SBF2 and X-linked myotubular myopathy: The major source of PtdIns5P in human cells comes from the action of the myotubularins, a family of phosphoinositide 3-phosphatases associated to different diseases: X-linked centronuclear myopathy (MTM1), Charcot-Marie-Tooth CMT4B1 (MTMR2), CMT4B2 (MTMR13) and CMT4B3 (MTMR5) [46,70].