MTOR and pheochromocytoma: Evidence also suggests that mTOR signaling may be driven by loss-of-function TMEM127 (transmembrane protein 127) mutations in some cases: germline TMEM127 mutations have been identified in a proportion of familial phaeochromocytomas, and in around 2% of apparently sporadic disease, with loss of heterozygosity in tumor specimens (143, 144).