RACIAL VARIATION IN THE O-ACETYLATION PHENOTYPE OF HUMAN COLONIC MUCOSA

O-acetylated and non-O-acetylated sialoglycoproteins can be distinguis hed by the mPAS (mild periodic acid-Schiff) histochemical technique. I ndividual adults show one of three different patterns of staining of l arge intestinal mucosa: uniformly mPAS-positive, uniformly mPAS-negati ve, or mPAS-negative with scattered mPAS-positive crypts. To test our hypothesis that these variations are the result of a single autosomal gene (oat) polymorphism, we have studied the frequency of the three pa tterns of staining in a total of 435 adult colon specimens from six ge ographically separate populations: British, South African blacks, Icel anders, Japanese, I-long Kong Chinese, and Bahrainis. The distribution of the three types of staining fell into two groups. In Japanese and Chinese, uniformly mPAS-positive cases were;much more frequent than un iformly mPAS-negative cases; this distribution differed significantly (chi(2), P<0.001) from that in non-Sino-Japanese, where the uniformly mPAS-positive phenotype was much less frequently found than the unifor mly mPAS-negative phenotype. In neither of the groups did the frequenc y of the three phenotypes differ significantly from that predicted for a single gene polymorphism by the Hardy-Weinberg law. The variation i n staining patterns between populations is consistent with variation i n frequency of a single polymorphic autosomal gene (oat) controlling O -acetylation of sialic acid, probably by an O-acetyl transferase enzym e. Loss of function mutation in the high acetylator gene (oat(a)) in a colonic crypt stem cell in heterozygous individuals would account for the scattered discordant crypts. Gene frequencies for a variety of en zymes differ between the Sino-Japanese and non-Sino-Japanese races. Th is newly described gene polymorphism may be related to differential su sceptibility to organisms binding specifically to either O-acetylated or non-O-acetylated sialoglycoproteins, or to differential enteric col onization by bacterial flora that vary in their relative secretion of sialidases and sialate O-acetyl esterases.