Preserving cellular aspects of aging in patient-specific models of ALS

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Preserving cellular aspects of aging in patient-specific models of ALS Project Summary Induced pluripotent stem cell (iPSC) biology holds great promise for human ​in vitro ​neurodegenerative disease modeling because these cells can give rise to any cell in the human brain, a living “virtual brain” amenable to experimental manipulation, having the exact same genetic makeup as individual patients and displaying neurodegenerative phenotypes previously identified in postmortem and clinical samples. These “patient-specific” ​in vitro testing systems enable target discovery, drug screening and therapeutic proof of concept studies in patient cells much earlier in the translational process than is currently possible. Despite these unique advantages, the preservation of age as a key pathogenic risk factor is presently a major limitation of these systems. This is in part due to 1) the loss of age-related characteristics in cells that are rejuvenated to an embryonic state, and 2) to deficiencies in the differentiation protocols that are unable to produce mature neurons from embryonic cells. The direct, transcription factor mediated reprogramming, also known as “lineage conversion”, of patient fibroblasts into induced motor neurons represents an alternative approach for generating human neurons ​in vitro. New data from our lab, our collaborators’ and others’ show that neurons generated through lineage conversion better retain age-related and disease-associated deficits. In this 1-year feasibility study we will compare motor neurons generated by lineage conversion from fibroblasts (fib-MNs), with those generated by directed differentiation from iPSCs reprogrammed from the same fibroblast samples (iPSC-MNs). The fibroblast samples are from patients having the GGGGCC hexanucleotide repeat expansion mutation in the ​C9ORF72 ​gene, which is known to cause a form of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia, and matched controls. Our 1st hypothesis is that fib-MN transcriptomes will be significantly more similar to those of post-mortem tissue and those from ALS patients. Our collaborator Verge Genomics has created an innovative, big-data-driven ALS gene expression signature using ​public and proprietary gene expression data from 39 ALS-relevant studies that we will use in the project. Nucleocytoplasmic transport defects have emerged as one phenotype where both age and ​C9-​ALS related differences have been identified. ​Therefore, our ​2nd hypothesis is that fib-MNs will have significantly more pronounced age-related nucleocytoplasmic transport defects than iPSC-MNs as measured by immunofluorescence confocal microscopy. Taken together, these two studies would prove the principle that fib-MNs create superior ALS in-vitro testing systems retaining important, disease-relevant aspects of aging having tremendous impact ​on the iPSC banking and disease modeling fields. AcuraStem Inc. develops human cell models and assays for preclinical human validation of its own CNS therapeutics, as well as those of its development partners.