Neurexin 1 (NRXN1) Deletions in Schizophrenia

Over the last 2 years, several reports have suggested that submicroscopic chromosomal deletions that disrupt the gene neurexin 1 (NRXN1) increase the risk of developing schizophrenia. In this article, we will review the evidence for this association. NRXN1 encodes NRXN1, a synaptic neuronal adhesion molecule. NRXNs are found presynaptically and are believed to interact with postsynaptic neuroligins (NLGNs) in excitatory and inhibitory synapses in the brain. The structure and possible function of NRXNs and NLGNs have recently been comprehensively reviewed.1 Vertebrate NRXNs and NLGNs are the only adhesion molecules for which a specifically synaptic function has been demonstrated.1 Current evidence suggests that NRXNs and NLGNs act transsynaptically to mediate essential signaling between presynaptic and postsynaptic specializations. Evidence from cell culture experiments and the study of mouse knockouts suggest that these molecules are required for synapse function but not for synapse formation, that they influence transsynaptic activation of synaptic transmission; and that their dysfunction impairs the properties of synapses and disrupts neural networks without completely abolishing synaptic transmission. NRXNs and NLGNs probably function by binding to each other and by interacting with intracellular proteins (most notably those with PDZ domain), but the precise mechanisms involved remain unknown.1 Whatever the mechanism and their relationship to synaptic function, it is clear that mice lacking NRXNs or NLGNs show marked deficits in synaptic transmission.1 There are 5 NLGN genes and 3 NRXN genes in humans (NRXN1 [2p16.3], NRXN2 [11q13], NRXN3 [14q31]). The 3 NRXN genes each encode an α protein and a β protein from independent promoters. NRXNs have a striking molecular diversity: the messenger RNA can be processed by alternative splicing, giving potentially thousands of distinct protein isoforms.2