ERCC1 and Cowden syndrome 1: In order to test in vivo whether the inhibition of DYRK1A through harmine treatment could alleviate progeroid pathologies, we analyzed the loss of photoreceptor cells in the retina of Ercc1−/− mice, a hallmark of CS that can also be observed in NER-deficient mice, by performing TUNEL staining of the outer nuclear layer (ONL) of the retina63.