Cytoplasmic TDP‐43 accumulation in cells of the adrenal medulla in individuals with or without amyotrophic lateral sclerosis

The transactive response DNA ‐binding protein of 43 kDa ( TDP ‐43) is normally located predominantly in the nucleus, whereas pathological TDP ‐43 is mostly found in the cytoplasm. Cytoplasmic TDP ‐43 accumulation has not yet been reported in normal general organs. In our preliminary study, paraffin sections of the general organs of individuals with or without amyotrophic lateral sclerosis ( ALS ) were immunostained with antibodies against TDP ‐43 and phosphorylated TDP ‐43 ( pTDP ‐43). Diffuse and granular immunostaining pattern of TDP ‐43 and pTDP ‐43 were observed frequently in the cytoplasm of renal tubular cells, and less frequently in the cells of several organs; however, the majority of these immunoreactivities were nonspecific biotin reactions. Conversely, many TDP ‐43‐positive and pTDP ‐43‐negative cytoplasmic accumulations were observed in the adrenal medulla in every individual (with or without ALS ). Skein‐like or round inclusions were not observed. The cells in the adrenal medulla were well preserved, and the cytoplasmic TDP ‐43 accumulations were frequent in the cells of all routine autopsy cases without loss of nuclear TDP ‐43 immunostaining; therefore, we considered that this was a physiological phenomenon. This is the first study that demonstrated the cytoplasmic accumulation of TDP ‐43 in routinely autopsied cases.