Temporal changes of gene expression in mouse heart, kidney and lung during juvenile growth

Temporal changes of gene expression from 1-wk- to 4-wk and 8-wk-old mouse in heart, kidney and lung. Mammalian somatic growth is rapid in early postnatal life but then slows and eventually ceases in multiple tissues. We hypothesized that there exists a postnatal gene expression program that is common to multiple tissues and is responsible for this coordinate growth deceleration. Consistent with this hypothesis, microarray analysis identified >1600 genes that were regulated with age coordinately in kidney, lung, and heart of juvenile mice, including many genes that regulate proliferation. As examples, we focused on three growth-promoting genes, Igf2, Mest, and Peg3, that were markedly downregulated with age. We conclude that there exists an extensive genetic program occurring during postnatal life. Many of the involved genes are regulated coordinately in multiple organs, including many genes that regulate cell proliferation. At least some of these are themselves apparently regulated by growth, suggesting that, in the embryo, a gene expression pattern is established that allows for rapid somatic growth of multiple tissues but then, during postnatal life, this growth leads to negative-feedback changes in gene expression that in turn slow and eventually halt somatic growth, thus imposing a fundamental limit on adult body size. To compare gene expression between fast-growing animals and more slowly growing animals, we extracted total mRNA from kidney and lung in 1-wk, 4-wk, and 8-wk-old mice (5 animals each).