Dr. Christina Ising

Research Area: Inflammation and cell death in Alzheimer’s disease and other tauopathies

Website: https://sfb1403.uni-koeln.de/projects/jrg-ising

1. Research Background:

Tauopathies are aging-related neurodegenerative diseases characterized by accumulation of tau in neurons in neurofibrillary tangles (NFTs). Primary tauopathies like for example Frontotemporal dementia (FTD) can develop due to mutations in the tau gene, which leads to the build-up of tau aggregates in the patient’s brain, loss of brain volume as a result of neuronal cell death and subsequent cognitive decline. Secondary tauopathies do not only contain tau aggregates, but for example additional extracellular aggregates of amyloid-beta (Ab) in amyloid plaques as seen in Alzheimer’s disease (AD), the most prevalent tauopathy. Due to the increase in life expectancy, the number of people with AD is expected to rise over 100 million by 2050, but to date, no effective treatment not to mention cure does exist for AD or other tauopathies and the underlying mechanisms still remain elusive. One common characteristic of all tauopathies is the chronic neuroinflammation present in the brains of these patients. In the innate immune system of the brain, microglia are the first line of defense. Microglia emerged as central players in the development and progression of tauopathies over the last years when several mutations in microglia-related genes were identified as risk-factors in AD and other diseases. Modifying neuroinflammation could prove a valuable treatment option in the future, but the contribution of the immune system to mechanisms in AD and specifically the effects of microglial cell death remain poorly understood.

2. Research questions addressed by the group:

While neuroinflammation is widely accepted as a contributor to AD and other tauopathies, microglial cell death in neurodegenerative diseases in general attracted little attention to date. However, work from the past years showed that AD and FTD patients as well as respective mouse models present with activation of the NLRP3 inflammasome in microglia1–3, a protein complex that induces pyroptotic cell death. My lab is interested in further elucidating the role of pyroptotic cell death in tauopathies by investigating the role of genes that are involved in this regulated cell death pathway. Furthermore, we aim to characterize other types of microglial cell death and investigate their cause and regulation. Finally, we want to elucidate the effects microglial cell death has on intraneuronal tau pathologies, neuronal loss and subsequent memory deficits. Another topic of interest is microglial senescence, a cellular state leading to expression of a distinctive partially pro-inflammatory secretory profile and resistance to cell death. Recently, the occurrence of glial senescence was identified in a tauopathy mouse model and removal of these cells alleviated tau pathology4. However, it remains unclear what causes glial senescence and how exactly it affects intraneuronal tau accumulation. To shed light on these questions, my lab is interested in the identification of the molecular switch that drives a microglia cell either into senescence or cell death. Further, we investigate how cellular senescence is affected by tau itself and how the senescence-associated secretory profile is involved in the progression of tau pathologies.

3. Possible projects:

Role of the immunoreceptor CD300lf in tauopathies

Recently, we provided evidence that the assembly and activation of the inflammasome can be induced by tau and that a Nlrp3-knockout reduces progression of tau pathology and improves cognition in tau-transgenic Tau22 mice, a tauopathy model. Interestingly, we found that genetic loss of NLRP3 increased levels of Cd300lf in the brains of Tau22 mice2. CD300lf is an inhibitory immunoreceptor present on microglia. CD300lf overexpression was shown to be neuroprotective in a model of acute brain injury5 and mice resistant to cerebral malaria had more microglial CD300lf in conjunction with an inhibited inflammatory response6. In line with this, Cd300lf-knockout (KO) increased disease severity in an autoimmune demyelination model7 and Cd300lf-KO mice showed depressive like-behavior, which was increased after an immune challenge8. However, nothing is known about the role of CD300lf in tauopathies. Therefore, this project aims to delineate the effect Cd300lf-KO has on tau with a special focus on its relation to the NLRP3 inflammasome. To this end, primary Cd300lf-KO microglia will be analyzed for the ability to assemble and activate the NLRP3 inflammasome as well as the effect of the knockout on cleavage of Gasdermin D, a protein that is responsible for forming the membrane pore, subsequently leading to IL-1beta secretion and pyroptotic cell death9. In addition, microglial phagocytosis and release of tau and cytokines by Cd300lf-KO microglia will be analyzed. To finally connect our in vitro findings to the in vivo situation, tau-transgenic Tau22 mice with a Cd300lf-KO will be used. Brains of these mice will be analyzed for NLRP3 inflammasome activation, in vivo tau phagocytosis, tau pathology and memory impairments.

4. Applied Methods and model organisms:

In this project, the PhD candidate will learn how to generate primary microglia cultures from mice and how to isolate and analyze brains from adult mice. For cell culture experiments, recombinant tau will be purified from bacteria. Cells as well as brain tissue will be analyzed by Western Blot, ELISA, quantitative PCR, flow cytometry and immunostainings. In addition, behavior tests will be performed with mice and microglia will be isolated from adult animals before analysis by flow cytometry.

5. Desirable skills and qualifications:

We are looking for a highly motivated candidate with a scientific interest in neuroinflammation and cell death. The successful applicant should be a team-oriented individual with good written and verbal communication skills in English. The applicant should have experience with cell culture and basic molecular techniques such as PCR and Western Blot. The willingness to work with mice is mandatory and a previous participation in a FELASA-certified course is a plus.

6. References:

  1. Heneka, M. T. et al. NLRP3 is activated in Alzheimer’s disease and contributes to pathology in APP/PS1 mice. Nature 493, 674–678 (2013).
  2. Ising, C. et al. NLRP3 inflammasome activation drives tau pathology. Nature 575, 669–673 (2019).
  3. Venegas, C. et al. Microglia-derived ASC specks cross-seed amyloid-β in Alzheimer’s disease. Nature 552, 355–361 (2017).
  4. Bussian, T. J. et al. Clearance of senescent glial cells prevents tau-dependent pathology and cognitive decline. Nature 562, 578–582 (2018).
  5. Peluffo, H. et al. Overexpression of the immunoreceptor CD300f has a neuroprotective role in a model of acute brain injury. Brain Pathol. Zurich Switz. 22, 318–328 (2012).
  6. Keswani, T. et al. Expression of CD300lf by microglia contributes to resistance to cerebral malaria by impeding the neuroinflammation. Genes Immun. 21, 45–62 (2020).
  7. Xi, H. et al. Negative regulation of autoimmune demyelination by the inhibitory receptor CLM-1. J. Exp. Med. 207, 7–16 (2010).
  8. Lago, N. et al. CD300f immunoreceptor is associated with major depressive disorder and decreased microglial metabolic fitness. Proc. Natl. Acad. Sci. U. S. A. 117, 6651–6662 (2020).
  9. Shi, J. et al. Cleavage of GSDMD by inflammatory caspases determines pyroptotic cell death. Nature 526, 660–665 (2015).