Scientists find out why living things are the size they are -- and none other

Apr 07, 2010

If you consider yourself to be too short or too tall, things are looking up, or down, depending on your vertical disposition. New research published online in The FASEB Journal explains how we grow, how our bodies maintain correct proportions, and offers insight into what goes wrong with growth disorders and unregulated cell growth in cancer.

"We hope that these insights into the mechanisms controlling body will help us understand better the reasons for the excessive growth of and also provide new approaches to turn growth back on in normal cells in order to regenerate damaged organs," said Julian C. Lui, Ph.D., a researcher involved in the work from the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health in Bethesda, Maryland.

Scientists studied which genes were active in young animals (growing rapidly) and compared them to the same genes in older animals (growing slowly). Then they identified which genes were "turned off" simultaneously in multiple organs with age. To understand the consequences of these genes being turned off, the researchers experimentally turned them off in and observed the effects.

They found that rapid growth in early life is a response to the activation of multiple genes that stimulate growth. These same genes are progressively turned off during the maturation process, causing growth to slow. This process occurs simultaneously in multiple organs, which explains why organs all stay in proportional size as the body grows. This process is not controlled by age. Instead, are turned off when organs achieve a certain level of growth.

"This important work answers the question of why any animal- including us - has a certain size," said Gerald Weissmann, M.D., Editor-in-Chief of The , "As this study shows, growth is dictated by organ development, and no one wishes their organs to be abnormally large or small."

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More information: Julian C. Lui, Patricia Forcinito, Maria Chang, Weiping Chen, Kevin M. Barnes, and Jeffrey Baron. Coordinated postnatal down-regulation of multiple growth-promoting genes: evidence for a genetic program limiting organ growth. FASEB J. doi:10.1096/fj.09-152835

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out7x
not rated yet Apr 08, 2010
So what makes the genes turn off?
hush1
not rated yet Apr 08, 2010
genes are turned off when organs achieve a certain level of growth.


@out7x

To answer your question - it was the researchers that turned them off experimentally. Every cell has researchers in them, that turn growth on or off just at the right times. :)

It is the mysterious word "level" in the quote above.
Of course no one knows where, how, when or what expressions of "level" take place.

It is as if the on-off switch for size and growth are independent from time.

Actually the whole article implies time, explicitly and implicitly.

I'm implying I don't understand the writers' report of the authors work.
PinkElephant
not rated yet Apr 08, 2010
no one wishes their organs to be abnormally large or small.
Um... I dunno, I'm pretty sure at least half of that statement is at least partially false, with respect to at least half the human population (the male half...)
jsa09
Apr 09, 2010
This comment has been removed by a moderator.