islocalization of TDP-43 in the G93A mutant SOD1 transgenic ouse model of ALS

Previous evidence demonstrates that TAR DNA binding protein (TDP-43) mislocalization is a key pathological feature of amyotrophic lateral sclerosis (ALS). TDP-43 normally shows nuclear localization, but in CNS tissue from patients who died with ALS this protein mislocalizes to the cytoplasm. Disease specific TDP-43 species have also been reported to include hyperphosphorylated TDP-43, as well as a C-terminal fragment. Whether these abnormal TDP-43 features are present in patients with SOD1-related familial ALS (fALS), or in mutant SOD1 over-expressing transgenic mouse models of ALS remains controversial. Here we investigate TDP-43 pathology in transgenic mice expressing the G93A mutant form of SOD1. In contrast to previous reports we observe redistribution of TDP-43 to the cytoplasm of motor neurons in mutant SOD1 transgenic mice, but this is seen only in mice having advanced disease. Furthermore, we also inal version published as: Shan, X. , Vocadlo, D. , & Krieger, C. (2009). Mislocalization of TDP-43 in the G93A mutant OD1 transgenic mouse model of ALS. Neuroscience Letters, 458(2), 70–74. https://doi.org/10.1016/j.neulet. 2009.04. 031 observe rounded TDP-43 immunoreactive inclusions associated with intense ubiquitin immunoreactivity in lumbar spinal cord at end stage disease in mSOD mice. These data indicate that TDP-43 mislocalization and ubiquitination are present in end stage mSOD mice. However, we do not observe C-terminal TDP-43 fragments nor TDP-43 hyperphosphorylated species in these end stage mSOD mice. Our findings indicate that G93A mutant SOD1 transgenic mice recapitulate some key pathological, but not all biochemical hallmarks, of TDP-43 pathology previously observed in human ALS. These studies suggest motor neuron nt SO degeneration in the muta myotrophic lateral sclerosis (ALS) is a neurodegenerative disease electively affecting motor neurons of the brainstem and spinal ord, as well as cortical regions. Approximately 5–10% of ALS cases re inherited (fALS), however, the cause of the remaining 90–95% of poradic ALS (sALS) cases remains unknown. Mutations of superoxde dismutase 1 (SOD1) account for approximately 15–20% of fALS ases (1–2% of all ALS cases), whereas various other gene mutations ccount for only a small subset of the remaining fALS cases [9]. Nerous system tissue from patients who died with fALS and sALS has een extensively studied to gain insight into the pathological feaures of ALS. To study the pathogenesis and investigate the details of he progression of ALS, transgenic rodent models harboring fALSssociated mutations in human mutant SOD1 (mSOD) have been eveloped. These models have proven to be of significant value 8] and replicate several key features observed in both sALS and ∗ Corresponding author at: Department of Molecular Biology and Biochemistry, imon Fraser University, 8888 University Dr., Burnaby, British Columbia V5A 1S6, anada. Tel. : +1 778 782 3530; fax: +1 778 782 3765. ∗∗ Corresponding author. Tel. : +1 778 782 3753; fax: +1 778 782 3040. E-mail addresses: dvocadlo@sfu.ca (D. Vocadlo), ckrieger@sfu.ca (C. Krieger). D1 transgenic mice is associated with TDP-43 histopathology. fALS including progressive loss of motor neurons, neurofilament aggregation, and the accumulation of cytoplasmic ubiquitinated inclusions (UBIs) within degenerating motor neurons [5,20]. Recently, two independent groups [1,14] have reported that TAR DNA binding protein (TDP-43), a nuclear DNA and RNA binding protein proposed to function as a regulator of transcription [16] and alternative splicing [2,13] is present in UBIs in sALS. Furthermore, a number of TDP-43 mutations have been reported in both sALS and fALS cases, suggesting that TDP-43 may play a causal role in the pathogenesis of ALS [19,22,23]. TDP-43 is normally localized to the nucleus, however, in CNS tissue from patients who died with ALS, TDP-43 is redistributed from the nucleus to the cytoplasm, where it appears to be distributed diffusely, or to aggregate as a component of UBIs [1,14]. Although studies of TDP-43 in human ALS cases are generally consistent [1,4,12,14], some aspects of the TDP-43 pathology remain controversial. For instance, Mackenzie et al. [11] suggest that abnormal localization of TDP-43 is present in most sALS and fALS cases but is absent in fALS caused by SOD1 mutations. In contrast, Robertson et al. [17] showed, in two fALS cases carrying SOD1 mutations, that there is mislocalization of TDP43 to the cytoplasm as well as association with UBIs. Studies of some lines of mSOD mouse models have claimed that there is no TDP-43