Not all neuroligin 3 and 4X missense variants lead to significant functional inactivation.

INTRODUCTION: Neuroligins are postsynaptic cell adhesion molecules that interact with neurexins to regulate the fine balance between excitation and inhibition of synapses. Recently, accumulating evidence, involving mutation analysis, cellular assays, and mouse models, has suggested that neuroligin (NLGN) mutations affect synapse maturation and function. Previously, four missense variations [p.G426S (NLGN3), p.G84R (NLGN4X), p.Q162K (NLGN4X), and p.A283T (NLGN4X)] in four different unrelated patients have been identified by PCR and direct sequencing.

METHODS: In this study, we analyzed the functional effect of these missense variations by in vitro experiment via the stable HEK293 cells expressing wild-type and mutant neuroligin.

RESULTS: We found that the four mutations did not significantly impair the expression of neuroligin 3 and neuroligin 4X, and also did not measurably inhibit the neurexin 1-neuroligin interaction. These variants might play a modest role in the pathogenesis of autism or might simply be unreported infrequent polymorphisms.

CONCLUSION: Our data suggest that these four previously described neuroligin mutations are not primary risk factors for autism.