Our research focuses on Schaaf-Yang syndrome (SYS), an ultra rare neurodevelopmental disease caused by truncating mutations in the MAGEL2 gene. Particularly, in this study we explore how these mutations affect the localization of the MAGEL2 protein within cells. By heterologous expression of tagged proteins we found that the truncated forms tend to accumulate more in the nucleus of cells, compared to the healthy version. Notably, mutations associated with a more severe phenotype show a stronger tendency for this mislocalization. Our findings hint at the possibility that this abnormal localization might play a role in the severity of SYS symptoms, potentially paving the way for new research strategies and treatment. (https://jmg.bmj.com/content/early/2024/03/28/jmg-2024-109898 )