Summary
The FUT2 (Secretor) gene encodes an α-1,2-fucosyltransferase responsible for expressing ABO histo-blood group antigens on gastrointestinal mucosa and in bodily secretions. Individuals carrying at least one functional allele are "secretors"; those homozygous for loss-of-function mutations are "non-secretors."
The variant
About 20% of Europeans are non-secretors (homozygous for the inactive sese allele, most commonly W143X / G428A in Caucasians). The variant is a simple SNP (rs601338), testable with most consumer genotyping platforms.
Why it matters
Non-secretors have increased susceptibility to Crohn's disease, altered microbiota composition (less diverse, different dominant species), different colonization patterns for many probiotics, different infection-risk profiles for pathogens that bind FUT2-dependent structures (norovirus, H. pylori, certain E. coli), and higher rates of B12 malabsorption.
Clinical implication
FUT2 genotype is a simple SNP test that changes the interpretation of a patient's mucosal-disease picture substantially. For a clinician working up a mucosal/IBD picture, secretor status is a low-cost data point that can shift differential weighting.
Key sources
McGovern et al 2010 (https://pubmed.ncbi.nlm.nih.gov/20570966/" target="_blank" rel="noopener noreferrer" title="Open PMID:20570966 on PubMed/PMC">PMID:20570966); Rausch et al PNAS 2011; Kashyap et al PNAS 2013.