Investigators at the UCLA have recently determined that induced pluripotent stem cells (iPSC) apparently retain an inactive X chromosome even after they are reverted to a stem state from their adult form.

This was recently made obvious as adult human skin cells were reprogrammed to become female iPSC. The research team noticed that the resulting cell population still featured the inactive chromosome.

Studying iPSC is of critical importance for regenerative medicine, especially when considering that researching the most powerful type of stem cells, the embryonic variety, is forbidden at this point.

Pluripotent stem cells are basically adult cell populations that are reverted back to a state from which they can redevelop into virtually any type of cell present in the human body.

This embryonic-like ability is less extensive than the one actual embryonic stem cells (ESC) have, but it meets the “job requirements” for many practical applications.

The team of experts that conducted the new investigation is based at the University of California in Los Angeles' (UCLA) Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research.

Researchers here were led by expert Kathrin Plath. She is also the senior author of a new study detailing the findings, which appears in the September 3 issue of the esteemed journal Cell Stem Cell.

“We knew from our studies that in reprogrammed mouse cells, the X chromosome becomes active again,” Plath explains.

“The question we wanted to ask is, what happens in female human iPS cells?” says the expert, who is also an UCLA assistant professor of biological chemistry.

The scientist is also one of the first in the world to reprogram mouse and human adult cells into iPS cells.

The new discoveries could conceivably be used to gain more data on diseases such as Rett syndrome. The condition is a nervous system disorder, triggered by mutations in a gene located on the X chromosome.

“The presence of the inactive X chromosome in the iPS cells raised the question of which of the two X chromosomes is inactive in the iPS cell lines,” the team leader adds.

“For studies of X-linked diseases with female iPS cells, one needs to be careful about which X chromosome is expressed,” Plath concludes.
 
Funds for this investigation were secured from the California Institute for Regenerative Medicine, the US National Institutes of Health (NIH) and the UCLA Broad Stem Cell Research Center.