Hunchback activates Bicoid in Pair1 neurons to regulate synapse number and locomotor circuit function

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• Neural circuit assembly is crucial for behavior and depends on neuronal identity.
• Temporal patterning via transcription factors (TFs) in neural progenitors shapes neuronal diversity.
• The role of these mechanisms in postmitotic neurons remains largely unknown.

Purpose of the Study:

• Investigate the function of Drosophila temporal TF Hunchback and homeodomain TF Bicoid in the Pair1 descending neuron circuit.
• Determine their role in synapse targeting and locomotor behavior in postmitotic neurons.

Main Methods:

• Utilized Drosophila melanogaster model system.
• Analyzed the expression patterns of Hunchback and Bicoid in Pair1 neurons.
• Assessed the impact of Hunchback and Bicoid loss-of-function on Pair1 circuit assembly and larval behavior.

Main Results:

• Hunchback and Bicoid are co-expressed in larval Pair1 neurons, with Hunchback activating Bicoid.
• Loss of Hunchback or Bicoid in Pair1 neurons resulted in ectopic presynapses and increased pausing behavior.
• These TFs specifically affected synapse targeting, not neurotransmitter identity or neuronal morphology.

Conclusions:

• Hunchback and Bicoid play cell-autonomous roles in regulating synapse targeting in postmitotic Pair1 neurons.
• This study reveals a novel function for Bicoid beyond embryonic patterning.
• These findings provide insights into how temporal patterning mechanisms drive neural circuit formation and behavior.