ALK and fragile X syndrome: Additionally, jeb and alk mutants exhibit synaptic structural changes consistent with this FMRP interaction, including a larger NMJ area and synaptic bouton maturation defects (Rohrbough et al., 2013), which are markedly similar to the structural overelaboration phenotypes of the FXS disease state (Gatto and Broadie, 2011; Tessier and Broadie, 2012).