For example, reduction in the number of inhibitory synapses and over-activation of class I metabotropic glutamate receptor in the cerebral cortex and hippocampus due to lack of a modulator of voltage gated calcium channel Cav2.2 called Fragile X Mental Retardation 1(fmr1) gene results in fragile X syndrome in mice. Here, FMR1 is linked to fragile X syndrome.