HIF1A and Dowling-Degos disease 1: Furthermore, IF staining showed significantly higher expression levels of carboxymethyl lysine (CML) in EP and AF tissue of Vhl cKO mice compared with the levels in control mice at the age of 8 months, indicating high levels of oxidative protein damage (Fig. 6m, p, q).44 These findings show that aberrant Hif1α activation in Vhl cKO mice induced mitochondrial dysfunction during DDD progression.