Racial variation in the O‐acetylation phenotype of human colonic mucosa

Abstract

O‐acetylated and non‐O‐acetylated sialoglycoproteins can be distinguished by the mPAS (mild periodic acid‐Schiff) histochemical technique. Individual adults show one of three different patterns of staining of large intestinal mucosa: uniformly mPAS‐positive, uniformly mPAS‐negative, or mPAS‐negative with scattered mPAS‐positive crypts. To test our hypothesis that these variations are the results of a single autosomal gene (oat) polymorphism, we have studied the frequency of the three patterns of staining in a total of 435 adult colon specimens from six geographically separate populations: British, South African blacks, Icelanders, Japanese, Hong 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 uniformly mPAS‐negative cases; this distribution differed significantly (X², Poat) controlling O‐acetylation of sialic acid, probably by an O‐acetyl transferase enzyme. 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 enzymes differ between the Sino‐Japanese and non‐Sino‐Japanese races. This newly described gene polymorphism may be related to differential susceptibility to organisms binding specifically to either O‐acetylated or non‐O‐acetylated sialoglycoproteins, or to differential enteric colonization by bacterial flora that vary in their relative secretion of sialidases and sialate O‐acetyl esterase.