Rescue of myocytes and locomotion through AAV2/9-2YF intracisternal gene therapy in a rat model of creatine transporter deficiency

Creatine de fi ciency syndromes (CDS), caused by mutations in GATM (AGAT), GAMT , and SLC6A8 , mainly affect the central nervous system (CNS). CDS show brain creatine (Cr) de fi ciency, intellectual disability with severe speech delay, behavioral troubles, epilepsy, and motor dysfunction. AGAT/GAMT-de fi cient patients lack brain Cr synthesis but express the Cr transporter SLC6A8 at the blood -brain barrier and are thus treatable by oral supplementation of Cr. In contrast, no satisfactory treatment has been identi fi ed for Cr transporter de fi ciency (CTD), the most frequent of CDS. We used our Slc6a8 Y389C CTD rat model to develop a new AAV2/9-2YF -driven gene therapy re-establishing the functional Slc6a8 transporter in rat CNS. We show, after intra-cisterna magna AAV2/9-2YF-Slc6a8-FLAG vector injection of postnatal day 11 pups, the transduction of Slc6a8-FLAG in cerebellum, medulla oblongata, and spinal cord as well as a partial recovery of Cr in these brain regions, together with full prevention of locomotion defaults and impairment of myocyte development observed in Slc6a8 Y389 C/y male rats. While more work is needed to correct those CTD phenotypes more associated with forebrain structures, this study is the fi rst demonstrating positive effects of an AAV -driven gene therapy on CTD and thus represents a very encouraging approach to treat the so -far untreatable CTD.