The BED finger domain protein MIG-39 halts migration of distal tip cells in Caenorhabditis elegans

AbstractOrgans are often formed by the extension and branching of epithelial tubes. An appropriate termination of epithelial tube extension is important for generating organs of the proper size and morphology. However, the mechanism by which epithelial tubes terminate their extension is mostly unknown. Here we show that the BED-finger domain protein MIG-39 acts to stop epithelial tube extension in Caenorhabditis elegans. The gonadal leader cells, called distal tip cells (DTCs), migrate in a U-shaped pattern during larval development and stop migrating at the young adult stage, generating a gonad with anterior and posterior U-shaped arms. In mig-39 mutants, however, DTCs overshot their normal stopping position. MIG-39 promoted the deceleration of DTCs, leading to the proper timing and positioning of the cessation of DTC migration. Among three Rac GTPase genes, mutations in ced-10 and rac-2 enhanced the overshoot of anterior DTCs, while they suppressed that of posterior DTCs of mig-39 mutants. On the other hand, the mutation in mig-2 suppressed both the anterior and posterior DTC defects of mig-39. Genetic analyses suggested that MIG-39 acts in parallel with Rac GTPases in stopping DTC migration. We propose a model in which the anterior and posterior DTCs respond in an opposite manner to the levels of Rac activities in the cessation of DTC migration

Accuracy of wind observations from open-ocean buoys: Correction for flow distortion

The comparison of equivalent neutral winds obtained from (a) four WHOI buoys in the subtropics and (b) scatterometer estimates at those locations reveals a root-mean-square (RMS) difference of 0.56-0.76 m/s. To investigate this RMS difference, different buoy wind error sources were examined. These buoys are particularly well suited to examine two important sources of buoy wind errors because: (1) redundant anemometers and a comparison with numerical flow simulations allow us to quantitatively assess flow distortion errors, and (2) one-minute sampling at the buoys allows us to examine the sensitivity of buoy temporal sampling/averaging in the buoy-scatterometer comparisons. The inter-anemometer difference varies as a function of wind direction relative to the buoy wind vane and is consistent with the effects of flow distortion expected based on numerical flow simulations. Comparison between the anemometers and scatterometer winds supports the interpretation that the inter-anemometer disagreement, which can be up to 5% of the wind speed, is due to flow distortion. These insights motivate an empirical correction to the individual anemometer records and subsequent comparison with scatterometer estimates show good agreement

Depletion of <i>gon-1</i> causes INS-18 secretion defects.

<p>(a, b) Fluorescent images of INS-18::Venus, and (inset) DIC images in the head neurons of a wild-type animal (a), a <i>gon-1(tm3146)</i> mutant animal (b) (300 msec. exposure time). The scale bar indicates 10 μm. (c) Quantification of fluorescence in neurons. The graph represents the combined results of 3 independent experiments (n > 20 neurons per strain). *p < 0.05. Bars represent the mean ± SE. Representative fluorescent images of INS-18::Venus in the coelomocytes of a wild-type animal (d) and a <i>gon-1(tm3146)</i> mutant animal (e) (3 sec. exposure time). Coelomocytes are outlined with dotted circles in the fluorescent images. The scale bar indicates 10 μm. (f) Quantification of fluorescence in coelomocytes. The graph represents the combined results of 3 independent experiments (n > 20 coelomocytes per strain). Fluorescence intensity was examined using ImageJ (NIH, Bethesda, MD). ***p < 0.005. Bars represent the mean ± SE.</p

<i>gon-1</i> is expressed in a subset of neurons.

<p>(a, c), GFP fluorescence; (b, d), DIC image. (a) GFP is observed in some head neurons (arrowheads), intestine, and excretory cells in the larva. (c) GFP is observed in a CAN neuron (arrowhead), an excretory canal cell, and body wall muscle cells.</p

Depletion of <i>gon-1</i> causes DAF-7 secretion defects.

<p>(a, b) Fluorescent images of DAF-7::mCherry, and DIC images (inset) in the head neurons of a wild-type animal (a) and a <i>gon-1(tm3146)</i> mutant animal (b) (160 msec. exposure time). The scale bar indicates 10 μm. (c) Quantification of the mCherry fluorescence in neurons. The graph represents the combined results of 3 independent experiments (n > 20 neurons per strain). *p < 0.05. Bars represent the mean ± SE. (d, e) Representative fluorescent images of DAF-7::mCherry in the coelomocytes of wild-type (d) and a <i>gon-1(tm3146)</i> mutant (e) animals (100 msec. exposure time). Coelomocytes are outlined with dotted circles in the fluorescent images. Insets show DIC images. The scale bar indicates 10 μm. (f) Quantification of the mCherry fluorescence in coelomocytes. The graph represents the combined results of 3 independent experiments (n > 30 coelomocytes per strain). Fluorescence intensity was examined using ImageJ (NIH, Bethesda, MD). *p < 0.05. Bars represent the mean ± SE.</p

GON-1 acts for insulin signaling at peripheral tissues.

<p>Representative images of DAF-16a::GFP localization (a, c, e, g, i, k, m, o) and DIC (b, d, f, h, j, l, n, p) in wild-type (a, b), <i>gon-1(tm3146)</i> (c, d), <i>gon-1(tm3146); tmEx[gon-1p</i>::<i>gon-1(sig_GON)]</i> (e, f), <i>gon-1(tm3146); tmEx[unc-119p</i>::<i>gon-1(sig_GON)]</i> (g, h), <i>gon-1(tm3146); tmEx[myo-3p</i>::<i>gon-1(sig_GON)]</i> (i, j) and <i>gon-1(tm3146); tmEx[myo-3p</i>::<i>gon-1(sig_GON)</i>, <i>unc-119p</i>::<i>gon-1(sig_GON)]</i> (k, l) animals at the L2 stage. Arrowheads indicate nuclei of body wall muscle cells. Arrows indicate nuclei of other cells including intestinal cells. The scale bar indicates 20 μm for a-l. The white boxes marked in (i—l) are enlarged in (m—p). The scale bar indicates 5 μm.</p

Depletion of <i>gon-1</i> causes INS-7 secretion defects.

<p>Representative fluorescent images of INS-7::mCherry (a, c, e, g) (500 msec. exposure time), <i>unc-119p</i>::<i>GFP</i> (b, d, f, h) and DIC images (inset) in <i>ins-7</i> expressing neurons. (a, b) Wild-type. (c, d) <i>gon-1(tm3146)</i>. The accumulation of INS-7::mCherry was observed in some neurons in the <i>gon-1(tm3146)</i> mutant background. (e, f) <i>gon-1(tm3146); tmEx[gon-1p</i>::<i>gon-1(sig_GON)]</i> animals. (g, h) <i>gon-1(tm3146); tmEx[unc-119p</i>::<i>gon-1(sig_GON)]</i> animals. The accumulation of INS-7::mCherry was scarcely observed in <i>gon-1(tm3146); tmEx[gon-1p</i>::<i>gon-1(sig_GON)]</i> and <i>gon-1(tm3146); tmEx[unc-119p</i>::<i>gon-1(sig_GON)]</i> animals. (i) Quantification of the fluorescence in neurons. The graph represents the combined results of 4 independent experiments (n > 20 neurons per strain). *p < 0.05. **p < 0.01. Bars represent the mean ± SE. Representative fluorescent images of INS-7::mCherry (j, k) and DIC images (inset) of the coelomocytes of wild-type (j) and <i>gon-1(tm3146)</i> mutant (k) animals (100 msec. exposure time). Coelomocytes are outlined with dotted circles in the fluorescent images. (l) Quantification of the fluorescence in coelomocytes. The graph represents the combined results of 4 independent experiments (n > 30 coelomocytes per strain). Fluorescence intensity was examined using ImageJ (NIH, Bethesda, MD). *p < 0.05. Bars represent the mean ± SE.</p

GON-1 and DAF-28 are expressed in the same cells.

<p>(a, b) Representative fluorescent images of a <i>gon-1(tm3146)</i> mutant animal co-expressing <i>gon-1p</i>::<i>GFP</i> (a) and <i>daf-28p</i>::<i>daf-28</i>::<i>mCherry</i> (b). (c) The merged image. (d) The DIC image of the same field shown in (a-c). The scale bar indicates 5 μm. (e, f) Representative fluorescent images of <i>gon-1p</i>::<i>mCherry</i> (e) and <i>mgIs40[daf-28p</i>::<i>GFP]</i> (f). (g) The merged image. (h) The DIC image of the same field shown in the (e-g). The scale bar indicates 20 μm. The white arrowhead indicates an ASI neuron. The white arrow indicates an ASJ neuron. The pink arrowhead indicates an unidentified neuron.</p