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Biology subjects

Green, R. A.

Publications and source records attributed to Green, R. A..

5 recordsLinked to original sources

A tissue-targeted auxin-inducible degradation toolkit for C. elegans embryogenesis

Many proteins required for embryogenesis are expressed in multiple tissues and across developmental time, often with tissue- and stage-specific roles. To resolve where and when proteins function, we developed a tissue-targeted auxin-inducible degradation toolkit for C. elegans embryogenesis. We generated a plasmid set compatible with single-copy insertion or high-copy extrachromosomal array generation that employs tissue-specific promoters (active in the germline, intestine, muscle, pharynx, neuroblasts, neurons, sensory neurons, epidermis, and pan soma) to drive an operon expressing an optimized auxin-dependent plant F-box factor TIR1 and, in most cases, a fluorescent histone. Using a ubiquitous nuclear envelope marker as a test substrate, we identified single-copy insertions and arrays that exhibit efficient auxin-dependent, tissue-specific target degradation. We also establish a workflow that ensures all functionally important isoforms of a target are tagged and that degradation reproduces the loss-of-function phenotype prior to tissue-specific analysis. Applying the toolkit to the broadly expressed Rho kinase LET-502, we find that degradation in the epidermis, but not in other embryonic tissues, disrupts elongation. Unexpectedly, temporal analysis revealed that LET-502 is required for late as well as early elongation.

developmental biology↗

TMEM209/NPP-28 partitions PLK-1 between the nuclear envelope and nuclear interior during mitosis

The onset of mitosis in animal cells is marked by nuclear envelope breakdown (NEBD), which requires coordinated disassembly of nuclear pore complexes (NPCs) and the nuclear lamina. Polo-like kinase 1 (Plk1/PLK-1) initiates NEBD through phosphorylation of NPC components, but mechanisms that spatially regulate PLK-1 between NPCs and the nuclear interior are unclear. Here, we identify the Caenorhabditis elegans TMEM209 homolog NPP-28 as a transmembrane nucleoporin that concentrates PLK-1 at the nuclear envelope while limiting its nuclear accumulation to promote NEBD. We identify docking sites within NPP-28 that mediate PLK-1 nuclear envelope-association. NPP-28 is phosphorylated by PLK-1 in vitro, and mutational analysis suggests that NPP-28-mediated docking facilitates NEBD, whereas phosphorylation prevents premature NEBD. Simultaneous loss of npp-28 and the transmembrane nucleoporin npp-12/gp210 exacerbates mitotic NEBD defects in early embryos and causes severe defects in germline development. Together, our findings identify NPP-28 as a spatial regulator of PLK-1 during mitosis with functional relationships with other conserved transmembrane nucleoporins depending on context.

cell biology↗

Temporal Interference Stimulation Enhances Neural Regeneration

Neural regeneration therapies aim to treat neurodegeneration by promoting the proliferation and maturation of exogenous or endogenous neural progenitor cells (NPCs). However, their efficacy has been limited. Deep brain stimulation (DBS) via implanted electrodes has been shown to promote neurogenesis. However, its invasiveness precludes deployment in research and widespread clinical use. Temporal interference (TI) has emerged as a strategy for non-invasive, high-precision DBS using multiple kHz-range electric fields, with a frequency difference within the range of neural activity. Here, we validate the potential of TI stimulation for neural regeneration augmentation. We demonstrate that TI stimulation with a theta-band frequency difference enhances the maturation of embryonic neural progenitor cells in vitro. We then demonstrate that theta-band TI stimulation targeting the hippocampus enhances endogenous hippocampal neurogenesis in an in vivo mouse model of Alzheimers disease. By uncovering frequency-specific control of stem cell fate, we propose a clinically relevant regeneration strategy which avoids pharmacological or genetic manipulation. Our results demonstrate focal, non-invasive augmentation of deep-brain neural regeneration. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=197 SRC="FIGDIR/small/670811v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@984165org.highwire.dtl.DTLVardef@1ed8bbdorg.highwire.dtl.DTLVardef@715057org.highwire.dtl.DTLVardef@151882f_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

Hybrid incompatibility emerges at the one-cell stage in interspecies Caenorhabditis embryos

Intrinsic reproductive isolation occurs when genetic divergence between populations disrupts hybrid development, preventing gene flow and enforcing speciation.1-4 Over the past two decades, researchers have identified molecular mechanisms underlying a few dozen cases of hybrid incompatibility in animals.5 Much of this work has focused on mismatches in zygotic gene regulation,6-11 but other mechanisms have also emerged, including symbiont-driven incompatibilities,12 nucleoporin mismatches affecting nuclear-cytoplasmic transport,13 and divergence in centromeric or heterochromatic regions and their regulatory proteins which can lead to the inability of the oocyte cytoplasm to segregate sperm-derived chromosomes.14-19 Since studies to date have focused on a limited number of species, uncovering mechanisms across diverse taxa will be important to understanding broader patterns of hybrid incompatibility. Here, we investigate the mechanistic basis of hybrid incompatibility in Caenorhabditis nematodes by leveraging the ability of C. brenneri females to produce embryos after mating with males from several other species. We find that incompatibilities emerge between fertilization and the onset of zygotic transcription, which begins at the 4-cell stage.20-23 In Caenorhabditis embryos, as in many animals,24,25 sperm deliver chromatin and centrioles into the oocyte.26-29 After remaining quiescent during oocyte meiosis, the sperm chromatin acquires a nuclear envelope, and centrioles initiate centrosome formation.30-32 Centrosomes remain tethered to the sperm pronucleus, which positions them near the cortex to establish anterior-posterior polarity.33,34 We identify two key processes that are destabilized in hybrids: (1) the ability of oocytes to control sperm-derived pronuclear expansion, and (2) successful polar body formation. When sperm pronuclear expansion is delayed, centrosomes detach, which leads to defects in polarity establishment. Hybrid embryos typically experience one or more stochastic failures of early developmental events that accumulate and eventually kill them.

evolutionary biology↗

CYK-4 functions independently of its centralspindlin partner ZEN-4 to cellularize oocytes in germline syncytia

Throughout metazoans, germ cells undergo incomplete cytokinesis to form syncytia connected by intercellular bridges. Formation of gametes ultimately requires bridge closure. Here, we investigate the contribution of the conserved bridge component centralspindlin to oocyte production in C. elegans. Centralspindlin is composed of the Rho family GTPase-activating protein (GAP) CYK-4/MgcRacGAP and the microtubule motor ZEN-4/kinesin-6, which are both essential for cytokinesis. In contrast, we show that oocyte production by the syncytial germline requires CYK-4 but not ZEN-4. Longitudinal imaging after conditional CYK-4 inactivation revealed a role in oocyte cellularization, rather than in generation of syncytial compartments. CYK-4s lipid-binding C1 domain and the GTPase-binding interface of its GAP domain were individually important for oocyte cellularization and for targeting CYK-4 to bridges, where it contributes to enrichment of active RhoA. These results identify a C1-GAP module in CYK-4 that recruits it to bridges in the germline and directs their closure to produce oocytes.\n\nIMPACT STATEMENTThe CYK-4 subunit of centralspindlin, a broadly conserved component of intercellular bridges across metazoa, is required for the cytokinesis-like closure of intercellular bridges that cellularizes oocytes to separate them from germline syncytia.\n\nMAJOR SUBJECT AREASCell Biology, Developmental Biology & Stem Cells

cell biology↗