Evolutionary conservation and modulation of a juvenile growth-regulating genetic program

Area of Science:

• Genomics
• Developmental Biology
• Comparative Physiology

Background:

• Mammalian body size varies greatly, influenced by growth suppression timing.
• Rodent studies identified a juvenile genetic program causing rapid growth suppression.
• This program involves simultaneous downregulation of growth-promoting genes across tissues.

Purpose of the Study:

• To investigate if the juvenile genetic program is conserved in large mammals.
• To determine if the evolutionary pace of this program correlates with adult body size.

Main Methods:

• Expression microarray analysis in sheep kidney and lung.
• Comparison of gene expression data with rodent studies.
• Real-time PCR to assess the program's pace in mice, rats, and sheep.

Main Results:

• A conserved set of downregulated genes involved in cell proliferation was identified in sheep, similar to rodents.
• This multiorgan juvenile genetic program is conserved across 80 million years of mammalian evolution.
• The pace of this genetic program is slowest in sheep, intermediate in rats, and fastest in mice.

Conclusions:

• A conserved mammalian genetic program regulates growth suppression.
• Evolutionary modulation of this program's pace allows for prolonged growth in larger mammals.
• This mechanism explains how different adult body sizes are achieved across species.