Dimov, I. M. | Search bioRxiv

bioRxiv2025

The rewiring of a terminal selector regulatory cascade generates convergent neuronal laterality

Neuronal identity is established and maintained by "terminal-selector" transcription factors, yet how these networks evolve remains unclear. We examined the specification of the chemosensory ASE and thermosensory AFD neurons in the nematode Pristionchus pacificus, a species that expresses the terminal-selector, Ppa-CHE-1, in both sensory neurons. To determine if the ASE neurons exhibits left-right laterality, we used HCR-FISH and transgenic reporters to discover 8 ASE left-right-specific and 3 AFD-specific receptor-type guanylyl-cyclases. Late embryos exhibit a multipotential state in which AFD precursors transiently co-express ASEL, ASER and AFD markers. A forward genetic screen for defects in ASER asymmetry identified a Ppa-DIE-1 homolog, whereas the maintenance of AFD neuronal identity requires another terminal-selector, Ppa-TTX-1, and CNG channels, Ppa-TAX-2/TAX-4. Defects in miRNA-processing convert ASEL to ASER fate while mutations in conserved regions in the 3' UTR of the cog-1 homolog reveal multiple miRNA binding sites that toggle between left/right ASE versus AFD identities. Together, these results demonstrate that P. pacificus deploys a convergent, likely miRNA-mediated regulatory repertoire to generate left/right neuronal asymmetry and highlight changes in the Ppa-cog-1 3 UTR as a key locus for rewiring selector networks.

developmental biology↗

bioRxiv2024

Evolution of lateralized gustation in nematodes

Animals with small nervous systems have a limited number of sensory neurons that must encode information from a changing environment. This problem is particularly exacerbated in nematodes that populate a wide variety of distinct ecological niches but only have a few sensory neurons available to encode multiple modalities. How does sensory diversity prevail within this constraint in neuron number? To identify the genetic basis for patterning different nervous systems, we demonstrate that sensory neurons in Pristionchus pacificus respond to various salt sensory cues in a manner that is partially distinct from that of the distantly related nematode Caenorhabditis elegans. By visualizing neuronal activity patterns, we show that contrary to previous expectations based on its genome sequence, the salt responses of P. pacificus are encoded in a left/right asymmetric manner in the bilateral ASE neuron pair. Our study illustrates patterns of evolutionary stability and change in the gustatory system of nematodes. Animals with small nervous systems have evolved left and right asymmetry in their neurons to process various salts at different concentrations.

neuroscience↗