FMR1 and fragile X syndrome: For example, an increased density of 3H-MPEP binding sites has been reported in the striatum of Fmr1 knockout mice (Maccarrone et al., 2010), and an increase in mGlu5 receptor expression has been found in the prefrontal cortex of patients affected by Fragile-X syndrome (Lohith et al., 2013), in the brain of children with autism (Fatemi et al., 2011), and in brain specimens of patients affected by tuberous sclerosis (Boer et al., 2008).