FTLD patients 65% remained unexplained by mutations in known FTLD genes. Of one patient diagnosed with FTLD-MND, we collected DNA of relatives and performed a genome-wide scan. Results: We identified and finemapped a novel chromosomal locus that was not previously linked to FTLD and/or MND. Haplotype analysis identified a risk haplotype of 23 cM that co-segregated with disease. Further reduction of the candidate region and mutation analyses of positional and functional candidate genes are ongoing. Conclusions: Identification of the mutation in the underlying disease gene will significantly contribute to the understanding of neurodegenerative disease mechanisms in FTLD. P2-185
FTLD-U–LINKED MISSENSE MUTATIONS IN VCP/P97 ALTER LOCALIZATION OF ENDOGENOUS TDP-43 AND INDUCE CELL DEATH
Michael A. Gitcho1, Jeffrey Strider1, Deborah Carter1, Lisa Taylor-Reinwald1, Mark S. Forman2, John C. Morris1, Alison M. Goate1, Nigel J. Cairns1, 1Washington University School of Medicine, St. Louis, MO, USA; 2University of Pennsylvania School of Medicine, Philadelphia, PA, USA. Contact e-mail: [email protected] Background: Frontotemporal dementia with inclusion body myopathy and Paget disease of bone (IBMPFD) is a rare, autosomal-dominant disorder caused by mutations in the valosin-containing protein (VCP) gene. The disease is characterized neuropathologically by frontal and temporal lobar atrophy, neuron loss and gliosis, and a pattern of ubiquitin-positive inclusions (FTLD-U) which is distinct from that seen in other sporadic and familial FTLD-U entities. The major component of the ubiquitinated inclusions of FTLD with VCP mutation is the TAR DNA-binding protein 43