UGT is a form of gonadal dysgenesis that occurs in individuals who have a Disorder/Difference of Sex Development (DSD) that affects the differentiation of the gonad towards testis or ovary. UGT is a precursor for gonadal germ cell cancer. We hypothesize that UGT represents a state of developmental arrest of the gonad, due to co-presence of testis- and ovary-promoting signals. We will investigate this by molecular and cellular characterization of UGT. Gene expression and activated/downregulated genetic pathways will be scrutinized globally and at single cell level, and confirmed by spatial expression profiling. We will also explore the progression from UGT to gonadoblastoma and  invasive germ cell cancer. Lastly, we will investigate the 3D structure of UGT, focusing on cellular interactions, tubule formation and vascularization. We hope to increase our understanding of atypical human gonadal differentiation and of the earliest steps that lead to gonadal germ cell cancer in DSD.