The fused in sarcoma (FUS) protein has been shown to be a significant disease protein in a subgroup of patients with frontotemporal lobar degeneration (FTLD). Nevertheless, the mechanism underlying FUS associated FTLD is only poorly understood. Recent research has identified a large hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9orf72), reinforcing the association between C9orf72 and FTLD. Moreover, an unusual histopathological change has been observed within the granule cell layer of the cerebellum in chromosome 9p-linked frontotemporal dementia with motor neuron disease. Whether this type of cerebellar pathology is a pathological marker for chromosome 9p-linked families remains unknown. The purpose of this study was to genetically, neuropathologically and biochemically characterize FUS and C9orf72 in FTLD, and also to investigate the association between the cerebellar pathology and chromosome 9p-linked families. The genetic sequencing study searching for potential genetic factors of FUS in FTLD failed to detect any pathogenic mutations or variations. Immunohistochemical study for FUS pathology in FTLD provided strong evidence for FUS being the specific pathological protein in all forms of FTLD-FUS. Immunoblotting for FUS in FTLD detected one novel disease-associated FUS aggregate (~37 kDa) in the urea fraction of atypical FTLD with ubiquitinated inclusions (aFTLD-U) frontal cortical samples, suggesting this unique protein product might be more associated with disease than the full-length protein itself. Immunohistochemical study of C9orf72 in FTLD detected a 'synaptic' staining in CA sectors, as the most prominent histological feature identified. Immunoblotting for C9orf72 protein demonstrated no distinctive bands among different diagnostic groups, in frontal and cerebellar cortical regions. The present study also confirmed the presence of cerebellar p62 neuronal cytoplasmic inclusions (NCI) in a proportion of FTLD-TDP cases. Although most of these cases showed an autosomally dominant pattern of inheritance, not all of them shared a common C9orf72 haplotype, or mutation in C9orf72.Much work is still needed to investigate the underlying pathogenesis of FTLD-FUS. Attention should still be given to identifying possible genetic risk factors in FUS using a large series of FTLD samples and searching for other possible proteins within the FUS immunoreactive neuronal inclusions. Moreover, the target protein within the cerebellar p62 NCI remains unknown, but it is clear that it is not C9orf72 protein.
|Date of Award||1 Aug 2012|
- The University of Manchester
|Supervisor||David Mann (Supervisor) & Stuart Pickering-Brown (Supervisor)|