Medulloblastoma is a pediatric cancer of the brain and is the most common solid tumour in children. Currently, the standard therapy for medulloblastoma remains nonspecific to the cancer subtype and consists of surgery followed by chemotherapy and/or craniospinal irradiation. Due to these treatments, affected children are left with permanent side effects such as severe neurological deficits. The development of some medulloblastoma tumours depends on the signalling pathway of a molecule known as Sonic hedgehog (Shh). This project aims to explore how tumour suppressor mutations collaborate with Shh signalling to promote tumor formation. Gaining a better understanding of how these genes act on medulloblastoma tumourigenesis may lead to the development of novel and more effective targeted therapies to treat medulloblastoma. Hopefully the identification of these new therapeutic targets will improve the survival and quality of life of the patients.