Cell biological analysis of CACH/VWM leukodystrophy

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DESCRIPTION (provided by applicant): Diseases of militated white matter tracts in the central nervous system (CNS) represent one of the most frequent neurological disorders. Those known to be inheritable are referred to as leukodystrophies. In many instances the identification of specific genetic lesions has helped explain the pathology observed in patients. This has not been the case for the recently identified mutations in the subunits of translation initiation factor 2B (eIF2B) in patients diagnosed with autosomal recessive Childhood Ataxia with Diffuse CNS Hypomyelination (CACH)/Vanishing White Matter Disease (VWM; MIM 603896). The lack of a suitable experimental system in which to directly test the effect of elF2B mutations on the biology of neural cell populations is a major obstacle in understanding the etiology of CACH/VWM disease. By applying our extensive experience in the isolation and culture of neural stem ceils and progenitors from both the rodent and human CNS, we established cultures of ceils with the characteristics of neural precursors from the brain of a CACH/VWM disease patient with known mutations in the epsilon subunit of elF2B (EIF2B5). This is the first example of an in vitro system using primary ceils directly isolated from a leukodystrophy patient. Analysis of these cultures using lineage specific markers revealed the presence of neurons, oligodendrocytes and astrocytes. In light of the clinical pathology, we initially focused on the oligodendrocyte compartment. Contrary to our expectations, oligodendrocytes derived from the patient's brain appeared normal by morphological criteria and progressive maturation of oligodendroglial lineage cells could be observed. However, only few glial fiballry acidic protein (GFAP) expressing cells were present and most of these ceils exhibited an atypical morphology. Also, the induction of GFAP + astrocytes using otherwise highly pro-astrocytic conditions was severely impaired. This suggests that a mutation in eIF2B5 leads to a defect in the formation of astrocytes in CACH/VWM disease. This does not preclude that oligodendrocytes may also be directly affected. However, the possibility that a deficiency in astrocyte function may contribute to the loss of white matter in CACH/VWM leukodystrophy in a non autonomous manner has important consequences for therapeutic strategies. The goal of the proposed research is to exploit this unique in vitro system to study the biological effects of eiF2B5 mutations on different CNS lineages in CACH/VWM disease patients.