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[
Curr Biol,
2009]
The oocyte-to-embryo transition requires drastic reorganizations within a short timeframe. Recent studies show that, in the nematode Caenorhabditis elegans, phosphotyrosine-binding pseudo-phosphatases are key regulators of this critical developmental transition.
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Worm,
2016]
In eukaryotic organisms, gene regulation occurs in the context of chromatin. In the interphase nucleus, euchromatin and heterochromatin occupy distinct space during cell differentiation, with heterochromatin becoming enriched at the nuclear and nucleolar peripheries. This organization is thought to fine-tune gene expression. To elucidate the mechanisms that govern this level of genome organization, screens were carried out in C. elegans which monitored the loss of heterochromatin sequestration at the nuclear periphery. This led to the identification of a novel chromodomain protein, CEC-4 (Caenorhabditis elegans chromodomain protein 4) that mediates the anchoring of H3K9 methylation-bearing chromatin at the nuclear periphery in early to mid-stage embryos. Surprisingly, the loss of CEC-4 does not derepress genes found in heterochromatic domains, nor does it affect differentiation under standard laboratory conditions. On the other hand, CEC-4 contributes to the efficiency with which muscle differentiation is induced following ectopic expression of the master regulator, HLH-1. This is one of the first phenotypes specifically attributed to the ablation of heterochromatin anchoring.
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J Cell Biol,
2020]
The mechanisms that control how the two parental pronuclei fuse in the first mitosis of the embryo are poorly understood. In this issue, Rahman et al. (2020. J. Cell Biol.https://doi.org/10.1083/jcb.201909137) found that membrane fusion between pronuclear envelopes, followed by fenestration, promotes pronuclear fusion.
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Dev Cell,
2006]
Polarization of the C. elegans embryo depends on the sperm-contributed centrosome, which cues a retraction of the actomyosin cortex to the opposite end of the embryo by an unknown mechanism. New evidence reveals that the sperm donates a second polarizing cue that may locally relax the actomyosin cortex near the point of sperm entry.
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[
Curr Biol,
2012]
New findings reveal that, in Caenorhabditis elegans embryos, the centrosome provides signals that induce cell polarization, independently of its function as the microtubule-organizing center.
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Dev Cell,
2014]
In this issue of Developmental Cell, Singh and Pohl (2014) report that myosin II cortical flow and the midbody remnant participate in the specification of the C.elegans embryo dorsal-ventral axis.
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[
Cell,
2007]
Using live imaging and computer simulation, Kozlowski et al. (2007) show that an interplay between spindle pole movements, microtubule dynamics, and microtubule bending contribute to asymmetric spindle placement in the C. elegans embryo.
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[
Curr Biol,
2015]
A Caenorhabditis elegans mutant has been identified in which an ectopic myosin cap shifts the cleavage furrow relative to the spindle center. Surprisingly, the molecules that suppress this cap in wild-type embryos generate a cap in other asymmetrically dividing cells.
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[
Curr Biol,
2006]
A new study shows that an antagonistic force model can explain a number of complex mitotic spindle movements in the first mitosis of the Caenorhabditis elegans embryo by simply assuming that cortical force generators become increasingly persistent in their interaction with microtubules during mitosis.
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Curr Biol,
2014]
The handover from maternal to zygotic control has to be carefully orchestrated. In most animal embryos, maternal products drive early embryogenesis, and the genome of the zygote is only switched on later. However, in the nematode Ascaris the zygotic genome is never silent, and the maternal products are rapidly eliminated.