Characterization of TDP-43 changes during normal aging: a postmortem study

Abstract

The elderly population is growing worldwide, especially in developing countries. It is happening due to the progressive decline of fertility and mortality and the improvement in quality of life of these populations. Among the aging related diseases, neurodegenerative diseases are one of the most prevalent and disabling. Neurodegenerative diseases have several common features, including the accumulation of abnormal specific proteins in the brain. In 2006, a DNA-binding protein that has 43-kDa (TDP-43) was identified as the major abnormal protein in cases of Frontotemporal Lobar Degeneration (FTLD). Association of TDP-43 with FTLDs was a surprising finding and little was known about its action mechanism, function or behavior in normal aging. Despite the advances in TDP-43 studies, normative basis are still lacking. The threshold between its physiological and pathological role is still unknown. Normative controls although necessary are difficult to produce due to the increasing drop of autopsy rates worldwide. For this reason, the collection of the Brain Bank of the Brazilian Aging Brain Study Group (BBBABSG) on University of Sao Paulo Medical School (MSUSP) is a window of opportunity for generating such important basis. The BBBABSG comprise a large number of well-characterized brains of elderly non-demented subjects, which enables us to further study the non-pathological aging human brain. We propose to analyze systematically the distribution of phosphorylated (abnormal) TDP-43 protein in normal human aging in a large archived sample of 400 subjects. Subjects were previously classified clinically and anatopatologically as normal controls and subjected to the exact same protocol. Selected areas will be immunostained against phosphorylated TDP-43 protein. We will analyze frequently vulnerable areas to FTLD-TDP-43. TDP-43 inclusions will be evaluated by semi-quantitative methods, per area. These analyzes will be conducted according to stereological principles with the use of Image J software. Areas of interest will be compared using linear statistics models. Our proposal is to reveal whether the TDP-43 modifications are necessarily synonymous of disease and whether there are preferred vulnerability areas to initial developmental of disease, or not. Although apparently this study is essentially descriptive, similar approaches resulted in understanding of early stages of neurodegenerative diseases, such as Alzheimer's disease. We will also characterize TDP-43 inclusions by biochemical essays. In these experiments we will verify whether TDP-43 modifications have a similar biochemical pattern that has been seen in cases of FTLD-TDP. For this study we will carry out immunoblotting. We will use FTLD cases (n=10) in both experiments. We believe that this study can accelerate our understanding of TDP-43 changes during ages and assist us in determining targets for early stage interventions. (AU)