Deletion of the creatine transporter gene in neonatal, but not adult, mice lead to cognitive deficits.

Creatine (Cr) is a guanidino compound that provides readily-available phosphate pools for the regeneration of spent ATP. The lack of brain Cr causes moderate to severe intellectual disability, language impairment, and epilepsy. The most prevalent cause of Cr deficiency are mutations in the X-linked SLC6A8 (Creatine transporter; CrT) gene, known as CrT deficiency (CTD). There are no current treatments for CTD and the mechanisms that underlie the cognitive deficits are poorly understood. One of the most critical areas that need to be addressed is if Cr is necessary for brain development. To address this concern, the Slc6a8 gene was knocked out in either neonatal (postnatal day (P)5) or adult (P60) mice. The P5 knockout mice showed deficits in the Morris water maze and novel object recognition, while there were no deficits in P60 knockout mice. Interestingly, the P5 knockout mice showed hyperactivity during the dark phase; however, when examining control mice, the effect was due to the administration of tamoxifen from P5-10. Taken together, the results of this study show that Cr is necessary during periods of brain development involved in spatial and object learning. This study also highlights the continued importance of using proper control groups for behavioral testing.\n\nTake-home messageThe learning and memory deficits seen in Slc6a8-deficient mice are likely due to the developmental loss of Cr.