SLC4A4 and cystic fibrosis: Importantly, we also find that these four CF predicted modifiers (CLCA1, FABP1, MUC2, SLC4A4) tend to be co‐downregulated in those GTEx lung samples in which CFTR expression is low (all pairwise hypergeometric P‐values evaluating the overlap between pairs of these modifiers are < 0.05, Fig 2D).