VWM astrocyte in culture.
The complexity and plasticity of the mammalian nervous system have been major obstacles in identifying the cell biological processes that result in the manifestation of a disease. This is particularly true for genetic diseases, in which the causative mutations may have been identified, but the consequences at the cellular or tissue level remain unclear, thereby dramatically limiting our ability to devise effective therapies.
My laboratory is particularly interested in the effects of genetic mutation on the function of human glial precursor cells. The successful isolation and continued propagation of human neural precursors has only recently been accomplished and the realization that genetic diseases may have their origin in the disruption of lineage development is a very new concept. The research conducted in my lab has provided the first example of a devastating genetic disease of the CNS from whom the precursor cells of an afflicted patient have been isolated, a cellular phenotype was identified and recreated by targeting the appropriate protein in normal human neural precursors. These studies were conducted on one of the heritable leukodystrophies for which identification of mutations per se has not provided insights into cellular pathophysiology. The autosomal recessive Childhood Ataxia with Diffuse CNS Hypomyelination (CACH) (also known as Vanishing White Matter Disease VWM) is associated with mutations in the subunits of translation initiation factor 2B (eIF2B), yet the lack of a suitable experimental system in which to directly test the effect of eIF2B mutations has been a major obstacle in understanding the etiology of CACH/VWM disease.
VWM disrupt glial precursor differentiation.
We have discovered that neural precursors from the brain of a CACH/VWM disease patient with known mutations in the e subunit of eIF2B (EIF2B5) are specifically compromised in their ability to generate astrocytes. Analysis of early cultures derived from the CNS of a VWM disease patient, 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 in culture. Surprisingly, however, only few glial fibrillary acidic protein (GFAP) expressing cells were present and most of these cells exhibited an atypical morphology. In addition, generation of GFAP+ astrocytes from precursor cells was severely impaired, even under conditions known to promote astrocyte differentiation.
VWM disrupt glial precursor differentiation.
Using patient-derived cells to generate inducible, pluripotent stem cells (iPSCs), we have now developed a Disease in a Dish model of VWM. In collaboration with the Department of Neurology at Massachusetts General Hospital (Harvard), we will use these in vitro cell models to screen for candidate therapeutic compounds that can ameliorate the cell biological defects in neural lineage cells.