Biology subjects

Nance, J.

Publications and source records attributed to Nance, J..

8 recordsLinked to original sources

bioRxiv2026

RAB-35 regulates distinct steps of trogocytosis in the biting and bitten cell

Trogocytosis is a form of cellular cannibalism in which a cell "bites" off pieces of another cell. Here, we investigate the molecular mechanisms of a developmentally programmed C. elegans trogocytic event that occurs when endodermal cells bite off and digest pieces of primordial germ cells (PGCs) called lobes. Through a genetic screen, we identify the Rab family small GTPase rab-35 as a central regulator of trogocytosis and show that its function is required in both biting (endodermal) and bitten (PGC) cells. Within endodermal cells, RAB-35 enriches around trogocytosed PGC lobes, promotes the removal of phosphatidylinositol 4,5-bisphosphate (PIP2), and is required for lobe digestion. By contrast, we show that RAB-35 within PGCs works with the ESCRT complex to promote scission of the PGC lobe from the cell body. Our findings identify a new regulator of trogocytosis that has distinct functions in the biting and bitten cells and provide evidence that the bitten cell contributes to the scission of its own membrane.

cell biology↗

bioRxiv2025

Integrin promotes basement membrane crossing and branching of an invading intracellular tube

The narrowest biological tubes are comprised of cells that hollow to form an intracellular lumen. Here, we examine early lumenogenesis of the C. elegans excretory cell, which branches to form an H-shaped intracellular tube spanning the length of the worm. Using genetically paralyzed embryos to freeze movement, we describe lumen initiation and branching for the first time using time-lapse fluorescence microscopy. We show that the excretory cell lumen forms through a plasma membrane invasion mechanism when a nascent lumen grows from the plasma membrane into the cytoplasm. The lumen subsequently extends along the left-right axis before branching to form anterior-posterior projections. Through a genetic screen, we identify mutations in ina-1/-integrin and pat-3/{beta}-integrin that block lumenogenesis at the anterior-posterior branching step, and we show that integrin function is required within the excretory cell. Finally, we find that the excretory cell crosses the epidermal basement membrane where anterior-posterior branches form and demonstrate that basement membrane crossing fails in integrin mutant embryos. Our findings reveal how an intracellular lumen initiates and branches and identify integrins and basement membrane as key branching regulators.

developmental biology↗

bioRxiv2023

C. elegans Afadin is required for epidermal morphogenesis and functionally interfaces with the cadherin-catenin complex and RhoGAP PAC-1/ARHGAP21

During epithelial morphogenesis, the apical junctions connecting cells must remodel as cells change shape and make new connections with their neighbors. In the C. elegans embryo, new apical junctions form when epidermal cells migrate and seal with one another to encase the embryo in skin ( ventral enclosure), and junctions remodel when epidermal cells change shape to squeeze the embryo into a worm shape ( elongation). The junctional cadherin-catenin complex (CCC), which links epithelial cells to each other and to cortical actomyosin, is essential for C. elegans epidermal morphogenesis. RNAi genetic enhancement screens have identified several proteins that interact with the CCC to promote epidermal morphogenesis, including the scaffolding protein Afadin (AFD-1), whose depletion alone results in only minor morphogenesis defects. Here, by creating a null mutation in afd-1, we show that afd-1 provides a significant contribution to ventral enclosure and elongation on its own. Unexpectedly, we find that afd-1 mutant phenotypes are strongly modified by diet, revealing a previously unappreciated maternal nutritional input to morphogenesis. We identify functional interactions between AFD-1 and the CCC by demonstrating that E-cadherin is required for the polarized distribution of AFD-1 to cell contact sites in early embryos. Finally, we show that afd-1 promotes the enrichment of polarity regulator and CCC-interacting protein PAC-1/ARHGAP21 to cell contact sites, and identify genetic interactions suggesting that afd-1 and pac-1 regulate epidermal morphogenesis at least in part through parallel mechanisms. Our findings reveal that C. elegans AFD-1 makes a significant contribution to epidermal morphogenesis and functionally interfaces with core and associated CCC proteins.

developmental biology↗

bioRxiv2023

ZIF-1-mediated degradation of endogenous and heterologous zinc finger proteins in the C. elegans germ line

Rapid and conditional protein depletion is the gold standard genetic tool for deciphering the molecular basis of developmental processes. Previously, we showed that by conditionally expressing the E3 ligase substrate adaptor ZIF-1 in Caenorhabditis elegans somatic cells, proteins tagged with the first CCCH Zn finger (ZF1) domain from the germline regulator PIE-1 degrade rapidly, resulting in loss-of-function phenotypes. The described role of ZIF-1 is to clear PIE-1 and several other CCCH Zn finger proteins from early somatic cells, helping to enrich them in germline precursor cells. Here, we show that proteins tagged with the PIE-1 ZF1 domain are subsequently cleared from primordial germ cells in embryos and from undifferentiated germ cells in larvae and adults by ZIF-1. We harness germline ZIF-1 activity to degrade a ZF1-tagged heterologous protein from PGCs and show that its depletion produces phenotypes equivalent to those of a null mutation. Our findings reveal that ZIF-1 switches roles from degrading CCCH Zn finger proteins in somatic cells to clearing them from undifferentiated germ cells, and that ZIF-1 activity can be harnessed as a new genetic tool to study the early germ line.

cell biology↗

bioRxiv2023

Germline TFAM levels regulate mitochondrial DNA copy number and mutant heteroplasmy in C. elegans

The mitochondrial genome (mtDNA) is packaged into discrete protein-DNA complexes called nucleoids. mtDNA packaging factor TFAM (mitochondrial transcription factor-A) promotes nucleoid compaction and is required for mtDNA replication. Here, we investigate how changing TFAM levels affects mtDNA in the Caenorhabditis elegans germ line. We show that increasing germline TFAM activity boosts mtDNA number and significantly increases the relative proportion of a selfish mtDNA mutant, uaDf5. We conclude that TFAM levels must be tightly controlled to ensure appropriate mtDNA composition in the germ line.

cell biology↗

bioRxiv2022

Independent regulation of mtDNA quantity and quality resets the mitochondrial genome in C. elegans primordial germ cells

Mitochondria contain an independent genome, called mtDNA, which contains essential metabolic genes. Although mtDNA mutations occur at high frequency, they are inherited infrequently, indicating that germline mechanisms limit their accumulation. To determine how germline mtDNA is regulated, we examined the control of mtDNA quantity and quality in C. elegans primordial germ cells (PGCs). We show that PGCs generate a bottleneck in mtDNA number by segregating mitochondria into lobe-like protrusions that are cannibalized by adjacent cells, reducing mtDNA content two-fold. As PGCs exit quiescence and divide, mtDNAs replicate to maintain a set point of [~]200 mtDNAs per germline stem cell. Whereas PGC lobe cannibalism eliminates mtDNAs stochastically, we show that the kinase PINK1, operating independently of Parkin and autophagy, preferentially reduces the fraction of mutant mtDNAs. Thus, PGCs employ parallel mechanisms to control both the quantity and quality of the founding population of germline mtDNAs.

cell biology↗

bioRxiv2020

A polarity pathway for exocyst-dependent intracellular tube extension

Lumen extension in intracellular tubes can occur by the directed fusion of vesicles with an invading apical membrane domain. Within the C. elegans excretory cell, which contains an intracellular tube, the exocyst vesicle-tethering complex is enriched at the lumenal membrane domain and is required for tube formation, suggesting that it targets vesicles needed for lumen extension. Here, we identify a polarity pathway that promotes intracellular tube formation by enriching the exocyst at the lumenal membrane. We show that the PAR polarity proteins PAR-6 and PKC-3/aPKC localize to the lumenal membrane domain and function within the excretory cell to promote lumen extension, similar to exocyst component SEC-5 and exocyst regulator RAL-1. Using acute protein depletion, we find that PAR-6 is required to recruit the exocyst to the lumenal membrane domain, whereas PAR-3, which functions as an exocyst receptor in mammalian cells, appears to be dispensable for exocyst localization and lumen extension. Finally, we show that the Rho GTPase CDC-42 and the RhoGEF EXC-5/FGD act as upstream regulators of lumen formation by recruiting PAR-6 and PKC-3 to the lumenal membrane. Our findings reveal a molecular pathway that connects Rho GTPase signaling, cell polarity, and vesicle-tethering proteins to promote lumen extension in intracellular tubes.

cell biology↗

bioRxiv2019

Genomic landscape of 261 childhood cancer patient-derived xenograft models

Accelerating cures for children with cancer remains an immediate challenge due to extensive oncogenic heterogeneity between and within histologies, distinct molecular mechanisms evolving between diagnosis and relapsed disease, and limited therapeutic options. To systematically prioritize and rationally test novel agents in preclinical murine models, researchers within the Pediatric Preclinical Testing Consortium are continuously developing patient-derived xenografts (PDXs) from high-risk childhood cancers, many refractory to current standard-of-care treatments. Here, we genomically characterize 261 PDX models from 29 unique pediatric cancer malignancies and demonstrate faithful recapitulation of histologies, subtypes, and refine our understanding of relapsed disease. Expression and mutational signatures are used to classify tumors for TP53 and NF1 inactivation, as well as impaired DNA repair. We anticipate that these data will serve as a resource for pediatric oncology drug development and guide rational clinical trial design for children with cancer.\n\nHighlightsO_LIMultiplatform genomic analysis defines landscape of 261 pediatric cancer patient derived xenograft (PDX) models\nC_LIO_LIPediatric patient derived xenografts faithfully recapitulate relapsed disease\nC_LIO_LIInferred TP53 pathway inactivation correlates with pediatric cancer copy number burden\nC_LIO_LISomatic mutational signatures predict impaired DNA repair across multiple histologies\nC_LI

genomics↗