The Japan Academy

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Vol. 88 No. 4 (2012)

Vol. 88 No. 4 (2012)

Extensive expression of a novel glycolipid, phosphatidylglucoside, in astroglial lineage cells in fetal cerebral cortex

  The lipid raft hypothesis has a wide impact on the field of cell biology and has provided a novel insight into dynamic structure of biological membrane. In 2001, Hirabayashi and his colleagues (Nagatsuka et al., FEBS Lett., 2001) discovered a novel glycolipid, phosphatidylglucoside (PtdGlc), in human umbilical cord red blood cells and HL60 cells, and they later identified it as a lipid raft-resident glycolipid (Nagatsuka et al., Biochemistry, 2006).
  PtdGlc in rodent fetal brains was purified and its complete chemical structure was successfully determined. The fatty acid composition of PtdGlc is unique in that the sn-1 chain is exclusively stearic acid (C18:0) and the sn-2 chain is arachidic acid (C20:0). PtdGlc is a constituent of distinct microdomains or lipid rafts on the outer leaflet of the plasma membranes. It is intensively expressed in the germinal zones of the central nervous system of C57BL/6 mice (Kinoshita et al., Biochem J., 2009; Kaneko et al., J. Neurochem., 2011). During early development of the embryonic cerebral cortex (˜E17), the expression of PtdGlc (in green) consistently co-locates with that of brain lipid binding protein (BLBP) (in red), a radial glia-specific antigen, in the germinal ventricular (VZ) and subventricular (SVZ) zones. In contrast, newborn cortical neurons that finished migrating up to the cortical plate (CP) show diminished PtdGlc expression. Instead, PtdGlc expression is shifted from the radial glia to a subpopultion of astroglial cells, which co-expresses the typical astroglial antigen, glial fibrillary acidic protein (GFAP) in the CP. The expression profile suggests that PtdGlc-domains or lipid rafts act as a signaling platform for astroglial differentiation. One of water soluble PtdGlc metabolites, lyso-PtdGlc, has potent activities in growth cone collapse of developing neurons, suggesting important roles in neuronal network formation.
  Reproduced with permission, from Kinoshita et al., 2009, Biochem. J. 419, 565 © the Biochemical Society.

Kunihiko Suzuki
Member of the Japan Academy