Frontotemporal dementia and parkinsonism associated with the IVS1+1G→A mutation in progranulin: A clinicopathologic study

Department of Neurology, Mayo Clinic Rochester, MN 55905, USA.
Brain (Impact Factor: 9.2). 12/2006; 129(Pt 11):3103-14. DOI: 10.1093/brain/awl268
Source: PubMed


We previously reported a kindred with three cases of dementia, in which the proband exhibited features typical of frontotemporal dementia and parkinsonism (FTDP). An arginine insertion at codon 352 (insR352) in the presenilin-1 (PSEN1) gene was identified in the proband, but analyses in plasma and CSF suggested a mechanism of neurodegeneration not directly related to amyloid pathophysiology. The proband was followed with yearly evaluations of functional, clinical, neuropsychologic, neuropsychiatric and radiologic status, which showed relatively linear change over the initial 4 years of assessment. Upon the proband's death at age 63, neuropathologic examination revealed frontotemporal lobar degeneration (FTLD) with ubiquitin-positive inclusions (FTLD-U). We recently identified several kindreds with familial FTDP associated with mutations in the progranulin (PGRN) gene, particularly in those cases with neuronal intranuclear inclusions. Our proband was indeed found to have such inclusions, and PGRN analysis in this proband revealed the G to A mutation in the exon 1 splice donor site (IVS1+1G-->A) which is predicted to destroy the 5'-splice site of exon 1 and remove the start methionine codon and hence completely block any PGRN protein from being generated. These findings suggest that the insR352 PSEN1 is not pathogenic, and the IVS1+1G-->A mutation in PGRN causes FTDP associated with FTLD-U pathology and represents a new class of neurodegenerative disease--the 'hypoprogranulinopathies'.

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    • "Parkinsonism in FTLD is generally poorly or not responsive to Levodopa [11] [16], similarly to most cases of atypical parkinsonism, although different degrees of clinical improvement after Levodopa administration have been reported [5] [13]. In our case, extrapyramidal signs did not improve with Levodopa, although we cannot exclude that quetiapine partially reduced its effect being a dopamine-receptor blocking agent. "
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    ABSTRACT: Parkinsonism can be the presenting feature of frontotemporal dementia due to Progranulin (GRN) mutations or develop over the course of the disease, mimicking idiopathic Parkinson's disease or atypical parkinsonism. Here we report on a patient carrying a novel GRN mutation who presented with asymmetric parkinsonism and developed cognitive decline and language alterations two years later. Brain MRI showed mild asymmetric fronto-parietal atrophy. Single-photon emission computed tomography with I123 ioflupane (DAT-Scan) demonstrated reduced tracer uptake in the left putamen. Larger studies are needed to clarify whether presynaptic dopaminergic deficit is present in all GRN mutation carriers or only in those with parkinsonism.
    Full-text · Article · Sep 2013 · Journal of Alzheimer's disease: JAD
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    • "Mutations in a second gene in chromosome 17, named progranulin (GRN), were discovered in 2006 [32, 33]. GRN mutations cause about 5–10% of all FTLD cases, varying depending on the population considered (see [17] for review). "
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    ABSTRACT: In the last few years, genetic and biomolecular mechanisms at the basis of Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) have been unraveled. A key role is played by microglia, which represent the immune effector cells in the central nervous system (CNS). They are extremely sensitive to the environmental changes in the brain and are activated in response to several pathologic events within the CNS, including altered neuronal function, infection, injury, and inflammation. While short-term microglial activity has generally a neuroprotective role, chronic activation has been implicated in the pathogenesis of neurodegenerative disorders, including AD and FTLD. In this framework, the purpose of this review is to give an overview of clinical features, genetics, and novel discoveries on biomolecular pathogenic mechanisms at the basis of these two neurodegenerative diseases and to outline current evidence regarding the role played by activated microglia in their pathogenesis.
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    • "This hypothesis finds support in (a) experimental results with Psen knockout mice (Saura et al, 2004), where progressive neurodegeneration occurs without Ab deposition, and (b) in three case reports in which missense mutations in PSEN genes displayed neurodegenerative clinical phenotypes but no Ab accumulation (discussed in Shen and Kelleher, 2007; Kelleher and Shen, 2010). However, this last argument has been considerably weakened by follow-up studies showing that neurodegeneration was likely caused by a second mutation in the progranulin gene in one case (Boeve et al, 2006), whereas in a second case abundant amyloid deposition in the frontal lobe appeared at autopsy (for further discussion, see Bergmans and De Strooper, 2010). On the other hand, recent observations in patients suffering from familial acne inversa in China (Wang et al, 2010) and independently in Great Britain (Pink et al, 2011) raise doubts about the validity of the 'simple' g-secretase loss-of-function hypothesis. "
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    ABSTRACT: The mechanisms by which mutations in the presenilins (PSEN) or the amyloid precursor protein (APP) genes cause familial Alzheimer disease (FAD) are controversial. FAD mutations increase the release of amyloid β (Aβ)42 relative to Aβ40 by an unknown, possibly gain-of-toxic-function, mechanism. However, many PSEN mutations paradoxically impair γ-secretase and 'loss-of-function' mechanisms have also been postulated. Here, we use kinetic studies to demonstrate that FAD mutations affect Aβ generation via three different mechanisms, resulting in qualitative changes in the Aβ profiles, which are not limited to Aβ42. Loss of ɛ-cleavage function is not generally observed among FAD mutants. On the other hand, γ-secretase inhibitors used in the clinic appear to block the initial ɛ-cleavage step, but unexpectedly affect more selectively Notch than APP processing, while modulators act as activators of the carboxypeptidase-like (γ) activity. Overall, we provide a coherent explanation for the effect of different FAD mutations, demonstrating the importance of qualitative rather than quantitative changes in the Aβ products, and suggest fundamental improvements for current drug development efforts.
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