Biology subjects

Loer, C.

Publications and source records attributed to Loer, C..

3 recordsLinked to original sources

bioRxiv2026

Terminal selector and subtype selector function across 200 million years of nematode evolution

The evolution of brains is subject to investigation in many different animal groups, each offering unique advantages to advance our understanding of the cellular, molecular and regulatory substrates of evolutionary change. Here, we use two nematode species, C. elegans and P. pacificus, separated by more than 200 million years of evolution to explore how neuronal cell types and the regulatory programs instructing the identity of these cell types have evolved over time. Using gene expression pattern analysis, we compare the differentiation programs of over half of all nematode neuron classes. To explore how the gene regulatory architecture of neuronal differentiation programs evolves, we apply our deep understanding of neuronal differentiation programs, controlled by terminal selectors and subtype selectors in C. elegans. Through mutant analysis of orthologous P. pacificus regulatory factors, we elucidate patterns of conservation and novelties over such substantial evolutionary distance. We discovered striking similarities in terminal selector expression and activities throughout the nervous system but also observed that terminal selectors can acquire novel sites of expression and distinct regulatory capabilities, manifested by changes in effector gene expression and, hence, neuronal phenotypes. Our mutant analysis argues for a buffering of terminal selector function and for an evolutionary lability of differences in closely related neuronal subtypes. Taken together, our analysis reveals molecular substrates of evolutionary change in nervous systems.

neuroscience↗

bioRxiv2025

Pervasive homeobox gene function in the male-specific nervous system of Caenorhabditis elegans

We explore here how neuronal cell type diversity is genetically delineated in the context of the large, but poorly studied male-specific nervous system of the nematode Caenorhabditis elegans. Mostly during postembryonic development, the C. elegans male adds 93 male-specific neurons, falling into 25 cardinal classes, to the predominantly embryonically generated, sex-shared nervous system, comprised of 294 neurons (116 cardinal classes). Using engineered reporter alleles, we investigate here the expression pattern of 40 phylogenetically conserved homeodomain proteins within the male-specific nervous system of C. elegans, demonstrating that in aggregate, the expression of these homeodomain proteins covers each individual male-specific neuron. We show that the male-specific nervous system can be subdivided along the anterior/posterior axis in HOX cluster expression domains. The extent of our expression analysis predicts that each individual neuron class is likely defined by unique combinations of homeodomain proteins. Using a collection of newly available molecular markers, we undertake a mutant analysis of five of these genes (unc-30, unc-42, lim-6, lin-11, ttx-1) and identified defects in cell fate specification and/or male copulatory defects in each of these mutant strains. Our analysis expands our understanding of the importance of homeobox genes in nervous system development and function.

neuroscience↗

bioRxiv2024

Episodic rhythmicity is generated by a distributed neural network in the developing mammalian spinal cord

Spinal circuits produce diverse motor outputs that coordinate the rhythm and pattern of locomotor movements. Despite the episodic nature of these behaviours, the neural mechanisms encoding these episodes are not well understood. This study investigated mechanisms producing episodic rhythms evoked by dopamine in isolated neonatal mouse spinal cords. Dopamine-induced rhythms were primarily synchronous and propagated rostro-caudally across spinal segments, with occasional asynchronous episodes. Electrical stimulation of the L5 dorsal root could entrain episodes across segments, indicating afferent control of the rhythm generator and a distributed rostro-caudal network. Episodic activity was observed in isolated thoracic or sacral segments after full spinal transection or bilateral ventrolateral funiculus (VLF) lesions, suggesting a distributed network coupled via VLF projections. Rhythmicity was recorded from axons projecting through the VLF and dorsal roots, but not from cholinergic recurrent excitation via motoneurons or isolated dorsal inhibitory circuits. The data suggest episodic rhythmicity is generated by a flexibly coupled network of spinal interneurons distributed throughout the spinal cord.

neuroscience↗