ETD

• Autism
• Creatine
• Creatine deficiency
• Creatine transporter
• Gene therapy
• neurodevelopmental disease
• Neurodevelopmental disorder

Creatine is a highly hydrophilic compound central to the creatine/phosphocreatine system, which supports high-energy phosphate transfer. Its transport across biological membranes is mediated by the creatine transporter (CrT), encoded by the X-linked SLC6A8 gene. Loss-of-function mutations cause creatine transporter deficiency (CTD), a rare neurodevelopmental disorder characterised by intellectual disability, behavioural abnormalities, autistic-like features and seizures. Current therapeutic strategies aim to restore brain creatine levels but show limited clinical efficacy. The development of effective treatments is hindered by incomplete knowledge of CrT physiology and its cell-specific distribution in the brain.
This thesis investigated a novel gene replacement construct, AAV9-FF351, designed to reproduce the physiological expression pattern of CrT through the inclusion of regulatory regions. In vivo and ex vivo analyses showed that FF351 increased brain creatine levels and improved cognitive performance in CTD mice. In parallel, a novel reporter tool was developed to investigate CrT biodistribution. The tool links GFP expression to endogenous SLC6A8 expression, enabling the identification and quantification of CrT-producing cells across different brain regions. Together, these results provide evidence supporting AAV9-FF351 as a promising therapeutic approach for CTD and establish a tool to improve the understanding of CrT physiology and its cellular distribution in the brain.