DRA is functionally linked to NHE3 and is expressed in a low-to-high gradient from the proximal to distal colon in rodents.28 DRA has been shown to be downregulated at the protein but not mRNA level in mice intrarectally instilled with TcdA, but this has not been assessed during infection.20 Immunofluorescence analysis revealed that DRA expression was significantly decreased in the distal colon in response to functional TcdA or TcdB, with no additive outcome when both functional toxins were present (Figures 5c,d and Supplementary Figure S4). The gene discussed is SLC9A3; the disease is infection.