BioTechniques News
Beatrice Bowlby
Original story from the University of Lausanne (Switzerland).
Researchers uncovered a new role for the TDP-43 protein in controlling the function of microglia, the immune cells of the brain. Their study shows how the loss of this protein in microglia may contribute to the development of neurological diseases.
The biology of microglia lies at the heart of the research conducted by Rosa Chiara Paolicelli’s group, Associate Professor in the Department of Biomedical Sciences at the Faculty of Biology and Medicine of the University of Lausanne (Unil; Switzerland). While microglia are considered the primary defense of the central nervous system, they are also involved in various neurodegenerative diseases. In their latest study, the Lausanne-based team demonstrated how dysfunctional microglia can disrupt brain function and lead to motor deficits.
The brain’s ‘guardians’
Microglia are small cells belonging to the glial cell family that reside in the central nervous system (the brain, spinal cord and retina). They are the principal immune cells of the brain, often referred to as its ‘guardians’. In addition to destroying pathogenic foreign agents and fighting infections, they are also responsible for clearing dead cells and other cellular debris.
The Unil neuroscientists, in collaboration with colleagues from several Swiss and international institutions, focused their attention on the protein TDP-43. This protein is known to play a role in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and certain forms of dementia. In these disorders, TDP-43, which is normally located in the cell nucleus, becomes mislocalized to the cytoplasm, where it forms abnormal aggregates. The progressive loss of the protein from the nucleus, where it normally performs its essential functions, combined with the toxicity of the cytoplasmic aggregates, results in a loss of function and disrupts normal cellular activity. While this phenomenon has been extensively studied in neurons, its impact on microglia remains poorly understood.
“In our study, we sought to better understand what happens when TDP-43 is no longer functional in microglia, using the mouse as an experimental model,” explained Rosa Chiara Paolicelli, who led the research. “To achieve this, we genetically deleted the gene encoding this protein specifically in microglial cells. We observed that mice lacking TDP-43 in their microglia from early life stages developed motor impairments in adulthood.”
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Harmful effects at multiple levels
Using a range of imaging techniques, the researchers revealed that TDP-43 dysfunction affects the brain at several levels.
“We detected structural alterations in specific brain regions at early stages of development, as well as abnormalities in myelin, the protective sheath surrounding nerve fibers. We also identified molecular changes suggesting dysfunction in oligodendrocytes, the cells responsible for myelin production,” explained Anne-Claire Compagnion, postdoctoral researcher at the Department of Biomedical Sciences and first author of the study.
Furthermore, the study showed that microglia lacking TDP-43 lose their ability to efficiently resolve myelin abnormalities, which are naturally generated during the myelination process that occurs throughout brain development. This impairment is associated with dysfunction of a major cellular pathway known as the TREM2–DAP12 axis, which is essential for normal microglial function.
“Our findings reveal a previously unrecognized role for TDP-43 in regulating microglial function and demonstrate how its disruption could contribute to the development of neurological diseases,” concluded Rosa Chiara Paolicelli.
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