Translational regulation of Syngap1 by FMRP modulates NMDAR mediated signalling

SYNGAP1, a Synaptic Ras-GTPase activating protein, regulates synapse maturation during a critical developmental window. Heterozygous mutation in SYNGAP1 ( SYNGAP1 +/- ) has been shown to cause Intellectual Disability (ID) in children. Recent studies have provided evidence for altered neuronal protein synthesis in a mouse model of Syngap1 +/- . However, the molecular mechanisms behind the same is unclear. Here, we report the reduced expression of a known translation regulator, FMRP, during a specific developmental period in Syngap1 +/- mice. Our results demonstrated that FMRP interacts with and regulates the translation of Syngap1 mRNA. We further show that, during development, reduced translation of FMRP and this decrease in FMRP leads to a compensatory increase of Syngap1 translation in Syngap1 +/- . These developmental changes are reflected in the altered response of eEF2 phosphorylation downstream of NMDA receptor signalling. We propose a cross-talk between FMRP and SYNGAP1 mediated signalling which can also explain the compensatory effect of impaired signalling observed in Syngap1 +/- mice.