Catalyzes the synthesis of lactosylceramide (LacCer) via the transfer of galactose from UDP-galactose to glucosylceramide (GlcCer) (By similarity). Required for proper patterning of the dorsoventral axis during embryogenesis through the regulation of BMP signaling (PubMed:16672343). Plays a role in proteoglycan glycosylation that is required for BMP-dependent specification of the dorsoventral axis (PubMed:16672343). a beta-D-glucosyl-(1<->1')-N-acylsphing-4-enine + UDP-alpha-D-galactose = a beta-D-Gal-(1->4)-beta-D-Glc-(1<->1)-Cer(d18:1(4E)) + H(+) + UDP Protein modification; protein glycosylation. Sphingolipid metabolism. Trans cisternae of Golgi stack. Expressed by the early epiboly stage and reaches a steady state level of expression by mid-somitogenesis (PubMed:16672343). Shows widespread expression throughout the embryo during the first 24 hours of development, with enhanced expression within several structures at the 20-somite stage (PubMed:16672343). Morpholino knockdown results in dorsalized embryos which have ventrally expanded chordin expression and reduced activation of the Bmp-dependent transcription factors smad1/5/8 (PubMed:16672343). Proteoglycans exhibits defective glycosylation and a greatly reduced affinity for bmp2 (PubMed:16672343). Belongs to the glycosyltransferase 7 family.