Background: Three patterns of alpha-3-fucosyltransferase activity have been described in human adult tissues with different acceptor specificity: myeloid, plasma and Lewis. Five- to ten-week embryos express the myeloid enzyme in all tissues tested, then this enzyme is replaced by plasma or Lewis enzymes, with the exception of leukocytes that continue to express the myeloid form of the enzyme in the adult. These enzymes have not been studied as yet in the developing human kidney.
Experimental design: The three different alpha-3-fucosyltransferases were studied in homogenates of mesonephros and metanephros with synthetic oligosaccharide acceptors. The oligosaccharide precursors and products of these enzymes (precursor, H, Le(a), sialyl-Le(a) and Le(b) for type 1 and precursor, H, Le(x), sialyl-Le(x) and Le(y) for type 2) were localized by immunofluorescence with specific antibodies.
Results: Only the myeloid alpha-3-fucosyltransferase is detected at 5 weeks in mesonephros and it disappears at 8 weeks. In metanephros, the myeloid enzyme alone is detected between weeks 6 and 8. The plasma enzyme then appears and only at the last trimester of gestation does the Lewis enzyme appear. Three histologic patterns that are concordant with the expression of the alpha-3-fucosyltransferases are observed: I. Inducer, S-shaped body, Bellini and calyce express Le(x) at an early stage when, only the myeloid alpha-3-fucosyltransferase is detected; II. Later, the proximal tubules and descending limbs of Henle's loop express Le(x) (week 9) and sialyl-Le(x) (week 16) when the plasma alpha-3-fucosyltransferase appears; III. Calyceal and collecting systems always express Le(x) and after week 12 Le(a) and Le(b) appear, in accordance with the late appearance of Lewis alpha-3/4-fucosyltransferase.
Conclusions: The sequential appearance of enzymes and their products suggests that during renal organogenesis the myeloid alpha-3-fucosyltransferase is progressively replaced by the plasma enzyme in the proximal tubules and later by the Lewis enzyme in Bellini's ducts and calyce.