Aggregates of the protein tau are the hallmark of several neurodegenerative diseases including Alzheimer’s disease, frontotemporal lobar degeneration (FTLD-tau), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), Pick’s disease, and chronic traumatic encephalopathy (CTE). Another protein, TDP-43, comprises aggregates which are the primary hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP). To model tau or TDP-43 proteinopathies, transgenic C. elegans have been generated that express the full-length human protein pan-neuronally. These worms exhibit significant uncoordinated movement on plates and impaired thrashing in liquid. To assay differences in total activity, we used a WMicroTracker ARENA System.
All worms used were staged by way of timed egglay, and grown at 16oC on NGM plates seeded with OP50 E. coli to day 1 adult. The experiment was performed in a 6-well plate prepared with 3.5mL NGM per well and seeded with OP50. The worms were picked from stock plates into a prepared 6-well plate, 30 worms per strain, each strain in a unique well. Recordings were performed at room temperature (approximately 22oC). The plate was placed in the ARENA 15 minutes before starting the run to allow worms to acclimate. 14 activity scores were collected per strain over 60 minutes. Statistical analysis was performed with GraphPad Prism 8.
Tau and TDP-43- expressing worms had significantly less activity per minute than N2 (Figure 1). Further, we found the ARENA- assessed activity data recapitulated the relative severity of phenotypes among the strains as measured by motility assays. For example, both CK10 (tau V337M) and CK144 (tau WT) have significantly uncoordinated movement when crawling or thrashing in liquid, with CK144 having worse motility than CK10, due to its much higher burden of total tau protein expressed. Likewise, CK410 (TDP-43 WT) worms have slightly impaired motility compared with N2 when crawling on a plate, CK423 (TDP-43 M337V) are severely uncoordinated, and CK426 (TDP-43 A315T) have the most severe uncoordinated phenotype. The relative toxicities of these strains stem from the effects of the mutations, as TDP-43 protein expression is relatively even among these transgenic strains. Interestingly, the ARENA captures activity of these severely uncoordinated worms that move poorly in motility assays such as crawling on an NGM plate or thrashing in liquid. Therefore, ARENA assessment of aggregate activity may be a more accurate metric for capturing non-locomotor movement of C.elegans that are severely uncoordinated.
MicroPubl Biol. 2020 Jul 16;2020:10.17912/micropub.biology.000278. doi: 10.17912/micropub.biology.000278.
Heather N Currey, Anna Malinkevich, Penny Melquist and Nicole F Liachko.