Backgound. Amyotrophic lateral sclerosis (ALS) is progressive neurodegenerative disease characterized by the loss of motor function. Several ALS genes have been identified as their mutations can lead to familial ALS, including the recently reported RNA-binding protein fused in sarcoma (Fus). However, it is not clear how mutations of Fus lead to motor neuron degeneration in ALS. In this study, we present a Drosophila model to examine the toxicity of Fus, its Drosophila orthologue Cabeza (Caz), and the ALS-related Fus mutants. Results: Our results show that the expression of wild-type Fus/Caz or FusR521G induced progressive toxicity in multiple tissues of the transgenic flies in a dose- and age-dependent manner. The expression of Fus, Caz, or FusR521G in motor neurons significantly impaired the locomotive ability of fly larvae and adults. The presynaptic structures in neuromuscular junctions were disrupted and motor neurons in the ventral nerve cord (VNC) were disorganized and underwent apoptosis. Surprisingly, the interruption of Fus nuclear localization by either deleting its nuclear localization sequence (NLS) or adding a nuclear export signal (NES) blocked Fus toxicity. Moreover, we discovered that the loss of caz in Drosophila led to severe growth defects in the eyes and VNCs, caused locomotive disability and NMJ disruption, but did not induce apoptotic cell death. Conclusions: These data demonstrate that the overexpression of Fus/Caz causes in vivo toxicity by disrupting neuromuscular junctions (NMJs) and inducing apoptosis in motor neurons. In addition, the nuclear localization of Fus is essential for Fus to induce toxicity. Our findings also suggest that Fus overexpression and gene deletion can cause similar degenerative phenotypes but the underlying mechanisms are likely different.
|State||Published - 2012|
Bibliographical noteFunding Information:
We thank Mary K. Brewer for technical assistance, and Drs. Hongge Jia and Jiayu Zhang for making some of the Fus/Caz constructs. We thank the Bonini Lab for providing a detailed protocol of the fly eye paraffin section. We thank Dr. Brian McCabe for the caz1 mutant. We thank the Developmental Studies Hybridoma Bank (DSHB) for antibodies and the Bloomington Stock Center for Drosophila strains. This work was in part supported by the National Institutes of Health grants (R01NS077284, R01NS049126 and R21AG032567 to HZ), the ALS Association (6SE340 to HZ), and the Center of Biomedical Research Excellence in the Molecular Basis of Human Disease (COBRE, P20RR020171).
ASJC Scopus subject areas
- Molecular Biology
- Clinical Neurology
- Cellular and Molecular Neuroscience