PTTG1 and Cowden disease: In the first study, in a zebrafish model, PTTG gene overexpression was induced by the transposition to a full-length PTTG gene of a proximal promoter of proopiomelanocortin (POMC) gene, which regulates the expression of pro-opiomelanocortin (POMC), the ACTH precursor, and it resulted in dysregulated and uncontrolled cell proliferation in two (33.3%) of six cases, leading to a neoplastic lesion, strongly resembling the human corticotroph tumor, and representing a model of CD.