Knockdown of MLC1 in primary astrocytes causes cell vacuolation: a MLC disease cell model
Anna Duarri1, Miguel Lopez de Heredia, Xavier Capdevila-Nortes
1Sección de Fisiología, Departamento de Ciencias Fisiológicas II, Universidad de Barcelona, Spain.
Abstract:
Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare type of leukodystrophy, in the majority of cases caused by mutations in the MLC1 gene. MRI from MLC patients shows diffuse cerebral white matter signal abnormality and swelling, with evidence of increased water content. Histopathology in a MLC patient shows vacuolation of myelin, which causes the cerebral white matter swelling. MLC1 protein is expressed in astrocytic processes that are part of blood- and cerebrospinal fluid-brain barriers. We aimed to create an astrocyte cell model of MLC disease. The characterization of rat astrocyte cultures revealed MLC1 localization in cell-cell contacts, which contains other proteins described typically in tight and adherent junctions. MLC1 localization in these contacts was demonstrated to depend on the actin cytoskeleton; it was not altered when disrupting the microtubule or the GFAP networks. In human tissues, MLC1 and the protein Zonula Occludens 1 (ZO-1), which is linked to the actin cytoskeleton, co-localized by EM immunostaining and were specifically co-immunoprecipitated. To create an MLC cell model, knockdown of MLC1 in primary astrocytes was performed. Reduction of MLC1 expression resulted in the appearance of intracellular vacuoles. This vacuolation was reversed by the co-expression of human MLC1. Re-examination of a human brain biopsy from an MLC patient revealed that vacuoles were also consistently present in astrocytic processes. Thus, vacuolation of astrocytes is also a hallmark of MLC disease.
Insights
Megalencephalic leukoencephalopathy with subcortical cysts (MLC) involves brain swelling due to myelin vacuolation. Researchers developed an astrocyte cell model showing MLC1 protein reduction causes vacuoles, a key feature of MLC disease.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare leukodystrophy often caused by MLC1 gene mutations.
- MLC is characterized by cerebral white matter swelling and increased water content, linked to myelin vacuolation.
- MLC1 protein is crucial in astrocytic processes forming brain barriers.
Purpose of the Study:
- To establish a cellular model for studying Megalencephalic leukoencephalopathy with subcortical cysts (MLC).
- To investigate the role of MLC1 protein in astrocyte function and its relation to MLC pathology.
- To identify cellular hallmarks of MLC disease in an in vitro model.
Main Methods:
- Characterization of rat astrocyte cultures to determine MLC1 protein localization.
- Investigating the dependence of MLC1 localization on the actin cytoskeleton.
- Performing MLC1 gene knockdown in primary astrocytes to create an MLC disease model.
- Analyzing human brain biopsies for comparison with the cell model.
Main Results:
- MLC1 protein localizes to cell-cell contacts in astrocytes, dependent on the actin cytoskeleton.
- Knockdown of MLC1 in astrocytes led to the formation of intracellular vacuoles.
- Vacuolation in the cell model was reversed by re-expressing human MLC1.
- Intracellular vacuoles were also observed in astrocytic processes in human MLC patient brain biopsies.
Conclusions:
- Astrocytic vacuolation is a significant pathological feature of Megalencephalic leukoencephalopathy with subcortical cysts (MLC).
- The developed astrocyte cell model accurately reflects key aspects of MLC pathology.
- This model provides a platform for further research into MLC disease mechanisms and potential therapies.
