RHEB and fleck corneal dystrophy: To assess whether the TSC complex can convert RHEBp.P37L from its active GTP- to its inactive GDP-bound state, we compared the effects of transient in vitro overexpression of the RHEBp.P37L mutant with wild-type RHEB (RHEB WT) and the RHEBp.S16H mutant, a well-known gain-of-function mutant of RHEB recently used to generate an FCD mouse model [20,22].