Many genetic mouse models have also been reported for aqueous-deficient dry eye models, including Sod1−/− and NHE8−/− (decreased goblet cell density and Muc5ac expression), NRTN−/− (decreased goblet cell density and expression of Muc1 and muc4), Klf4CN (goblet cell absence), Spdef−/− (decreased expression of Muc5ac and Muc5b), and Tet-mev-1 (induction of excessive oxidative stress associated with damage to ocular surface epithelium and reduced aqueous secretion function) [59]. This evidence concerns the gene MUC5AC and dry eye syndrome.