The C. elegans DAF-19M module: a shift from general ciliogenesis to ciliary and behavioral specialization

Abstract

In animals, cilia are important for the interaction with environments and the proper function of tissues and organs. Understanding the distinctive identities of each type of ciliated cell is essential for therapeutic solutions for ciliopathies, complex disorders with impairments of various organs caused by defective cilia development and function. Here, we report a regulatory module consisting of a cascade of transcription factors and their target genes that confer the cell type-specific ciliary identities on the IL2 ciliated neurons in C. elegans. We found that DAF-19M, isoform of the sole C. elegans RFX transcription factor DAF-19, through X-box promoter motif variants, heads a regulatory module in IL2 neurons, comprising the core target genes klp-6 (kinesin), osm-9 (TRP channel), and cwp-4 (novel); under the overall control of terminal selector proteins UNC-86 and CFI-1. Considering the conservation of this DAF-19M module in IL2 neurons for nictation, a dauer larva-specific behavior, and in male-specific neurons for mating behavior, we propose the existence of an evolutionarily adaptable, hard-wired genetic module for distinct behaviors that share the feature "recognizing the environment."