Genome complexity: how are stem cells directed? (Introduction)

by David Turell @, Tuesday, July 07, 2020, 19:47 (1360 days ago) @ David Turell

More of the mystery solved:

https://phys.org/news/2020-07-rna-key-stem-cells.html

"How does a stem cell—the raw material with which our organ and tissue cells are made—know what to become?

"In a study published July 8, University of Colorado Boulder researchers come one step closer to answering that fundamental question, concluding that the molecular messenger RNA (ribonucleic acid) plays an indispensable role in cell differentiation, serving as a bridge between our genes and the so-called "epigenetic" machinery that turns them on and off.

***

"'All genes are not expressed all the time in all cells. Instead, each tissue type has its own epigenetic program that determines which genes get turned on or off at any moment," said co-senior author Thomas Cech, a Nobel laureate and distinguished professor of biochemistry. "We determined in great detail that RNA is a master regulator of this epigenetic silencing and that in the absence of RNA, this system cannot work. It is critical for life."

***

"In a landmark paper in Cell, Rinn showed that inside the nucleus, RNA attaches itself to a folded cluster of proteins called polycomb repressive complex (PRC2), which is believed to regulate gene expression. Numerous other studies have since found the same and added that different RNAs also bind to different protein complexes.

***

"'RNA seemed to be playing the role of air traffic controller, guiding the plane—or protein complex—to the right spot on the DNA to land and silence genes," said Long.

"For a third step, they used the gene-editing technology known as CRISPR to develop a line of stem cells destined to become human heart muscle cells but in which the protein complex, PRC2, was incapable of binding to RNA. In essence, the plane couldn't connect with air-traffic control and lost its way, and the process fell apart.

"By day 7, the normal stem cells had begun to look and act like heart cells. But the mutant cells didn't beat. Notably, when normal PRC2 was restored, they began to behave more normally."

Comment: Obviously a carefully designed system which had to overcome the problem in sexual reproduction resulting in one cell with all the instructions. Thousands of different cells have to be produced and isolated and organized into their proper organs by a process called embryology we are barely beginning to understand. Designer absolutely required


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