SLC6A8 and hyperinsulinemic hypoglycemia, familial, 4: The importance of CRT-1 in preserving intracellular creatine content is evident from the consequences of its dysfunction in creatine transporter deficiency (Braissant and Henry, 2008; Farr et al., 2020): creatine transporter deficiency arises from point mutations in the coding sequence of CRT-1; the vast majority of these mutations lead to folding deficiency of the transporter (El-Kasaby et al., 2019; Bhat et al., 2021a).