A panoramic view of the expression and function of the Doublesex/DMRT gene family in C. elegans

Throughout the animal kingdom, sex determination and sexual differentiation are orchestrated by a strikingly diverse set of regulatory factors. The only type of molecules consistently deployed during sexual differentiation are members of the Doublesex/MAB-3-related transcription factor (DMRT) family. Although each animal genome codes for a multitude of DMRT family members, in no species has the full array of DMRT genes been comprehensively analyzed across the entire animal, in all sexes and throughout development. Hence, the extent of deployment of DMRT genes in sexual differentiation remains unknown. We describe here a genome- and nervous system-wide expression and functional analysis of all members of the DMRT gene family. Leveraging genome-engineered reporter alleles of all 10 DMRT genes of the nematode Caenorhabditis elegans, we find that 6 DMRTs display sexually dimorphic expression in somatic and/or reproductive tissues, including in cell and tissue types not previously known to be sexually dimorphic. In the nervous system, DMRT protein expression covers many, although not all, known sexually dimorphic neuron types. Analyses of DMRT null mutant alleles reveal a suite of neuronal differentiation defects, ranging from altered neurotransmitter identities and switched neuropeptide signatures to impaired glia-to-neuron transdifferentiation. Several DMRT proteins do not exhibit sexually dimorphic expression, indicating roles beyond sexual differentiation. Similar comprehensive analyses of DMRT genes in other organisms may help to better understand the extent and regulation of sex-specific cellular differentiation programs.