In particular, dysregulation of MMP-9 is known to influence cognitive processes (Beroun et al., 2019) and increased MMP-9 levels are associated with several neurodevelopmental disorders including ASD (Abdallah et al., 2012; Yoo et al., 2016), fragile X syndrome (Dziembowska et al., 2013; Sidhu et al., 2014), epilepsy (Konopka et al., 2013), bipolar disorder (Rybakowski et al., 2013), and schizophrenia (Yamamori et al., 2013). Here, MMP9 is linked to fragile X syndrome.