Functional changes in connectivity induced by differential manipulations of activity in Drosophila tonic versus phasic motoneurons

Structural and functional plasticity induced by neuronal competition is a common feature of developing nervous systems. However, the rules governing how postsynaptic cells differentiate between presynaptic inputs are unclear. In this thesis, I characterized synaptic interactions following manipulations of Ib tonic or Is phasic glutamatergic motoneurons that co-innervate postsynaptic muscles at Drosophila neuromuscular junctions (NMJs). After identifying drivers for each neuronal subtype, I performed ablation or genetic manipulations to alter neuronal activity and examined the effects on synaptic innervation and function. Ablation of either Ib or Is resulted in decreased muscle response, with some functional compensation occurring in the tonic Ib input when Is was missing. In contrast, the phasic Is terminal failed to show functional or structural changes following loss of the co-innervating Ib input. Decreasing the activity of the Ib or Is neuron with tetanus toxin light chain resulted in structural changes in muscle innervation. Decreased Ib activity resulted in reduced active zone (AZ) number and decreased postsynaptic subsynaptic reticulum (SSR) volume, with the emergence of filopodial-like protrusions from synaptic boutons of the Ib input. Decreased Is activity did not induce structural changes at its own synapses, but the co-innervating Ib motoneuron increased the number of synaptic boutons and AZs it formed. These findings indicate tonic and phasic neurons respond independently to changes in activity, with either functional or structural alterations in the tonic motoneuron occurring following loss or reduced activity of the co-innervating phasic input, respectively. This thesis work contributes to the understanding of how multiple neuronal inputs innervating one postsynaptic muscle interact.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Biology

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2020

Author dc:creator

• Aponte Santiago, Nicole Ann.

Advisor dc:contributor.advisor

• J. Troy Littleton.

• Biology.

Statement dc:rights

• MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/130188

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/130188