Molecular basis for myelin deficiency in the CNS of LSH ATPase knockout mice

Oligodendrocytes are specialised cells in the brain and spinal cord, which form myelin - the insulating layer around nerve connections. Myelin protects neurons from damage and promotes the efficient transmission of information between them. The mature myelin-producing oligodendrocytes are formed from immature oligodendrocyte precursor cells (OPCs) during postnatal development and throughout adult life. However, the ability of OPCs to produce oligodendrocytes often declines with age leading to neurodegenerative disease. This age-dependent decline in the formation of oligodendrocytes has been attributed to inappropriate regulation of gene expression as well as lack of growth signals in the adult brain. Therefore, understanding how the production of oligodendrocytes is controlled is essential for improving the lifelong health and wellbeing.

The formation of mature oligodendrocytes from OPCs requires coordinated expression and silencing of many genes. We recently found that mice lacking a protein known as LSH, which regulates gene expression during development by changing the packaging of DNA in the cell nucleus, do not form normal myelin and develop tremors and seizures. Our further experiments indicate that although OPCs are present in the brain of LSH-null mice, they fail to form mature myelin-producing cells. Here we propose to investigate further the molecular basis for myelin deficiency in mice lacking LSH and to determine the mechanism by which LSH regulates gene expression during the formation of oligodendrocytes in the developing and adult brain.

Oligodendrocytes are the highly specialised myelin-forming cells of the Central Nervous System (CNS), which are essential for maintenance on axon integrity and repair of myelin damage following injury. The mature oligodendrocytes (OL) are formed in the developing CNS postnatally from migratory committed progenitors, oligodendrocyte precursor cells (OPCs), which also replenish the pool of OLs throughout life in the adult brain. Substantial evidence suggests that epigenetic regulation of gene expression, including gene activation and silencing, plays an important role in differentiation of OPCs to mature myelin-producing OLs. In contrast to gene activation, the full scale of epigenetically regulated gene silencing that accompanies differentiation of OPCs, and especially the role of DNA methylation in locking differentiated state, is yet to be fully established.
We recently generated a unique strain of mice that are deficient in chromatin remodelling ATPase LSH, a protein implicated in developmentally programmed gene silencing, deacetylation of chromatin and de novo DNA methylation, and found that the LSH-deficient mice display substantial hypomyelination of the CNS. Our further experiments suggest that although OPCs are present in the CNS of LSH-deficient mice they fail to differentiate into mature OLs. In this project, we propose to determine the epigenetic gene silencing events that occur during differentiation of oligodendrocyte lineage cells and the molecular basis for myelin deficiency in the CNS of LSH-null mice. We also propose to examine the differentiation potential of OPCs upon LSH re-expression in young and adult brain. Such knowledge is important in order to elucidate the fundamental regulatory principles that guide differentiation of oligodendrocyte lineage cells and to direct, predict and influence the outcome of therapy for patients with CNS injury, Multiple Sclerosis and age-related neurodegenerative conditions.

Who will benefit from this research? How would they benefit from this research?

(1) Scientific community: This is a basic biomedical research project and as such the primary beneficiaries of the outputs arising from this research will be from the international scientific community. How they will benefit from this research is outlined above.

(2) Non-academic beneficiaries: In longer-term, the main beneficiaries of this research will be patients with congenital ICF syndrome caused by mutations in DNMT3B and, potentially, LSH as well as patients with Multiple Sclerosis and other neurodegenerative disease conditions affecting the myelination in the CNS. The outputs of the research from this project will benefit these groups of patients by (i) increasing the level of understanding of the molecular mechanisms leading to phenotypic manifestation and (ii) by availability of model systems that can be used to determine reversibility of phenotype/disease state thus offering possibilities for translational research and therapeutic approaches, including stem cell-based therapies.

(3) Benefits to society and the UK economy: This research will provide outstanding training opportunities and acquisition of new multidisciplinary professional research skills by staff employed on the project. The project provides potential for staff to develop novel in vivo skills, computational, quantitative and personal generic skills required in the modern work environment. These training opportunities will broaden their horizon and improve their employment potential in diverse sectors. This will ensure the international competitiveness of UK biomedical research and will benefit the society and the UK economy.

(4) Beneficiaries in the area of intellectual property: Although this is a basic biomedical research project, specific areas that may lead to intellectual property include tools for data analysis, antibodies, plasmids, cell lines and assays which could be useful in a broader context.

(5) General public: The results of the project disseminated to the general public via outreach events and press-releases will benefit the general public as they will enhance the public understanding of the importance of cutting-edge MRC-funded biomedical research and the benefits that such research brings in longer-term to society and patients suffering from MS, ICF and other conditions.