Molecular cloning and characterization of two zebrafish alpha(1,3)fucosyltransferase genes developmentally regulated in embryogenesis

Some alpha(1,3)fucosylated oligosaccharides serve as counter receptors to l ectin-like adhesion proteins or are expressed with temporal precision durin g embryogenesis, and alpha(1,3)fucosyltransferase is a key enzyme in the pr oduction of these oligosaccharides. Two alpha(1,3)fucosyltransferase genes, designated zFT1 and zFT2, were cloned from zebrafish, Sequence comparisons with other genes indicated that zFT1 and zFT2 share about 30% amino acid s equence identity with human alpha(1,3)fucosyltransferases. Although the alp ha(1,3)fucosyltransferases cloned so far can be classified into three types -myeloid, Lewis, and leukocyte-by virtue of their amino acid sequences, phy logenetic analysis indicated that neither zFT1 nor zFT2 belongs to any of t hese categories. The expression of zFT1 or zFT2 in mammalian cells induces alpha(1,3)fucosyltransferase activity to synthesize the Lewis x structure f rom pyridyl-aminated lacto-N-neotetraose however, lacto-N-tetraose does not serve as a substrate. Reverse transcriptase-polymerase chain reaction anal ysis revealed that zFT1 is transcribed during a restricted period before ha tching, whereas the mRNA for zFT2 was detected only after hatching.