NLGN3 autism variants have distinct functional impact on synapses and sleep behavior in Drosophila.

Loss of the fly homolog Nlg3 altered sleep patterns, synaptic architecture, and vesicle dynamics, and these phenotypes were rescued by expression of the human NLGN3 reference allele.

• Phenotypes were assessed in Drosophila Nlg3 loss-of-function models.
• Rescue with human NLGN3Ref indicated functional conservation between fly Nlg3 and human NLGN3.
• The abstract does not give effect sizes or p-values for these phenotypes.

The p.R175W variant (de novo, identified in a heterozygous female with ASD) and the maternally inherited p.R451C variant altered synapse morphology with minimal effects on vesicle dynamics.

• Variants were modeled as transgenic Drosophila lines expressing the human variant alleles.
• Phenotypes were compared in the loss-of-function (rescue) context against NLGN3Ref.
• The abstract gives no quantitative detail on the magnitude of the morphology changes.

The maternally inherited p.R597W variant (associated with sleep disorder and ASD) altered sleep and vesicle dynamics with minimal impact on synapse morphology.

• This pattern is the reverse of the p.R175W and p.R451C pattern, which affected synapse morphology but not vesicle dynamics.
• The variant was identified in a male proband with sleep disorder and ASD.

Overexpression of human NLGN3Ref altered sleep patterns and synaptic morphology in flies.

• This showed that increased NLGN3 dosage is itself sufficient to cause phenotypes.
• The overexpression models served as a baseline for comparing variant effects.

In overexpression models, the p.R175W variant exacerbated sleep phenotypes, and both p.R175W and p.R451C exacerbated synapse morphology phenotypes relative to the reference allele.

• The exacerbation beyond NLGN3Ref overexpression supports gain-of-function properties.
• The abstract does not report numerical effect sizes.

The de novo p.R175W variant from a heterozygous female appears to have gain-of-function properties, while maternally inherited variants have context-dependent functional impact.

• This conclusion rests on the combination of loss-of-function rescue and overexpression experiments.
• The maternally inherited variants studied were p.R451C and p.R597W.

Some NLGN3 variants disrupt synaptic development while others alter synaptic function, suggesting differential effects that may reflect heterogeneity among individuals with ASD.

• Variants separated into morphology-dominant (p.R175W, p.R451C) and sleep/vesicle-dominant (p.R597W) phenotypic profiles.
• The authors suggest these functional differences may provide insight into ASD heterogeneity.