Mouse beta 1,3-galactosyltransferase (GA1/GM1/GD1b synthase): Protein characterization, tissue expression, and developmental regulation in neural retina

The composition of cell surface gangliosides is largely dependent: on the r elative activities of Golgi resident glycosyltransferases. In the brain of birds and mammals, complex gangliosides (GM2, GM1, GD1a, GD1b, GT1b) abound at late stages of development and in the adult, due to the relatively high activities of the UDP-GalNAc:LacCer/GM3/GD3 beta 1,4-N-acetylgalactosaminy ltransferase (GalNAc-T) and the UDP-Gal: GA2/GM2/GD2 beta 1,3-galactosyltra nsferase (Gal-T2) relative to that of CMP-NeuAc:GM3 alpha 2,8-sialyltransfe rase (Sial-T2), Unlike brain, the mature mammalian neural retina abundantly expresses the simple ganglioside GD3, in relation to complex gangliosides, due to the low activity of GalNAc-T and Gal-T2 relative to Sial-T2, Here w e describe the isolation and characterization of a mouse Gal-T2 cDNA that d rives the synthesis of an epitope-tagged protein of molecular mass 43 kDa, which was enzymatically active and localized to the Golgi complex in transf ected cell lines. Using this cDNA as a probe, it was found that Gal-T2 is c oded by a single gene located in chromosome 17, and that the coding sequenc e is contained in a single exon, The expression of the specific Gal-T2 mRNA (similar to 1.8 kb) was highest: in testis, which also showed elevated Gal -T2 activity, In the postnatal neural retina, Gal-T2 mRNA increased after d ay 3, maintained high levels of expression by days 4-7, and then decreased to initial values by day 10, The developmental pattern of mRNA expression w as temporally coincident with that of Gal-T2 activity expression, indicatin g that this enzyme is under transcriptional control in the neural retina. ( C) 1999 Wiley-Liss, Inc.