Neuronal morphology is highly variable, particularly in terms of the complexity of dendritic arborisation, and this variability is crucial for appropriate function. But how is such diversity established and regulated? Wesley Grueber and colleagues (p. ) set out to address the transcriptional inputs into this process using a subset of Drosophila sensory neurons, the multidendritic (md) neurons, whose morphology is regulated by the transcription factor Cut. Cut expression is absent in neurons that have simple morphology and function as proprioceptors, but is expressed at variable levels in nociceptive or touch-sensitive neurons with more complex dendrites. Through a series of mosaic genetic analyses, the authors find that Cut represses the expression of the Pdm1/2 transcription factors in a subset of md neurons, which suppresses the ability of Pdm1/2 to restrain dendritic arborisation. Upstream of Cut, the transcriptional repressors Vestigial and Scalloped modulate Cut levels to limit dendritic elaboration – in this case repressing a complex morphology and favouring a less complex type of branching. Together, these data identify a network of repressive interactions that regulate neuronal morphology and thus help to define neuronal identity and diversity.
