Neuroligin 2 Is Required for Synapse Development and Function at theDrosophilaNeuromuscular Junction

Abstract

Neuroligins belong to a highly conserved family of cell adhesion molecules that have been implicated in synapse formation and function. However, the precise in vivo roles of Neuroligins remain unclear. In the present study, we have analyzed the function of Drosophila neuroligin 2 (dnl2) in synaptic development and function. We show that dnl2 is strongly expressed in the embryonic and larval CNS and at the larval neuromuscular junction (NMJ). dnl2 null mutants are viable but display numerous structural defects at the NMJ, including reduced axonal branching and fewer synaptic boutons. dnl2 mutants also show an increase in the number of active zones per bouton but a decrease in the thickness of the subsynaptic reticulum and length of postsynaptic densities. dnl2 mutants also exhibit a decrease in the total glutamate receptor density and a shift in the subunit composition of glutamate receptors in favor of GluRIIA complexes. In addition to the observed defects in synaptic morphology, we also find that dnl2 mutants show increased transmitter release and altered kinetics of stimulus-evoked transmitter release. Importantly, the defects in presynaptic structure, receptor density, and synaptic transmission can be rescued by postsynaptic expression of dnl2. Finally, we show that dnl2 colocalizes and binds to Drosophila neurexin (dnrx) in vivo. However, whereas homozygous mutants for either dnl2 or dnrx are viable, double mutants are lethal and display more severe defects in synaptic morphology. Altogether, our data show that, although dnl2 is not absolutely required for synaptogenesis, it is required postsynaptically for synapse maturation and function.

Cooperation of Syd-1 with Neurexin synchronizes pre- with postsynaptic assembly

“…Nonetheless, severe deficits in the in vivo assembly of Drosophila NMJ synapses [11][12][13] were reported for mutants of Nrx-1 and Nlg1 (for domain organization, see Fig. 1a).…”

Adult Neurogenesis and Psychiatric Disorders

“…Furthermore, significant numbers of dentate gyrus granule cells were histologically and electrophysiologically immature, more than would be predicted based on proliferation rates and the tempo of normal development, and these mice showed severe impairments in working memory . Neurexins (NRXNs) and neuroligins (NLGNs) are families of synaptic proteins, which are known to be risk factors for schizophrenia (Novak et al 2009;Rujescu et al 2009;Ikeda et al 2010;Gauthier et al 2011;Mozhui et al 2011;Sun et al 2011;Yue et al 2011). These proteins are synaptic cell-adhesion molecules involved in various neuronal processes, including differentiation, maturation, stabilization, and plasticity of both inhibitory and excitatory synapses (Bang and Owczarek 2013).…”

Drosophila Neuroligin3 Regulates Neuromuscular Junction Development and Synaptic Differentiation

“…Generation of dnlg3 Null Mutant-The Ends-out technology used to knock out the dnlg3 gene was described previously (20,23). Briefly, two pairs of primers (5Ј-ATCCGTACGGGCAAT-GAAGAGAAGCAGAT-3Ј and 5Ј-ATCGGCGCGCCCTGC-TGCGTTTTCTGAATGC-3Ј; 5Ј-ATCGGTACCCTGTCAC-CTGTCTGCCCTTT-3Ј and 5ЈATCGCGGCCGCGTTGCT-GCTCCATTCCCACG-3Ј) were used to amplify two homologous fragments (upstream arm, Ϫ4739 to Ϫ1556; downstream arm, 2293-5243) of the dnlg3 locus from w 1118 genomic DNA.…”

“…The procedure for Western blot analysis was described previously (20). In brief, adult fruit fly heads, ventral nerve cord (VNC), and muscle filament were homogenized with 1ϫ SDS loading buffer (50 mM Tris-HCl, 2% SDS, 0.1% bromphenol blue, 10% glycerol, 1% ␤-mercaptoethanol), and the total protein lysates were separated on an 8% SDS-polyacrylamide gel and electrotransferred onto polyvinylidene difluoride membranes.…”

“…Similar to mammals, the Drosophila also has four Nlgs (dnlg1-4) (19,20). We and others have previously shown that although DNlg1 is specifically expressed at NMJs, DNlg2 is expressed in both NMJs and CNS, and loss of either dnlg1 or dnlg2 causes deficits in bouton development (i.e.…”