Biology subjects

Noblett, N.

Publications and source records attributed to Noblett, N..

3 recordsLinked to original sources

bioRxiv2025

Nuclear hormone receptor regulation of Caudal mediates ventral nerve cord assembly in C. elegans.

The regulatory network governed by CDX/Caudal family transcription factors plays critical roles in shaping embryonic neural development. In C. elegans, we found that proper expression of pal-1, the C. elegans Caudal homologue, is required for correct positioning of motor neuron cell bodies in the first larval stage ventral nerve cord (VNC). We identified an upstream regulatory region within the pal-1 promoter that drives pal-1 expression in a subset of DD and DA neuronal progenitors. We also show that SEX-1, a nuclear hormone receptor, is required for motor neuron positioning in the VNC. Loss of sex-1 results in neuronal positioning defects similar to those observed in pal-1 mutants. This is in part due to a requirement for SEX-1 in promoting pal-1 expression in DD and DA neuronal progenitors during VNC assembly. Double mutant analysis further suggests that sex-1 also has pal-1-independent functions. Together, these findings define a transcriptional hierarchy in which the SEX-1 nuclear hormone receptor regulates the tissue-specific activity of PAL-1 to promote proper motor neuron positioning in the VNC and highlight a conserved role for NHR and CDX/Caudal family proteins in central nerve cord formation. Highlights- PAL-1 is required for proper neuron cell body positioning in the ventral nerve cord (VNC) in newly hatched worms. - An upstream promoter element controls the expression of pal-1 in DD and DA neurons. - The nuclear hormone receptor SEX-1 is required for proper neuron positioning in the VNC. - SEX-1 regulates PAL-1 expression in DD and DA neurons.

developmental biology↗

bioRxiv2024

Dopey-dependent regulation of extracellular vesicles maintains neuronal morphology

Mature neurons maintain their distinctive morphology for extended periods in adult life. Compared to developmental neurite outgrowth, axon guidance, and target selection, relatively little is known of mechanisms that maintain mature neuron morphology. Loss of function in C. elegans DIP-2, a member of the conserved lipid metabolic regulator Dip2 family, results in progressive overgrowth of neurites in adults. We find that dip-2 mutants display specific genetic interactions with sax-2, the C. elegans ortholog of Drosophila Furry and mammalian FRY. Combined loss of DIP-2 and SAX-2 results in severe disruption of neuronal morphology maintenance accompanied by increased release of neuronal extracellular vesicles (EVs). By screening for suppressors of dip-2 sax-2 double mutant defects we identified gain-of-function (gf) mutations in the conserved Dopey family protein PAD-1 and its associated phospholipid flippase TAT-5/ATP9A. In dip-2 sax-2 double mutants carrying either pad-1(gf) or tat-5(gf) mutation, EV release is reduced and neuronal morphology across multiple neuron types is restored to largely normal. PAD-1(gf) acts cell autonomously in neurons. The domain containing pad-1(gf) is essential for PAD-1 function, and PAD-1(gf) protein displays increased association with the plasma membrane and inhibits EV release. Our findings uncover a novel functional network of DIP-2, SAX-2, PAD-1, and TAT-5 that maintains morphology of neurons and other types of cells, shedding light on the mechanistic basis of neurological disorders involving human orthologs of these genes.

neuroscience↗

bioRxiv2024

IPPK-1 and IP6 contribute to ventral nerve cord assembly in C. elegans

Inositol phosphates (IPs) are essential for the development and function of the nervous system. Loss-of-function studies, which demonstrate the importance of specific IP isomers, show their critical role in proper neural tube formation. In this study, we show that inositol pentakisphosphate 2-kinase (IPPK-1), the kinase that phosphorylates IP5 to generate IP6, is involved in assembling the ventral nerve cord (VNC) in C. elegans. We show that mutations in ippk-1 lead to the mispositioning of motor neurons along the VNC of newly hatched larvae. These positioning defects reflect disruption of VNC assembly during embryogenesis, as VNC neuronal progenitors in ippk-1 embryos display a more compact organization after arising on the left and right sides of the embryo, delays in rosette-mediated convergent extension, and defects in cell intercalation. We further show that injection of exogenous IP6 into the gonads of ippk-1 mutants can rescue both embryonic and neuron positioning defects. Our findings indicate that IP isomers, particularly IP6, are important for ventral nerve cord formation in C. elegans. Along with their role in neural tube formation in vertebrates, these results suggests that IP isomers play an ancient role in central nerve cord development. Highlights- ipmk-1 and ippk-1 mutants display neuron position defects in the ventral nerve cord (VNC). - ippk-1 mutants display disorganization in VNC neuronal progenitors during VNC assembly. - IPPK-1 is involved in convergent extension during VNC formation. - Exogenous IP6 rescues larval and embryonic defects in ippk-1 mutants.

developmental biology↗