Speaker
Description
Cells protect themselves against heat stress through a variety of highly conserved mechanisms to prevent protein damage and maintain cellular integrity and function. The most studied response to rapid increases of temperature is the heat shock response (HSR), which triggers the expression of heat shock proteins (HSPs), which then act as chaperones
to prevent protein misfolding. While the HSR is well-studied in single cells, much less is known about whether in multicellular organisms, the HSR is purely cell-autonomous and whether the HSR can, for instance, be induced or modulated by systemic inputs such as the neuronal perception of heat.
In C. elegans, temperature perception is mediated by the AFD neuron, located in the head of the animal. To what extent AFD activity is involved in the HSR across tissues is still a subject of research. Most approaches have focused on either abolishing AFD activity or
genetic ablation of the neuron. However, fewer teams have tried to obtain physiological activation of the AFD neurons by increasing the temperature only in the anterior region of the worms. Does exposing the head to HS-inducing temperatures produce the same effects as full body heat shocks?
To address this question, we developed a long-term imaging platform to immobilize adult worms and apply a steep temperature gradient along the antero-posterior axis of the worm. We used a microfluidics solution based on the WormSpa chip by Kopito and Levine [1], that we position on a coverslip patterned with transparent micro-heaters made from Indium Tin Oxide (ITO). Using high-resolution infrared camera measurements, we show that with optimized micro-heater patterns, temperature gradients up to 12K/mm can be achieved within our device. Thus, our setup allows us to control the temperature within C. elegans at the microscale across the animal, while permitting high resolution live imaging in immobilized animals. To characterize potentially non cell-autonomous dynamics of the C. elegans HSR we use two reporter strains: 1) Endogenously-tagged GTBP-1::RFP [2] and 2) Endogenously-tagged HSP90-mCherry (provided by Eric Cornes). By first applying uniform temperature increases across animals we identified tissue-specific dynamics of our HSR reporters. For instance,
accumulation of GTBP-1 in stress granules in intestinal cells and embryos takes between 4 to 10 min and requires temperatures of 29 to 31°C. However, a similar response in the germline and mature oocytes takes longer (10-20 min) requires higher temperatures (32-34°C). Interestingly, we did not observe such tissue specific differences in activation times for HSP-90.
Preliminary results using our temperature gradient setup indicate that stress granules appear only in the region exposed to the high temperature for both germline and embryos. However, the intestinal cells show stress granule formation along the entire body, even in animal parts not subjected to heat shock. Our results indicate that the HSR is highly tissue-specific and neuronal inputs may modulate its dynamics only in a subset of tissues.
- Kopito., et al . (2014) LOC 14.4:764-770, doi: 10.1039/C3LC51061A.
- Lee., et al. (2020) Elife e52896, doi: 10.7554/eLife.52896.
| Would you be interested in attending the pre-conference courses? | Yes |
|---|