Objective: To elucidate the disease-associated cellular phenotype of induced pluripotent stem cell (iPSC)-derived cortical neurons of patients affected by X-linked dystonia-parkinsonism (XDP).

Background: XDP is an X-linked neurodegenerative disorder that is exclusively found in individuals of Filipino ancestry. Due to linkage disequilibrium, all affected individuals carry the same seven genetic changes, leaving the exact genetic and molecular cause of the disease uncertain. This phenomenon emphasizes the need of a model system that recapitulates the disease phenotype on a cellular level, thus facilitating elucidation of the disease mechanism. Numerous studies on monogenic, neurodegenerative movement disorders have determined that mitochondrial dysfunction frequently plays a critical role in disease development. To this end, we examined iPSC-derived cortical neurons of XDP patients for various parameters of mitochondrial function and their susceptibility to mitochondrial stressors.

Methods: Fibroblasts of four XDP patients and four Filipino control individuals were reprogrammed, via transduction with Sendai virus containing the four factors OCT4, SOX2, KLF4, and cMYC, into iPSC lines and differentiated into mature cortical neurons. Characterization of iPSC lines and neurons concerning pluripotent and neuronal properties was carried out by immunocytochemistry and quantitative real-time PCR. Further, we performed a series of mitochondrial assays (including measurement of ATP levels, ATP synthesis rate, and membrane potential) in neurons and analyzed cells upon treatment with mitochondrial toxins for apoptosis by application of a TUNEL assay.

Results: All iPSC lines showed pluripotent hallmarks, i.e. increased gene expression and positive immunostaining of pluripotency markers as well as the potential to differentiate into all three germ layers. Characterization of the neurons with respect to cortical features confirmed the presence of different cortical layers. Most importantly, cortical neurons of patients displayed a reduced ATP synthesis rate and an increased susceptibility to stressors leading to apoptosis.

Conclusions: There is evidence that mitochondrial function is affected in neurons of XDP patients in comparison to controls warranting further studies in this newly established neuronal model.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/induced-pluripotent-stem-cell-derived-cortical-neurons-as-a-disease-model-for-x-linked-dystonia-parkinsonism/