SLC37A4 (G6P translocase; a.k.a. G6PT), working together with G6Pase, transports D-glucose 6-phosphate (glucose-6P) from the cytoplasm to the ER and is known to be a causative gene of GSD-Ib, which is characterized by osteopenia, also seen in patients with GSD-Ia caused by mutations in G6Pase [120]. The gene discussed is SLC37A4; the disease is Osteopenia.