Abstract
BackgroundHuntington’s Disease (HD) is a devastating neurodegenerative disorder that clinically manifests as motor dysfunction, cognitive impairment and psychiatric symptoms. There is currently no cure for this progressive and fatal disorder. The causative mutation of this hereditary disease is a trinucleotide repeat expansion (CAG) in the Huntingtin gene that results in an expanded polyglutamine tract. Multiple mechanisms have been proposed to explain the preferential striatal and cortical degeneration that occurs with HD, including non-cell-autonomous contribution from astrocytes. Although numerous cell culture and animal models exist, there is a great need for experimental systems that can more accurately replicate the human disease. Human induced pluripotent stem cells (iPSCs) are a remarkable new tool to study neurological disorders because this cell type can be derived from patients as a renewable, genetically tractable source for unlimited cells that are difficult to acquire, such as neurons and astrocytes. The development of experimental systems based on iPSC technology could aid in the identification of molecular lesions and therapeutic treatments.ResultsWe derived iPSCs from a father with adult onset HD and 50 CAG repeats (F-HD-iPSC) and his daughter with juvenile HD and 109 CAG repeats (D-HD-iPSC). These disease-specific iPSC lines were characterized by standard assays to assess the quality of iPSC lines and to demonstrate their pluripotency. HD-iPSCs were capable of producing phenotypically normal, functional neurons in vitro and were able to survive and differentiate into neurons in the adult mouse brain in vivo after transplantation. Surprisingly, when HD-iPSCs were directed to differentiate into an astrocytic lineage, we observed the presence of cytoplasmic, electron clear vacuoles in astrocytes from both F-HD-iPSCs and D-HD-iPSCs, which were significantly more pronounced in D-HD-astrocytes. Remarkably, the vacuolation in diseased astrocytes was observed under basal culture conditions without additional stressors and increased over time. Importantly, similar vacuolation phenotype has also been observed in peripheral blood lymphocytes from individuals with HD. Together, these data suggest that vacuolation may be a phenotype associated with HD.ConclusionsWe have generated a unique in vitro system to study HD pathogenesis using patient-specific iPSCs. The astrocytes derived from patient-specific iPSCs exhibit a vacuolation phenotype, a phenomenon previously documented in primary lymphocytes from HD patients. Our studies pave the way for future mechanistic investigations using human iPSCs to model HD and for high-throughput therapeutic screens.
Highlights
Huntington’s Disease (HD) is a devastating neurodegenerative disorder that clinically manifests as motor dysfunction, cognitive impairment and psychiatric symptoms
Derivation and characterization of HD-induced pluripotent stem cells (iPSCs) lines To derive the iPSC lines, we retrovirally introduced the four reprogramming factors (Oct3/4, Sox2, c-MYC and Klf4) [26,27] into dermal fibroblasts harvested from a male patient with adult onset HD (50 CAG repeats), his daughter with juvenile-HD (109 CAG repeats) and non-related neonatal foreskin fibroblasts (28 CAG repeats) as controls
Colonies generated from all three fibroblast cell lines exhibited typical iPSC morphology (Figure 1A), similar to conventional human embryonic stem cells (hESCs) lines and maintained a normal karyotype after continuous expansion (Figure 1B)
Summary
Huntington’s Disease (HD) is a devastating neurodegenerative disorder that clinically manifests as motor dysfunction, cognitive impairment and psychiatric symptoms. The causative mutation of this hereditary disease is a trinucleotide repeat expansion (CAG) in the Huntingtin gene that results in an expanded polyglutamine tract. Huntington’s disease (HD) is a fatal, progressive, neurodegenerative disorder that affects approximately 1 in 10,000 people [1]. The genetic defect for this autosomal dominant disorder is a trinucleotide repeat expansion (CAG) in exon 1 of huntingtin (HTT), which results in an expanded polyglutamine tract at the N-terminal of the HTT protein [3]. Mutant HTT aggregates have been detected in other neural cell types such as astrocytes in the brain of HD patients [8,9]. Other areas of the brain, such as the hippocampus, are affected [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
