Prolactin-dependent Expression of GD1 Ganglioside, as a Component of Milk Fat Globule, in the Murine Mammary Glands

Abstract

Lactation-associated expression of GD1 alpha ganglioside in murine mammary glands was found to be due to the increasing specific activities of Gg4Cer alpha2,3- and GM1b alpha2,6-sialyltransferases in the glands from 12th day of gestation. The gene for GM1b alpha2,6-sialyltransferase, mST6GalNAcV, which was not detected in nonpregnant glands, appeared at 12th day of gestation and increased in the following gestational and lactation periods. At 3rd day of lactation, the amounts of lipid-bound sialic acid (LSA) in the mammary glands and milk of HR-1 mice were 99.3 +/- 8.5 microg per gram of dried tissue and 2.9 microg per ml, GD1 alpha comprising 64.0% and 80.5% of the total LSA, respectively, and GD1 alpha in milk was found to be preferentially distributed in the fat globule fraction. When the mammary epithelial cells at 15th day of gestation were cultured in prolactin- and epidermal growth factor (EGF)-containing media, the synthesis of fat globules and casein, together with the enhanced synthesis of GD1 alpha, were observed in the cells in prolactin medium, indicating that synthesis of GD1 alpha occurs in association with milk production as a prolactin-dependent event. Thus, GD1 alpha ganglioside, which is characteristically distributed in the cerebellar Purkinje cells of the murine brain, is supplied to neonates through the milk of the mother.