Lessons from GNE-deficient embryonic stem cells: sialic acid biosynthesis is involved in proliferation and gene expression.

Sialic acids are widely expressed as terminal carbohydrates on glycoconjugates of eukaryotic cells. They are involved in a variety of cellular functions, such as cell adhesion or signal recognition. The key enzyme of sialic acid biosynthesis is the bifunctional UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE), which catalyzes the first two steps of sialic acid biosynthesis in the cytosol. Inactivation of GNE causes early embryonic lethality. In this study, we analyzed wild-type and GNE-deficient embryonic stem cells from mice. We found for the first time that proliferation is directly correlated with GNE-expression and the cellular sialic acid concentration. Furthermore, we identified growth-related genes that are differentially expressed in GNE-deficient embryonic stem cells compared to wild-type embryonic stem cells.