The complete nucleotide sequence of the cDNA coding for rat GD3-synthase was determined for the first time using PCR and the rapid amplification of cDNA ends (RACE) procedures. The deduced amino acid sequence consists of 359 residues. The protein contains a potential transmembrane domain with a short N-terminus and such highly conserved regions as the sialylmotifs. An antisense oligonucleotide derived from the rat GD3-synthase cDNA was applied to the cultures of rat cerebellar neurons and results showed a decrease in the synthesis of ganglioside GD3, indicating that the expression of GD3-synthase was modulated by the antisense sequence.