RNF5 and cystic fibrosis: Conversely, RNF5 was more strongly associated with fat mass than fat-free mass, suggesting that its altered expression can contribute to CF phenotypic variation, as these individuals are known to have bile and other digestive issues, including difficulties in assimilating fat (Bijvelds et al., 2005; Freudenberg et al., 2008; Morison et al., 1997; Wilke et al., 2011).