RT Journal Article
SR Electronic
T1 Differentiation of human induced pluripotent or embryonic stem cells decreases the DNA damage response
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 094938
DO 10.1101/094938
A1 Kalpana Mujoo
A1 Raj K. Pandita
A1 Anjana Tiwari
A1 Vijay Charaka
A1 Sharmistha Chakraborty
A1 Walter N. Hittelman
A1 Nobuo Horikoshi
A1 Clayton R. Hunt
A1 Kum Kum Khanna
A1 Alexander Y. Kots
A1 E. Brian Butler
A1 Ferid Murad
A1 Tej K. Pandita
YR 2016
UL http://biorxiv.org/content/early/2016/12/18/094938.abstract
AB Genomic integrity is critical for preservation of stem cell function and is, maintained through a robust DNA damage response (DDR) with systemized DNA DSB repair by either the non-homologous end joining (NHEJ) pathway or the homologous recombination (HR) pathway. To examine DDR during stem cell differentiation, human embryonic (hES) and induced pluripotent stem (IPS) cells were exposed to DNA damaging agents and DNA damage signaling/repair measured. Differentiated cells displayed a higher frequency of residual DNA damage, chromosomal aberrations, cells with delayed γ-H2AX foci disappearance and a reduced number of RAD51 foci. Factors impacting DNA DSB repair by HR formed reduced foci in differentiated cells. The reduction in repairosome foci formation after DNA damage was not due to changes in HR protein levels, which were unchanged by differentiation. Differentiated cells also displayed a higher frequency of stalled DNA replication forks and decreased firing of new replication origins from transient inhibition of DNA synthesis by hydroxyurea treatment. In addition, we observed that differentiated cells exhibit a higher frequency of R-loops. A similar decline in DDR was observed as early stage mouse astrocytes differentiated into later stage astrocytes. Our studies thus suggest that DSB repair by homologous recombination is increasingly impaired during stem cell differentiation while the NHEJ pathway is minimally altered.