FMR1 and fragile X syndrome: There is, however, some controversy in the literature regarding ERK1/2 activation in Fmr1 KO tissue (Hu et al., 2008; Gross et al., 2010) and given its critical role in synaptic plasticity, as well as in neurodevelopment and regulation of social behaviors, Wang and colleagues (2012) decided to investigate further this question using human brain tissue obtained from FXS patients.