Genomic Instability Associated with p53 Knockdown in the Generation of Huntington's Disease Human Induced Pluripotent Stem Cells.

Andrew M Tidball,Bingying Han,Miles R Bryan,Asad A Aboud,Reed Chamberlin,Kevin C Ess,Aaron B Bowman,M Diana Neely,Michael Aschner,Kevin K Kumar,Atsushi Asakura

doi:10.1371/journal.pone.0150372

Andrew M Tidball, Bingying Han + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0150372

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Abstract

Alterations in DNA damage response and repair have been observed in Huntington’s disease (HD). We generated induced pluripotent stem cells (iPSC) from primary dermal fibroblasts of 5 patients with HD and 5 control subjects. A significant fraction of the HD iPSC lines had genomic abnormalities as assessed by karyotype analysis, while none of our control lines had detectable genomic abnormalities. We demonstrate a statistically significant increase in genomic instability in HD cells during reprogramming. We also report a significant association with repeat length and severity of this instability. Our karyotypically normal HD iPSCs also have elevated ATM-p53 signaling as shown by elevated levels of phosphorylated p53 and H2AX, indicating either elevated DNA damage or hypersensitive DNA damage signaling in HD iPSCs. Thus, increased DNA damage responses in the HD genotype is coincidental with the observed chromosomal aberrations. We conclude that the disease causing mutation in HD increases the propensity of chromosomal instability relative to control fibroblasts specifically during reprogramming to a pluripotent state by a commonly used episomal-based method that includes p53 knockdown.

Highlights

Huntington’s disease (HD) neuropathology results from neuronal death of neurons primarily in the caudate and putamen of the basal ganglia
We found that abnormalities most likely occurred during the reprogramming time period and that karyotypically normal HD induced pluripotent stem cells (iPSC) lines demonstrated elevated DNA damage signaling
The length of the longest CAG repeat was significantly correlated with genomic instability in the iPSC lines with p = 0.006 by binary logistic regression

Summary

Introduction

Huntington’s disease (HD) neuropathology results from neuronal death of neurons primarily in the caudate and putamen of the basal ganglia This neuronal degeneration has been well-characterized, the mechanism by which mutant Huntingtin protein expression leads to PLOS ONE | DOI:10.1371/journal.pone.0150372. Mutant Huntingtin expressing cells have been shown to be sensitive to X-rays and resistant to immortalization by the T-antigen, further implicating alterations in DNA damage response pathway and p53 signaling in HD [3, 4]. We found that abnormalities most likely occurred during the reprogramming time period and that karyotypically normal HD iPSC lines demonstrated elevated DNA damage signaling. These data further indicate underlying alterations in DNA damage and/or repair processes in HD cells

Materials and Methods

Results and Discussion

Conclusions