PTGS1 and colorectal carcinoma: We identified a significant reduction in relative abundance of cells double-positive for tuft cell markers PTGS1/POU2F3 and choline acetyltransferase ChAT/POU2F3 in individuals that were homozygous for CRC risk allele at rs3087967 (TT, n=4) compared with homozygous non-risk (CC, n=7) samples (p=0.042 for both stains) (figure 5).