Hox Function Is Required for the Development and Maintenance of the Drosophila Feeding Motor Unit

• Hox gene Dfd is critical for feeding motor patterns in Drosophila
• Dfd instructs motor unit formation via stage- and tissue-specific target genes
• Synaptic specificity is dependent on actions of Dfd in motor neurons and muscles
• Maintenance of synapses is directly regulated by Dfd

SummaryFeeding is an evolutionarily conserved and integral behavior that depends on the rhythmic activity of feeding muscles stimulated by specific motoneurons. However, critical molecular determinants underlying the development of the neuromuscular feeding unit are largely unknown. Here, we identify the Hox transcription factor Deformed (Dfd) as essential for feeding unit formation, from initial specification to the establishment of active synapses, by controlling stage-specific sets of target genes. Importantly, we found Dfd to control the expression of functional components of synapses, such as Ankyrin2-XL, a protein known to be critical for synaptic stability and connectivity. Furthermore, we uncovered Dfd as a potential regulator of synaptic specificity, as it represses expression of the synaptic cell adhesion molecule Connectin (Con). These results demonstrate that Dfd is critical for the establishment and maintenance of the neuromuscular unit required for feeding behavior, which might be shared by other group 4 Hox genes.

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