214,848 research outputs found
A single E-box in the <i>Cel-lin-3</i> CRM is not sufficient for <i>lin-3</i> expression in the anchor cell of <i>C</i>. <i>elegans</i>.
No full text(A) New cis-regulatory lin-3 alleles with deleted E-boxL and NHR or NHR and E-boxR. (B) Quantification of vulval induction in these new mutants. Note the complete absence of any induction in the recovered lin-3 alleles (n>30). Scorings of lin-3(1417) animals are the same as those reported in Fig 5 and are used here to indicate that this mutation leads to vulval hypo-induction rather than no induction at all. (C-D) smFISH in lin-3(mf72) (C) and N2 (D) animals. Green spots correspond to lin-3 transcripts and red spots to lag-2 that is used as an anchor cell marker. Blue is DAPI staining of nuclei. Note the absence of lin-3 expression in the anchor cell in the lin-3(mf72) mutant animal. Absence of lin-3 signal in the anchor cell was also confirmed for the other lin-3 alleles.</p
On the sheaf-theoretic SL(2, C) Casson–Lin invariant
No full textWe prove that the (τ-weighted, sheaf-theoretic) SL(2, C) Casson–Lin invariant introduced by Manolescu and the first author is generically independent of the parameter τ and additive under connected sums of knots in integral homology 3-spheres. This addresses two questions asked by Manolescu and the first author. Our arguments involve a mix of topology and algebraic geometry, and rely crucially on the fact that the SL(2, C) Casson–Lin invariant admits an alternative interpretation via the theory of Behrend functions.</p
LIN-1 sumoylation is required for ventral toroid contraction.
No full text(A) Wild-type and K10A, K169A mutant LIN-1::GFP expression in L3 larvae at the Pn.px stage after VPC-specific degradation of AID::SMO-1 from the L2 stage onward. The 1° and 2° VPC descendants are underlined in white. The left panels show the corresponding DIC images overlaid with the LIN-1::GFP signal in green. (B) Quantification of LIN-1::GFP expression levels in 1° and 2° VPC descendants at the Pn.px stage in LIN-1::GFP wild-type and K10A, K169A double mutants under the indicated conditions. See S3 Fig for the corresponding measurements at the Pn.pxx stage. (C) Toroid morphogenesis defects in LIN-1 K10A and K169A single and double mutants at the L4 stage. Left panels show lateral views of z-projections. vulA and vulB1 toroids are outlined by the white rectangle in the top left panel and shown in top (xz) views in the right panels. (D) Quantification of vulA contraction, calculated as the ratio of the vulA and vulB1 toroid diameter. The box plots show the median values with the 25th and 75th percentiles and the whiskers indicate the maximum and minimum values. Where indicated, untreated controls are labelled with–IAA (blue) and animals treated with 1 mM auxin with +IAA (red). In each graph, the numbers of animals scored are indicated by the numbers in brackets. Statistical significance in (B) and (D) was calculated with unpaired two-tailed t-tests. p-values are indicated as * p ≤ 0.05; ** p ≤ 0.01; *** p ≤ 0.001. The scale bars are 10 μm.</p
LIN-39 promotes neuronal fate specification in the Q and V5 lineage.
No full text(A) The expression of lin-39 in AVM, SDQL/R, PDEL/R, and PVDL/R, indicated by the overlapping with neurotransmitter identity markers and specific fate markers (uIs115[mec-17p::TagRFP] for AVM, otIs181[dat-1p::mCh] for PDE, uIs117[lad-2p::mCh] for SDQ). (B) The expression of mab-5 in SDQL. (C) Summary of lin-39 (green) and mab-5 (cyan) expression in the descendants of Q and V5 lineages. (D) The loss of gcy-37 expression in AQR and AVM neurons in lin-39(n1760) mutants and the mispositioning of PQR in mab-5(gk670) mutants; the loss of lad-2 expression in SDQR in lin-39(n1760) mutants, the displacement of SDQL in mab-5(gk670) mutants, and the loss of lad-2 expression in both SDQs in lin-39(n1760) mab-5(e1239) mutants. The right panels show the penetrance for the loss of marker expression and cell body mispositioning. Mean ± SD for the percentage of cells showing corresponding phenotypes from three biological replicates are shown. Double asterisks indicate statistically significant difference (p Chi-square test. (E) The loss of ser-2 expression in PVD and PDE neurons and the loss of F49H12.4 expression in PVD in lin-39(n1760) and ceh-20(u843) mutants. (F) Dopaminergic marker dat-1 is normally expressed in PDE neurons in lin-39 mutants, but PDE shows axonal growth defects. The arrows indicate the termini of PDE axons. The expression of glutamatergic identity marker eat-4 and the PVD terminal selector gene mec-3 in PVD neurons in lin-39 mutants.</p
LIN-2 and FRM-3 are required to maintain locomotory behaviour.
No full text(A) Genomic structure of lin-2 and frm-3 locus, mutant allele characterization, and protein architecture for LIN-2 and FRM-3. The whole promoter region of lin-2a and part of the kinase domain of LIN-2A is deleted in the e1309 mutants. The FERM domain in both frm-3a and frm-3b is deleted in the gk585 mutants. Syb1019 and syb1036 are stop codons in lin-2 and frm-3 that inactivate the expression of lin-2a and lin-2b, and frm-3a and frm-3b. (E, F) Locomotion speed is reduced by the loss of LIN-2 and FRM-3. Representative trajectories of locomotion in wild type (E) and mean locomotion speed in wild type, lin-2(e1309), frm-3(gk585), lin-2(syb1019), frm-3(syb1036), and lin-2(e1309);frm-3(gk585) mutants. To measure locomotion speed, young adult animals were washed with a drop of PBS and then transferred to fresh NGM plates with no bacterial lawn (30 worms per plate). Worm movement recordings (under room temperature 22°C) were started 10 min after the worms were transferred. A 2 min digital video of each plate was captured at 3.75 Hz frame rate by WormLab System (MBF Bioscience). Average speed and tracks were generated for each animal using WormLab software. To confirm the repeatability of the data, the locomotion speed was measured in two independent experiments in two days. For each mutant, around 10–40 animals were analyzed in one experiment. Significance was tested for each experiment. Data are mean ± SEM (**, p p < 0.001 when compared to wild type; n.s., non-significant; one-way ANOVA). The number of worms analyzed for each genotype is indicated in the bar.</p
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<it>lin-12 </it>Notch functions in the adult nervous system of <it>C. elegans</it>
No full textAbstract Background Notch signaling pathways are conserved across species and traditionally have been implicated in cell fate determination during embryonic development. Notch signaling components are also expressed postdevelopmentally in the brains of adult mice and Drosophila. Recent studies suggest that Notch signaling may play a role in the physiological, rather than developmental, regulation of neurons. Here, we investigate a new non-developmental role for Caenorhabditis elegans lin-12 Notch signaling in neurons regulating the spontaneous reversal rate during locomotion. Results The spontaneous reversal rate of C. elegans during normal locomotion is constant. Both lin-12 gain and loss of function mutant animals had significantly increased reversal rates compared to wild type controls. These defects were caused by lin-12 activity, because the loss of function defect could be rescued by a wild type lin-12 transgene. Furthermore, overexpression of lin-12 recapitulated the gain-of-function defect. Increasing or decreasing lin-12 activity in the postdevelopmental adult animal was sufficient to rapidly and reversibly increase reversals, thereby excluding a developmental role for lin-12. Although lin-12 is expressed in the vulval and somatic gonad lineages, we find that these tissues play no role in regulating reversal rates. In contrast, altering lin-12 activity specifically in the nervous system was sufficient to increase reversals. These behavioral changes require components of the canonical lin-12 signaling cascade, including the ligand lag-2 and the transcriptional effector lag-1. Finally, the C. elegans AMPA/kainate glutamate receptor homolog glr-1 shows strong genetic interactions with lin-12, suggesting that glr-1 and/or other glutamate gated channels may be targets of lin-12 regulation. Conclusion Our results demonstrate a neuronal role for lin-12 Notch in C. elegans and suggest that lin-12 acutely regulates neuronal physiology to modulate animal behavior, without altering neuronal cell fate specification or neurite outgrowth. This is consistent with a role for Notch signaling in neurological disease with late onset symptoms.</p
Mammalian LIN-7 PDZ proteins associate with beta-catenin at the cell junctions of epithelia and neurons
No full textThe heterotrimeric PDZ complex containing LIN-2, LIN-7 and LIN-10 is known to be involved in the organization of epithelial and neuronal junctions in Caenorhabditis elegans and mammals. We report here that mammalian LIN-7 PDZ proteins form a complex with cadherin and β-catenin in epithelia and neurons. The association of LIN-7 with cadherin and β-catenin is Ca2+ dependent and is mediated by the direct binding of LIN-7 to the C-terminal PDZ target sequence of β-catenin, as demonstrated by means of co-immunoprecipitation experiments and in vitro binding assays with the recombinant glutathione S-transferase:LIN-7A. The presence of β-catenin at the junction is required in order to relocate LIN-7 from the cytosol to cadherin-mediated adhesions, thus indicating that LIN-7 junctional recruitment is β-catenin dependent and that one functional role of the binding is to localize LIN-7. Moreover, when LIN-7 is present at the β-catenin-containing junctions, it determines the accumulation of binding partners, thus suggesting the mechanism by which β-catenin mediates the organization of the junctional domai
The Cold Shock Domain Protein LIN-28 Controls Developmental Timing in C. elegans and Is Regulated by the lin-4 RNA
No full textAbstractMutations in the heterochronic gene lin-28 of C. elegans cause precocious development where diverse events specific to the second larval stage are skipped. lin-28 encodes a cytoplasmic protein with a cold shock domain and retroviral-type (CCHC) zinc finger motifs, consistent with a role for LIN-28 in posttranscriptional regulation. The 3′UTR of lin-28 contains a conserved element that is complementary to the 22 nt regulatory RNA product of lin-4 and that resembles seven such elements in the 3′UTR of the heterochronic gene lin-14. Both lin-4 activity and the lin-4-complementary element (LCE) are necessary for stage-specific regulation of lin-28. Deleting the LCE produces a dominant gain-of-function allele that causes a retarded phenotype, indicating that lin-28 activity is a switch that controls choices of stage-specific fates
Spiral Structure in Galaxies : A Density Wave Theory
No full textHow does it happen that billions of stars can cooperate to produce the beautiful spirals that characterize so many galaxies, including ours? This book presents a theory of spiral structure that has been developed over the past three decades under the continuous stimulus of new observational studies. The theory unfolds in a way that can be grasped by any reader with an undergraduate science background who is interested in astronomy, as well as by graduate students and scientists actively involved in astronomy or related subjects who want to see the "backbone" and the physical content of the theory. The foundations of this theoretical framework were laid in the early 1960s, following the pioneering work of B. Lindblad. C. C. Lin had already contributed significantly to the field of fluid mechanics when he turned his attention to spiral structures, and he has focused on the problem ever since. Giuseppe Bertin joined this research effort when he first visited at MIT in 1975, bringing to the project knowledge from his work on elliptical galaxies and plasma astrophysics. Together, Bertin and Lin have contributed to the exciting developments on spiral structure of the last few decades, working closely with many observers and other theorists. In this book they describe the density-wave theory with the goal of making the key concepts and astrophysical implications explicit and accessible. The essence of the solution Bertin and Lin present is that the spirals are wave rather than material phenomena and generally trace intrinsic characteristics of the individual galaxies. The book is in three parts—Physical Concepts, Observational Studies, and Dynamical Mechanisms—with most of the technical details confined to the last part
lin-11 in C. elegans uterine morphogenesis
No full textThe Caenorhabditis elegans hermaphrodite egg-laying system comprises several tissues, including the uterus and vulva. lin-11 encodes a LIM domain transcription factor needed for certain vulval precursor cells to divide asymmetrically. Based on lin-11 expression studies and the lin-11 mutant phenotype, we find that lin-11 is also required for C. elegans uterine morphogenesis. Specifically, lin-11 is expressed in the ventral uterine intermediate precursor π cells and their progeny (the utse and uv1 cells), which connect the uterus to the vulva. Like π cell induction, the uterine lin-11 expression responds to the uterine anchor cell and the lin-12-encoded receptor. In wild type animals, the utse, which forms the planar process at the uterinevulval interface, fuses with the anchor cell. We found that, in lin-11 mutants, utse differentiation was abnormal, the utse failed to fuse with the anchor cell and a functional uterine-vulval connection was not made. These findings indicate that lin-11 is essential for uterine-vulval morphogenesis
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