Abstract: The present application relates to a method of treating a subject having a condition mediated by a deficiency in myelin. This method involves selecting a subject having a condition mediated by a deficiency in myelin and expressing a transcription factor 7-like 2 (TCF7L2) protein in the selected subject under conditions effective to treat the condition. Also disclosed is a method of increasing oligodendrocyte production from glial progenitor cells. This method involves providing a population of glial progenitor cells and expressing a TCF7L2 protein in the provided population of glial progenitor cells under conditions effective to increase oligodendrocyte production compared to oligodendrocyte production absent said administering. Also disclosed is a genetic construct suitable, inter alia, for carrying out these methods.