Investigating the pathophysiology of Amyotrophic Lateral Sclerosis using human induced pluripotent stem cell technology
Date
06/2016Author
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Abstract
Amyotrophic Lateral Sclerosis (ALS) is a devastating, adult onset, neurodegenerative
disease which remains largely untreatable and incurable, reflecting an incomplete
understanding of the key pathogenic mechanisms that underlie motoneuron (MN) loss
in the disease. Through the use of induced pluripotent stem cell (iPSCs) technology,
cells from the human central nervous system can be studied at a range of time points,
including those prior to overt pathology, in order to understand early causative events
in ALS. In the present study, human iPSC-derived MNs and astrocytes were used to
study the pathophysiology of ALS. Whole-cell patch clamp recording techniques
were utilised to investigate whether the functional properties of human iPSC-derived
MNs are altered in cells derived from ALS patients compared to those from healthy
controls. Patient iPSC-derived MNs harbouring C9ORF72 or TARDBP mutations
display an initial period of hyperexcitability followed by a progressive loss of action
potential output due to decreases in voltage-activated Na+ and K+ currents. These
changes occur in the absence of changes in cell viability. Given evidence in support of
non-cell autonomous disease mechanisms in ALS, the potential involvement of
interactions between neurons and astrocytes in the pathophysiological phenotype were
next investigated. Patient iPSC-derived astrocytes harbouring C9ORF72 or TARDBP
G298S mutations cause a loss of functional output in control iPSC-derived MNs, due
to a progressive decrease in voltage-activated Na+ and K+ currents. These data show
that patient iPSC-derived astrocytes can induce pathophysiological changes in control
human iPSC-derived MNs which are similar to those revealed in patient iPSC-derived
MNs. This study also utilizes pharmacological agents and genetic editing to
demonstrate that the pathophysiological phenotype can be altered. Overall, this study implicates MN dysfunction, potentially due to non-cell autonomous disease
mechanisms, as an early contributor to downstream degenerative pathways that
ultimately lead to MN loss in ALS.
Type
Thesis, PhD Doctor of Philosophy
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