Babies face sudden and severe starvation right after birth - after they have lost their nutrient supply from the placenta but before they have started to drink milk. They survive this period, researchers show in an online publication by Nature, by feeding on the contents of their own cells.
Studying newborn mice, Noboru Mizushima and his colleagues show that a cellular process called autophagy ramps up immediately after birth and remains high for several hours. During autophagy, a cell breaks down components of its own cytoplasm in small digestive sacs called autophagosomes.
Mice genetically engineered so that they cannot form autophagosomes die within one day of birth, the researchers show, and their levels of amino acids are markedly reduced. The authors suggest that autophagy is essential immediately after birth for the production of amino acids, which are used either as an energy source or as building blocks for new proteins.
Noboru Mizushima (The Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan)
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