The C. elegans Zonula Occludens Ortholog Cooperates with the Cadherin Complex to Recruit Actin during Morphogenesis

SummaryThe dramatic cell-shape changes necessary to form a multicellular organism require cell-cell junctions to be both pliable and strong. The zonula occludens (ZO) subfamily of membrane-associated guanylate kinases (MAGUKs) are scaffolding molecules thought to regulate cell-cell adhesion [1–3], but there is little known about their roles in vivo. To elucidate the functional role of ZO proteins in a living embryo, we have characterized the sole C. elegans ZO family member, ZOO-1. ZOO-1 localizes with the cadherin-catenin complex during development, and its junctional recruitment requires the transmembrane proteins HMR-1/E-cadherin and VAB-9/claudin, but surprisingly, not HMP-1/α-catenin or HMP-2/β-catenin. zoo-1 knockdown results in lethality during elongation, resulting in the rupture of epidermal cell-cell junctions under stress and failure of epidermal sheet sealing at the ventral midline. Consistent with a role in recruiting actin to the junction in parallel to the cadherin-catenin complex, zoo-1 loss of function reduces the dynamic recruitment of actin to junctions and enhances the severity of actin filament defects in hypomorphic alleles of hmp-1 and hmp-2. These results show that ZOO-1 cooperates with the cadherin-catenin complex to dynamically regulate strong junctional anchorage to the actin cytoskeleton during morphogenesis

Polarized Rac-dependent protrusions drive epithelial intercalation in the embryonic epidermis of C. elegans

Cell intercalation is a fundamental, coordinated cell rearrangement process that shapes tissues throughout animal development. Studies of intercalation within epithelia have focused almost exclusively on the localized constriction of specific apical junctions. Another widely deployed yet poorly understood alternative mechanism of epithelial intercalation relies on basolateral protrusive activity. Using the dorsal embryonic epidermis of Caenorhabditis elegans, we have investigated this alternative mechanism using high-resolution live cell microscopy and genetic analysis. We find that as dorsal epidermal cells migrate past one another they produce F-actin-rich protrusions polarized at their extending (medial) edges. These protrusions are controlled by the C. elegans Rac and RhoG orthologs CED-10 and MIG-2, which function redundantly to polarize actin polymerization upstream of the WAVE complex and WASP, respectively. We also identify UNC-73, the C. elegans ortholog of Trio, as a guanine nucleotide exchange factor (GEF) upstream of both CED-10 and MIG-2. Further, we identify a novel polarizing cue, CRML-1, which is the ortholog of human capping Arp2/3 myosin I linker (CARMIL), that localizes to the nonprotrusive lateral edges of dorsal cells. CRML-1 genetically suppresses UNC-73 function and, indirectly, actin polymerization. This network identifies a novel, molecularly conserved cassette that regulates epithelial intercalation via basolateral protrusive activity

\u3ci\u3emig-5/Dsh\u3c/i\u3e Controls Cell Fate Determination and Cell Migration in \u3ci\u3eC. elegans\u3c/i\u3e

Cell fate determination and cell migration are two essential events in the development of an organism. We identify mig-5, a Dishevelled family member, as a gene that regulates several cell fate decisions and cell migrations that are important during C. elegans embryonic and larval development. In offspring from mig-5 mutants, cell migrations are defective during hypodermal morphogenesis, QL neuroblast migration, and the gonad arm migration led by the distal tip cells (DTCs). In addition to abnormal migration, DTC fate is affected, resulting in either an absent or an extra DTC. The cell fates of the anchor cell in hermaphrodites and the linker cells in the male gonad are also defective, often resulting in the cells adopting the fates of their sister lineage. Moreover, 2° vulval precursor cells occasionally adopt the 3° vulval cell fate, resulting in a deformed vulva, and the P12 hypodermal precursor often differentiates into a second P11 cell. These defects demonstrate that MIG-5 is essential in determining proper cell fate and cell migration throughout C. elegans development

Exploring the Impact of Efficacy Messages on Cessation-Related Outcomes Using Ecological Momentary Assessment

Introduction:Observational studies indicate that cigarette package inserts with efficacy messages about the benefits of quitting (i.e. response efficacy) and recommendations for successful cessation increase smokers’ self-efficacy to quit and promote sustained cessation. However, the effects of inserts with such efficacy messages have not been studied using experimental designs. This study used ecological momentary assessment (EMA) to assess smokers’ responses to efficacy inserts.Material and Methods:In a randomized case-crossover study among smokers from the United States (n=23), participants received a one-week supply of cigarettes with efficacy inserts and a one-week supply without any inserts, and were randomized to use the packs with inserts on either the first or second week of the study. For 14 consecutive days, participants used a smartphone to answer brief surveys on cessation-related variables during smoking sessions and at the beginning of each day. Multilevel mixed-effects linear and logistic regression models compared responses during the insert period to those of the non-insert period.Results:The insert period was associated with greater desire to quit (b=0.21, p=0.012), motivation to quit (b=0.18, p=0.001), self-efficacy to cut down (b=0.26, p\u3c0.001) and to quit (b=0.28, p\u3c0.000), and response efficacy/ perceived benefits of quitting (b=0.13, p=0.012). Insert exposure was not significantly associated with forgoing cigarettes (OR=1.9, p=0.2).Conclusions:Results from this EMA study suggest that inserts with efficacy messages may promote determinants of smoking cessation. This is consistent with observational research in Canada, which is the only country to use inserts with efficacy messages as well as pictorial warnings about smoking risks on the outside of packs. Future studies should assess the extent to which efficacy inserts can not only be used to communicate health information to smokers but also work in synergy with pictorial warnings

The N- or C-terminal domains of DSH-2 can activate the C. elegans Wnt/β-catenin asymmetry pathway

AbstractDishevelleds are modular proteins that lie at the crossroads of divergent Wnt signaling pathways. The DIX domain of dishevelleds modulates a β-catenin destruction complex, and thereby mediates cell fate decisions through differential activation of Tcf transcription factors. The DEP domain of dishevelleds mediates planar polarity of cells within a sheet through regulation of actin modulators. In Caenorhabditis elegans asymmetric cell fate decisions are regulated by asymmetric localization of signaling components in a pathway termed the Wnt/β-catenin asymmetry pathway. Which domain(s) of Disheveled regulate this pathway is unknown. We show that C. elegans embryos from dsh-2(or302) mutant mothers fail to successfully undergo morphogenesis, but transgenes containing either the DIX or the DEP domain of DSH-2 are sufficient to rescue the mutant phenotype. Embryos lacking zygotic function of SYS-1/β-catenin, WRM-1/β-catenin, or POP-1/Tcf show defects similar to dsh-2 mutants, including a loss of asymmetry in some cell fate decisions. Removal of two dishevelleds (dsh-2 and mig-5) leads to a global loss of POP-1 asymmetry, which can be rescued by addition of transgenes containing either the DIX or DEP domain of DSH-2. These results indicate that either the DIX or DEP domain of DSH-2 is capable of activating the Wnt/β-catenin asymmetry pathway and regulating anterior–posterior fate decisions required for proper morphogenesis

Wnt/Frizzled Signaling Controls C. elegans Gastrulation by Activating Actomyosin Contractility

Embryonic patterning mechanisms regulate the cytoskeletal machinery that drives morphogenesis, but there are few cases where links between patterning mechanisms and morphogenesis are well understood. We have used a combination of genetics, in vivo imaging, and cell manipulations to identify such links in C. elegans gastrulation. Gastrulation in C. elegans begins with the internalization of endodermal precursor cells in a process that depends on apical constriction of ingressing cells

TES-1/Tes and ZYX-1/Zyxin protect junctional actin networks under tension during epidermal morphogenesis in the C. elegans embryo

Acknowledgments cDNA clones for hmr-1, ajm-1, zyx-1, zoo-1, hmp-1, and tes-1 (yk collection) were provided by Yuji Kohara (National Institute of Genetics). A.M.L., Y.Z., B.G.L., S.C.T.M., and J.H. were supported by NIH grant R01GM058038 and NIH MIRA R35GM145312 awarded to J.H.; S.C.T.M. was supported by a Gilliam Fellowship from the Howard Hughes Medical Institute and by an Advanced Opportunities Fellowship and a COVID-19 dissertation completion fellowship from the University of Wisconsin-Madison; S.B. and A.A. were supported by NIH MIRA R35GM134865 awarded to A.A.; J.D.W. was supported by NIH grant F32GM122372 and by NIH grant R01GM104032 and the Army Research Office Multidisciplinary University Research Initiative W911NF1410403 awarded to M.L.G.; and B.G. and M.M.S. were supported by NIH MIRA R35GM134838 awarded to B.G. and NIH grant F32GM119348 awarded to M.M.S. Some strains were provided by the Caenorhabditis Genetics Center (CGC; https://cbs.umn.edu/cgc/home), which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440).Peer reviewedPostprin

Odradek and the rethinking of political method in the work of art

While creating a large-scale transparency from a story by Kafka, Odradek, Táboritská 8, Prague, 18 July 1994, the artist Jeff Wall in his text ‘Gestus’ (1984) draws on Brecht's concept of gestus, which was concerned with freezing the action into a tableau vivant in order to cause the audience to reflect on the characters' and their own positions in economic and social relations. I propose to complicate this by considering the discussions between Benjamin, Brecht and Adorno around Kafka. In ‘Notes on Kafka’ (1953), Adorno writes, ‘The zone in which it is impossible to die is also the no-man’s-land between man and thing: within it meet Odradek.’ (Prisms). Adorno also remarks in that essay, ‘what would truly be history…has not yet begun’ (p.257). If Odradek is seen as outmoded, then it might also be thought of in relation to Benjamin’s conception of the Surrealist object. In the discussions Benjamin had with Brecht in the summer of 1934, Brecht was critical of Kafka’s ‘mystification’, and said that ‘Kafka’s outlook is that of a man caught under the wheels. Odradek is characteristic of this outlook…’ Benjamin makes what Brecht calls this ‘mystification’ into a positive quality of Kafka’s stories, which have the form of parables, but without the law or doctrine that would allow their decipherment. According to Hamacher gesture for Benjamin occupies a ‘cloudy spot’ of opacity and impossibility’. In Kafka, according to Benjamin, there is Umkehr, glossed by Weber as ‘“inversion,” reversal, or also, turnabout’. To work instrumentally towards the opening that Kafka gestures towards, would be to reinstitute precisely the continuum it interrupts. Odradek is the site of a displacement between different conceptions of art at a point where history hangs in the balance

Genome-wide Association Study of Susceptibility to Particulate Matter–Associated QT Prolongation

BACKGROUND: Ambient particulate matter (PM) air pollution exposure has been associated with increases in QT interval duration (QT). However, innate susceptibility to PM-associated QT prolongation has not been characterized. OBJECTIVE: To characterize genetic susceptibility to PM-associated QT prolongation in a multi-racial/ethnic, genome-wide association study (GWAS). METHODS: Using repeated electrocardiograms (1986–2004), longitudinal data on PM<10 μm in diameter (PM10), and generalized estimating equations methods adapted for low-prevalence exposure, we estimated approximately 2.5×106 SNP×PM10 interactions among nine Women’s Health Initiative clinical trials and Atherosclerosis Risk in Communities Study subpopulations (n=22,158), then combined subpopulation-specific results in a fixed-effects, inverse variance-weighted meta-analysis. RESULTS: A common variant (rs1619661; coded allele: T) significantly modified the QT-PM10 association (p=2.11×10−8). At PM10 concentrations >90th percentile, QT increased 7 ms across the CC and TT genotypes: 397 (95% confidence interval: 396, 399) to 404 (403, 404) ms. However, QT changed minimally across rs1619661 genotypes at lower PM10 concentrations. The rs1619661 variant is on chromosome 10, 132 kilobase (kb) downstream from CXCL12, which encodes a chemokine, stromal cell-derived factor 1, that is expressed in cardiomyocytes and decreases calcium influx across the L-type Ca2+ channel. CONCLUSIONS: The findings suggest that biologically plausible genetic factors may alter susceptibility to PM10-associated QT prolongation in populations protected by the U.S. Environmental Protection Agency’s National Ambient Air Quality Standards. Independent replication and functional characterization are necessary to validate our findings. https://doi.org/10.1289/EHP34