Gene expression is noisy Randomness could explain
monozygotic twin phenotype differences By Cathy Holding
The random fluctuations-also known as noise-of gene
expression could account for phenotypic variations ranging
from the minor-such as different fingerprints in identical
twins-to the major, including normal embryonic development,
according to a study in the May 27 Science.
The authors, Erin K. O'Shea and Jonathan M. Raser at the
Howard Hughes Medical Institute, University of California at
San Francisco, say their measurements of noise in single
budding yeast cells suggest that noise also provides a
means, albeit temporary, of cellular adaptation to the
environment.
O'Shea and Raser cloned two-cyan and yellow-fluorescent
protein reporter genes under the control of identical
budding yeast PHO5 gene promoters to look at cell-to-cell
differences in a population of yeast cells. When all cells
express similar quantities of the fluorescent proteins at
similar times, then little variability-meaning little randomness-
in gene expression is occurring, Raser said.
"If we see substantial differences between two independent
but identical genes-if the yellow fluorescent protein
appears 30 minutes before the cyan appears [in one cell but
not in another]-then we can say that's due to randomness,
because the cell can't tell the two proteins apart at all,"
Raser, co-author of the paper, told The Scientist.
Raser said that noise contributes to variability at the
population level. "Noisy genes will have highly variable
expression at the population level, and genes that are much
less noisy will be very consistent at the population
level," he said.
The team also identified mutations that could convert a gene
from a less to a more noisy state, and vice versa, Raser
said, "so it's clearly very possible that this is something
that a cellular population can take advantage of: to evolve
to better adapt to an environment."
Read the rest at TheScientist
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Posted by Robert Karl Stonjek.