N). PCs exhibited stronger immunolabelling with DAB in control (G) than ET case (H). Scale bar: 200 mm. Higher magnification confocal images of PCs stained with LC3 and Alexa 488 showed that controls (I, J) contained more LC3 puncta than ET cases (K, L). Scale bar: 50 mm. Using image J, we further analyzed the percentage of PC body occupied by AVs (M ). The percentage of PC body occupied by AVs was significantly lower in ET cases than controls (P). We further divided our 80-49-9 site samples into three groups including controls, short duration ET group, and long duration ET group and compared the LC3-II clustering. LC3-II clustering was highest 
in the controls and lowest in the long duration ET group (Q). A cerebellar cortical section was stained with calbindin (R, red) and LC3 (S, green) in a case of ET. A PC body (arrow) and an axonal torpedo (asterisk) were identified by the positive calbindin staining (R). Axonal torpedo did not display any LC3 staining (S, T). Scale bar: 50 mm. doi:10.1371/journal.pone.0053040.gbeclin-1 level in ET cerebellum, consistent with an early step of autophagic failure, which further sets ET apart from other neurodegenerative disorders such as AD, PD, HD, or DLB [15,20,28,30]. By forming the core complex required for AV formation, beclin1 is an important player in the induction of macroautophagy [25]. Deficiency in beclin-1 has been observed in post-mortem AD brains and spinocerebellar ataxia type 3 (SCA3) patients’ fibroblasts [31,32]. Furthermore, beclin-1 is recruited to Htt inclusions in HD mouse model brains and in the striatum in HDpatients, in which the reduced availability of beclin-1 might result in cell death [33]. Lentiviral delivery of beclin-1 in AD, PD, and SCA3 mouse models results in removal of amyloid b (Ab), asynuclein, and ataxin-3 aggregates, respectively [16,31,32]. Finally, beclin-1 plays an important role in PC degeneration, as mutated GluRd in lurcher mice binds to nPIST and recruits beclin1, which triggers autophagic cell death in PCs [34]. Together, these studies suggest that beclin-1 is an important regulator in neurodegenerative diseases.Autophagy in Essential TremorFigure 3. Mitochondrial accumulation and beclin-1 deficiency in ET cerebellum. Levels of mitochondrial membrane protein, TIM23 and TOMM20, in cerebellar cortex homogenates in 10 ET cases and 23727046 11 controls were determined by Western blot and the representative bands were shown (A). TIM23 and TOMM20 were normalized against b-actin to determine the protein levels. TIM23 and TOMM20 protein levels were significantly higher in the cerebellum of ET cases than controls (B, C). In contrast, TIM23 and TOMM20 protein levels were similar in the occipital cortex of 7 ET cases and 9 controls (D ). S6K, pS6K, and beclin-1 levels in cerebellar cortex homogenates were determined by Western blot (G). pS6K levels were highly variable (G). pS6K and S6K ratio did not differ between ET cases and controls (H). Beclin-1 level was significantly lower in ET cases than controls (I). doi:10.1371/journal.pone.0053040.gThe early steps of macroautophagy also involve two important cellular machinery proteins, Atg5 and Atg7 [35], which are required for AV formation and LC3-II clustering [36,37]. Interestingly, Atg5 or Atg7 PC-specific deficient mice, which lack macroautophagy in PCs, showed age-dependent PC loss and PC axonal terminal Mirin web swelling [36,37]. In contrast with other mutant mice 
with PC degeneration, these mice only exhibit moderate PC loss and mild ataxia.N). PCs exhibited stronger immunolabelling with DAB in control (G) than ET case (H). Scale bar: 200 mm. Higher magnification confocal images of PCs stained with LC3 and Alexa 488 showed that controls (I, J) contained more LC3 puncta than ET cases (K, L). Scale bar: 50 mm. Using image J, we further analyzed the percentage of PC body occupied by AVs (M ). The percentage of PC body occupied by AVs was significantly lower in ET cases than controls (P). We further divided our samples into three groups including controls, short duration ET group, and long duration ET group and compared the LC3-II clustering. LC3-II clustering was highest in the controls and lowest in the long duration ET group (Q). A cerebellar cortical section was stained with calbindin (R, red) and LC3 (S, green) in a case of ET. A PC body (arrow) and an axonal torpedo (asterisk) were identified by the positive calbindin staining (R). Axonal torpedo did not display any LC3 staining (S, T). Scale bar: 50 mm. doi:10.1371/journal.pone.0053040.gbeclin-1 level in ET cerebellum, consistent with an early step of autophagic failure, which further sets ET apart from other neurodegenerative disorders such as AD, PD, HD, or DLB [15,20,28,30]. By forming the core complex required for AV formation, beclin1 is an important player in the induction of macroautophagy [25]. Deficiency in beclin-1 has been observed in post-mortem AD brains and spinocerebellar ataxia type 3 (SCA3) patients’ fibroblasts [31,32]. Furthermore, beclin-1 is recruited to Htt inclusions in HD mouse model brains and in the striatum in HDpatients, in which the reduced availability of beclin-1 might result in cell death [33]. Lentiviral delivery of beclin-1 in AD, PD, and SCA3 mouse models results in removal of amyloid b (Ab), asynuclein, and ataxin-3 aggregates, respectively [16,31,32]. Finally, beclin-1 plays an important role in PC degeneration, as mutated GluRd in lurcher mice binds to nPIST and recruits beclin1, which triggers autophagic cell death in PCs [34]. Together, these studies suggest that beclin-1 is an important regulator in neurodegenerative diseases.Autophagy in Essential TremorFigure 3. Mitochondrial accumulation and beclin-1 deficiency in ET cerebellum. Levels of mitochondrial membrane protein, TIM23 and TOMM20, in cerebellar cortex homogenates in 10 ET cases and 23727046 11 controls were determined by Western blot and the representative bands were shown (A). TIM23 and TOMM20 were normalized against b-actin to determine the protein levels. TIM23 and TOMM20 protein levels were significantly higher in the cerebellum of ET cases than controls (B, C). In contrast, TIM23 and TOMM20 protein levels were similar in the occipital cortex of 7 ET cases and 9 controls (D ). S6K, pS6K, and beclin-1 levels in cerebellar cortex homogenates were determined by Western blot (G). pS6K levels were highly variable (G). pS6K and S6K ratio did not differ between ET cases and controls (H). Beclin-1 level was significantly lower in ET cases than controls (I). doi:10.1371/journal.pone.0053040.gThe early steps of macroautophagy also involve two important cellular machinery proteins, Atg5 and Atg7 [35], which are required for AV formation and LC3-II clustering [36,37]. Interestingly, Atg5 or Atg7 PC-specific deficient mice, which lack macroautophagy in PCs, showed age-dependent PC loss and PC axonal terminal swelling [36,37]. In contrast with other mutant mice with PC degeneration, these mice only exhibit moderate PC loss and mild ataxia.
